Hydraulic Brake System Buick LaCrosse I

Fastener Tightening Specifications

Fastener Tightening Specifications

Brake Component Specifications

Brake Component Specifications

Brake System Specifications

Brake System Specifications

Scheme 1

Scheme 2

Scheme 3

Hydraulic Brakes Connector End Views

Brake Fluid Level Switch Connector Part Information OEM: Assembly 15449029 Connector 15449025 PLR 15336006 Connector Seal 12040750 Service: See Catalog 2-Way F GT 150 Series Sealed (GY) Pin Wire Color Circuit No. Function A BK/WH 1551 Ground B TN/WH 33 Brake Warning Indicator Control

Park Brake Switch Connector Part Information OEM: 12004267 Service: 12102561 1-Way F 56 Series (BK) Pin Wire Color Circuit No. Function A OG/BK 233 Park Brake Switch Signal

Diagnostic Starting Point - Hydraulic Brakes

Begin the system diagnosis by reviewing the system Description and Operation. Reviewing the Description and Operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the Description and Operation information will also help you determine if the condition described by the customer is normal operation. Refer to Symptoms - Hydraulic Brakes in order to identify the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Data List

Body Control Module (BCM)

Symptoms - Hydraulic Brakes

1. Perform the «Brake System Vehicle Road Test»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) before using the hydraulic brake symptom tables in order to duplicate the customer's concern.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following: «Brake Warning System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) «Hydraulic Brake System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) «Brake Assist System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) «Disc Brake System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#disc-brake-system) in Disc Brakes

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Hydraulic Brake System. Refer to «Checking Aftermarket Accessories»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__checking-aftermarket-accessories) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Brake Warning Indicator Always On»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system)
2. «Brake Warning Indicator Inoperative»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-warning-indicator-inoperative)
3. «Brake Pulsation»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system)
4. «Brake System Noise»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-system-noise)
5. «Braking Action Uneven - Pulls to One Side»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system)
6. «Braking Action Uneven - Front to Rear»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system)
7. «Brake Pedal Excessive Travel»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-pedal-excessive-travel)
8. «Brake Pedal Excessive Effort»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-pedal-excessive-effort)
9. «Brakes Drag»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brakes-drag)
10. «Brake System Slow Release»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-system-slow-release)
11. «Brake Fluid Loss»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-fluid-loss)

Test Description

The number below refers to the step number on the diagnostic table.

1. 7: If the fuse in the jumper opens when you perform this test, the signal circuit of the brake fluid level switch is shorted to voltage.

Brake Warning Indicator Always On

Brake Warning Indicator Inoperative

Brake Warning Indicator Inoperative

The numbers below refer to the step numbers on the diagnostic table

1. 2: Suspension components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.
2. 3: Antilock brake system operation could produce feedback through the brake pedal during application of the brake system.

Brake Pulsation

Brake System Noise

Brake System Noise

The numbers below refer to the step numbers on the diagnostic table

1. 2: Suspension components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.
2. 3: Steering components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.

Braking Action Uneven - Pulls to One Side

The number below refers to the step number on the diagnostic table

1. 2: Suspension components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.

Braking Action Uneven - Front to Rear

Brake Pedal Excessive Travel

Brake Pedal Excessive Travel

Brake Pedal Excessive Effort

Brake Pedal Excessive Effort

Brakes Drag

Brakes Drag

Brake System Slow Release

Brake System Slow Release

Brake Fluid Loss

Brake Fluid Loss

The numbers below refer to the step numbers on the diagnostic table.

1. 9: Lubricant leaks from non-brake system components may come in contact with and contaminate brake system components.
2. 10: Lubricant leaks from non-brake system components may come in contact with and contaminate brake system components.
3. 12: Disc brake rotor shields/backing plates that come in contact with disc brake rotors may cause brake system noise.

1. 15: Disc brake rotor thickness variation that exceeds the maximum acceptable level can cause brake pulsation.

1. 19: Disc brake rotor thickness variation that exceeds the maximum acceptable level can cause brake pulsation.

1. 22: Disc brake rotor assembled lateral runout (LRO) that exceeds the maximum acceptable level can lead to thickness variation.

Disc Brake System Diagnosis

Hydraulic Brake System Diagnosis

Brake Assist System Diagnosis

Brake Assist System Diagnosis

Preliminary Inspections

1. Visually inspect easily accessible brake system components for obvious damage and/or leaks which may indicate that the vehicle should not be driven until further inspections have been completed.
2. Inspect the brake master cylinder reservoir fluid level and adjust only if necessary for brake system road testing. Refer to «Master Cylinder Reservoir Filling»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__master-cylinder-reservoir-filling) .
3. Inspect the tire inflation pressures and adjust as necessary.
4. Inspect the tire tread patterns to ensure that they are the same or very similar, especially per axle.
5. Ensure that the vehicle is not loaded unevenly prior to brake system road testing.

Road Testing Procedure

1. Start the engine and allow it to idle.
2. Check to see if the brake system warning lamp remains illuminated.
3. If the brake system warning lamp remains illuminated, DO NOT proceed to test drive the vehicle until it is diagnosed and repaired. Refer to «Symptoms - Hydraulic Brakes»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__symptoms-hydraulic-brakes) .
4. Select a smooth, dry, clean and level road or large lot that is as free of traffic and obstacles as possible for brake system low speed road testing.
5. With the transmission in PARK, lightly apply the brake pedal. Observe both the pedal feel and the pedal travel.
6. If the brake pedal apply felt spongy or the pedal travel was excessive, DO NOT drive the vehicle until it is repaired.
7. If the brake pedal apply did not feel spongy and the pedal travel was not excessive, proceed to step 8.
8. Release and apply the brakes.
9. While continuing to apply the brakes, shift the transmission into DRIVE, release the brakes and allow the engine to idle the vehicle away from the stopped position. Observe for a slow release of the brake system.
10. With the aid of an assistant to observe the vehicle's performance from outside of the vehicle, drive the vehicle at a low speed and lightly apply the brakes while driving past the assistant. Have the assistant observe for brake system noise from the side of the vehicle closest to them, while you observe both the pedal effort and the pedal travel.
11. If the brake pedal apply effort was excessive or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.
12. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to step 13.
13. Drive the vehicle in the opposite direction, at the same low speed and lightly apply the brakes while driving past the assistant. Have the assistant observe for brake system noise from the side of the vehicle closest to him.
14. Drive the vehicle at a low speed and shift the transmission into NEUTRAL without applying the brakes. Observe for a rapid deceleration in vehicle speed, indicating possible brake drag.
15. Select a smooth, dry, clean and level road that is as free of heavy traffic as possible for brake system moderate speed road testing.
16. Drive the vehicle at a moderate speed. Observe for a pull and/or incorrect tracking of the vehicle without the brakes applied.
17. While continuing to drive the vehicle at a moderate speed, perform several light applies of the brakes. Observe the pedal effort and the pedal travel, observe for brake system noise, pulsation and/or brake drag.
18. If the brake pedal apply effort was excessive or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.
19. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to step 20.
20. While continuing to drive the vehicle at a moderate speed, perform several moderate applies of the brakes. Observe the pedal effort and the pedal travel, observe for brake system pulsation and/or uneven braking action - either side to side or front to rear. A small amount of vehicle front end dip is expected during a moderate apply of the brakes.
21. If the brake pedal apply effort was excessive or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.

Tools Required

J 28662 Brake Pedal Effort Gage. See Special Tools .

1. With the ignition OFF and the brakes cool, apply the brakes 3-5 times or until the brake pedal becomes firm, in order to deplete the brake booster power reserve.
2. Install the J 28662 to the brake pedal. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
3. Measure and record the distance (1) from the brake pedal to the rim of the steering wheel. Note the points of measurement.
4. Apply and maintain the brakes with 445 N (100 lb) of force to the brake pedal, as indicated on the J 28662 . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
5. While maintaining 445 N (100 lb) of force to the brake pedal, measure and record the distance (2) from the same point on the brake pedal to the same point on the rim of the steering wheel.
6. Release the brakes and repeat steps 4 and 5 to obtain a second measurement. After obtaining a second measurement, proceed to step 7.
7. Average the first and second measurements recorded during the two applies of the brakes.
8. Subtract the initial measurement, unapplied (1), from the averaged, applied measurement (2) to obtain the brake pedal travel distance. Specification: Maximum brake pedal travel - measured with the ignition OFF, brake booster power assist depleted and the brakes cool: 74 mm (2.91 in).

Brake System Vacuum Source Test (STS)

1. Disconnect the engine vacuum hose from the vacuum brake booster check valve.
2. Install a vacuum gage to the engine vacuum hose.
3. Start the engine and allow the engine to idle until normal operating temperatures are reached.
4. Check to see if the engine vacuum reading is within the specified normal engine vacuum range. Specification: 47-68 kPa (14-20 in Hg)
5. Turn the ignition OFF.
6. If the engine vacuum reading is within the specified normal range, proceed to step 10.
7. If the engine vacuum reading is NOT within the specified normal range, inspect the engine vacuum hose for the following conditions. Tight connection to the engine Collapse, deformation or contamination Cracks, cuts, dry-rot
8. If any of these conditions were found with the engine vacuum hose, replace the hose, then repeat steps 2-4.
9. If none of these conditions were found with the engine vacuum hose, then there is an engine vacuum source problem, check the engine vacuum system.
10. Remove the vacuum brake booster check valve from the booster.
11. Install the check valve to the engine vacuum hose.
12. Install the vacuum gage to the check valve.
13. Start the engine and allow the engine to idle until normal operating temperatures are reached.
14. Turn the ignition OFF.
15. Check to see if the engine vacuum reading is maintained within the specified normal engine vacuum range. Specification: 47-68 kPa (14-20 in Hg)
16. If the engine vacuum reading is maintained within the specified normal range, proceed to step 18.
17. If the engine vacuum reading is NOT maintained within the specified normal range, replace the brake booster check valve, then repeat steps 11-15.
18. Inspect the brake booster check valve grommet for the following conditions: Firm connection to the vacuum brake booster Deformation or contamination Cracks, cuts, dry-rot
19. If any of these conditions were found with the check valve grommet, replace the grommet.

Brake System External Leak Inspection

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. In order to inspect for external brake fluid leaks, first check the fluid level in the master cylinder. While a slight brake fluid level drop can be considered a normal condition due to brake lining wear, a very low level may indicate a brake fluid leak in the hydraulic system.
2. If the fluid level is abnormally low, adjust the brake fluid level. Refer to «Master Cylinder Reservoir Filling»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__master-cylinder-reservoir-filling) .
3. Start the engine and allow it to idle.
4. Apply constant, moderate foot pressure to the brake pedal. If the brake pedal gradually falls away while under foot pressure, there may be a brake fluid leak.
5. Turn OFF the ignition.
6. Visually inspect the following brake system components for brake fluid leaks, excessive corrosion and damage. Give particular attention to all brake pipe and flexible hose connections to ensure that there are not any slight brake fluid leaks - even though the brake pedal may feel firm and hold steady: Master cylinder brake pipe fittings All brake pipe connections Brake pipes Brake hoses and connections Brake calipers and/or wheel cylinders, if equipped
7. While slight dampness around the master cylinder reservoir can be considered acceptable, brake fluid leaking from any of the brake system components requires immediate attention. If any of these components exhibit signs of brake fluid leakage, repair or replace those components. After the repair or replacement, reinspect the hydraulic brake system to assure proper function.

Brake System Internal Leak Test

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. Start the engine and allow it to idle.
2. Apply light, steady pressure to the brake pedal. Observe both the brake pedal feel and travel.
3. Release the brakes and turn OFF the ignition.
4. If the brake pedal apply felt spongy, but the brake pedal travel was not excessive, perform the following steps: Inspect the brake system for external leaks. Refer to «Brake System External Leak Inspection»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-system-external-leak-inspection) . Pressure bleed the brake system in order to purge any air that may be trapped in the system. Refer to «Hydraulic Brake System Bleeding (Manual)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) and «Hydraulic Brake System Bleeding (Pressure)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
5. If the brake pedal apply did not feel spongy, but the brake pedal travel was excessive, perform the following steps: Loosen the master cylinder-to-brake power booster mounting nuts. Carefully pull the master cylinder away from the brake power booster just enough to inspect the mounting surface of the master cylinder. Inspect the master cylinder mounting surface at the primary piston (2) for brake fluid leaks.
6. If the master cylinder exhibits any leakage around the primary piston (2), then the primary piston primary seal (4) and/or secondary seal (3) is leaking and the master cylinder requires overhaul or replacement.
7. If the master cylinder primary piston (2) does not exhibit any leakage, pressure bleed the brake system. Refer to «Hydraulic Brake System Bleeding (Manual)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) or «Hydraulic Brake System Bleeding (Pressure)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
8. If the brake pedal apply did not feel spongy, the brake pedal travel was initially steady and not excessive, but then gradually fell, then the master cylinder requires overhaul or replacement due to an internal leak past the secondary piston (1) from the secondary piston primary seal (6) or secondary seal (5).
9. If the brake pedal apply did not feel spongy, the brake pedal travel was initially steady and not excessive, then fell slightly, then became steady again, then the brake pressure modulator valve (BPMV) may be leaking internally and may require replacement.

Hydraulic Brake Component Operation Visual Inspection

1. With the tire and wheel assemblies removed and the brake rotors retained by wheel lug nuts, visually inspect the caliper piston dust boot (2) sealing area to ensure that there are no brake fluid leaks.
2. If any evidence of a brake fluid leak is present, the brake caliper requires overhaul or replacement.
3. While the brake system is at rest (4), observe the position of the caliper piston (1) in relation to the caliper housing.
4. Have an assistant apply and release the brake pedal several times while you observe the operation of the hydraulic brake caliper. Observe the caliper piston (1) for unrestricted and even movement during each apply of the brake system (5). Observe the caliper piston (1) for an unrestricted and even return motion during each release of the brake system (6).
5. If the caliper piston (1) did not exhibit unrestricted and even movement during brake system apply and/or release, the piston square seal (3) may be worn or damaged and the caliper may require overhaul or replacement.

Brake Pipe and Hose Inspection

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. Visually inspect all of the brake pipes for the following conditions: Kinks, improper routing, missing or damaged retainers Leaking fittings, excessive corrosion
2. If any of the brake pipes exhibited any of the conditions listed, then the identified pipe or pipes, require replacement.
3. Ensure that the vehicle axles are properly supported at ride height in order to maintain the proper relationship of the flexible brake hoses to the chassis.
4. Visually inspect all of the flexible brake hoses for the following conditions: Kinks (1), improper routing, twists, chafing, missing or damaged retainers Leaking connections, cracking, dry-rot, blisters, bulges
5. If any of the flexible brake hoses exhibited any of the conditions listed, then the identified flexible brake hose or hoses require replacement.
6. Squeeze the flexible brake hoses with firm finger pressure to check for soft spots (2), indicating an internal restriction. Check the entire length of each flexible brake hose.
7. If any of the flexible brake hoses were found to have soft spots (2), then the identified flexible brake hose or hoses require replacement.

Brake Pedal Pushrod Inspection

1. Disconnect the brake pedal pushrod (1) from the brake pedal.
2. Inspect the brake pedal pushrod eyelet bushing (2), if equipped, for cracks and/or excessive wear.
3. Reposition the pedal pushrod boot (3) toward the front of the vehicle to expose as much of the pedal pushrod (1) as possible.
4. Inspect the brake pedal pushrod (1) for straightness.
5. If the brake pedal pushrod eyelet bushing (2) exhibited cracks and/or excessive wear, then the bushing requires replacement.
6. If the brake pedal pushrod (1) is not straight, then the pushrod requires replacement.
7. Return the pedal pushrod boot (3) to its original position on the pedal pushrod (1).
8. Connect the brake pedal pushrod (1) to the brake pedal.

Master Cylinder Reservoir Filling

Note. When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. Visually inspect the brake fluid level through the brake master cylinder reservoir.
2. If the brake fluid level is at or below the half-full point during routine fluid checks, the brake system should be inspected for wear and possible brake fluid leaks.
3. If the brake fluid level is at or below the half-full point during routine fluid checks and an inspection of the brake system did not reveal wear or brake fluid leaks, the brake fluid may be topped-off up to the maximum-fill level.
4. If brake system service was just completed, the brake fluid may be topped-off up to the maximum-fill level.
5. If the brake fluid level is above the half-full point, adding brake fluid is not recommended under normal conditions.
6. If brake fluid is to be added to the master cylinder reservoir, clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm. Use only Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.

Removal Procedure

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. Remove the master cylinder from the vehicle. Refer to «Master Cylinder Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
2. Secure the master cylinder in a vise. Do not clamp the master cylinder body, secure only at the flange.
3. Remove the brake fluid level sensor. Using needle nose pliers, carefully depress the retaining tabs on the end of the brake fluid level sensor (1) and press the sensor through the reservoir to remove.
4. Carefully tap out the reservoir retaining pins.
5. Remove the reservoir from the master cylinder by pulling the reservoir straight up and away from the cylinder.
6. Remove the seals from the master cylinder.

Installation Procedure

1. Inspect the reservoir (1) for cracks or deformation. If found, replace the reservoir.
2. Clean the reservoir with denatured alcohol or equivalent.
3. Dry the reservoir with non-lubricated, filtered air.
4. Lubricate the new seals (2) and the outer surface area of the reservoir-to-housing barrels with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
5. Install the lubricated seals (2), make sure they are fully seated.
6. Install the reservoir (1) to the master cylinder, by pressing the reservoir straight down on the master cylinder until the pin holes are aligned.
7. Carefully tap the reservoir retaining pins into place to secure the reservoir.
8. Place the brake fluid level sensor into the reservoir, press into place to secure the sensor retaining tabs.
9. Remove the master cylinder from the vise.
10. Install master cylinder to the vehicle. Refer to «Master Cylinder Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. Disconnect the electrical connector from the brake fluid level sensor.
2. Disconnect the brake pipes from the master cylinder.
3. Plug the open brake pipe ends.
4. Remove master cylinder mounting nuts.
5. Remove the master cylinder from the vehicle.
6. Drain the master cylinder reservoir of all brake fluid.

1. Bench bleed the master cylinder. Refer to «Master Cylinder Bench Bleeding»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__master-cylinder-bench-bleeding) .
2. Install the master cylinder to the vacuum brake booster.
3. Install the master cylinder mounting nuts. Tighten: Tighten the master cylinder mounting nuts to 33 N.m (24 lb ft).
4. Remove the plugs from the brake pipes
5. Connect the brake pipes to the master cylinder. Tighten: With ABS tighten the brake pipe fittings at the master cylinder to 30 N.m (22 lb ft). Without ABS tighten the front brake fittings to 27 N.m (20 lb ft). Without ABS tighten the rear brake fittings to 25 N.m (18 lb ft).
6. Connect the electrical connector to the brake fluid level sensor.
7. Bleed the brake system. Refer to «Hydraulic Brake System Bleeding (Manual)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) or «Hydraulic Brake System Bleeding (Pressure)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .

Master Cylinder Overhaul

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

Disassembly Procedure

1. Remove the brake master cylinder from the vehicle. Refer to «Master Cylinder Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
2. Secure the mounting flange of the brake master cylinder in a bench vise so that the rear of the primary piston is accessible.
3. Clean the outside of the master cylinder reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
4. Remove the reservoir cap and diaphragm from the reservoir.
5. Inspect the reservoir cap and diaphragm for the following conditions. If any of these conditions are present, replace the affected components. Cuts or cracks Nicks or deformation
6. Remove the master cylinder reservoir from the master cylinder. Refer to «Master Cylinder Reservoir Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
7. Using a smooth, round-ended tool, depress the primary piston (2) and remove the piston retainer.
8. Remove the primary piston assembly from the cylinder bore.
9. Plug the cylinder inlet ports and the rear outlet port. Apply low pressure, non-lubricated, filtered air into the front outlet port, in order the remove the secondary piston (1) with the primary (6) and secondary (5) seals and the return spring.
10. Discard the primary piston assembly, the piston retainer and the seals and seal retainer from the secondary piston.

Assembly Procedure

1. Clean the interior and exterior of the master cylinder, the secondary piston (1) and the return spring in denatured alcohol or equivalent.
2. Inspect the master cylinder bore, inlet and outlet ports, the secondary piston (1), the return spring for cracks, scoring, pitting, and/or corrosion. Replace the master cylinder if any of these conditions exist.
3. Dry the master cylinder and the individual components with non-lubricated, filtered air.
4. Lubricate the master cylinder bore, the secondary piston (1), the return spring and all of the individual overhaul components with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
5. Assemble the lubricated, new primary seal (6), retainer, and new secondary seal (5) onto the secondary piston.
6. Install the lubricated return spring and secondary piston assembly (1) into the cylinder bore.
7. Install the lubricated, new primary piston assembly (2) into the cylinder bore.
8. Using a smooth, round-ended tool, depress the primary piston (2) and install the new piston retainer.
9. Install the master cylinder reservoir to the master cylinder. Refer to «Master Cylinder Reservoir Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
10. Install the reservoir cap and diaphragm to the reservoir.
11. Install the master cylinder to the vehicle. Refer to «Master Cylinder Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .

Master Cylinder Bench Bleeding

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

Note. When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

1. Secure the mounting flange of the brake master cylinder in a bench vise so that the rear of the primary piston is accessible.
2. Remove the master cylinder reservoir cap and diaphragm.
3. Install suitable fittings to the master cylinder ports that match the type of flare seat required and also provide for hose attachment.
4. Install transparent hoses to the fittings installed to the master cylinder ports, then route the hoses into the master cylinder reservoir.
5. Fill the master cylinder reservoir to at least the half-way point with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
6. Ensure that the ends of the transparent hoses running into the master cylinder reservoir are fully submerged in the brake fluid.
7. Using a smooth, round-ended tool, depress and release the primary piston as far as it will travel, a depth of about 25 mm (1 in), several times. Observe the flow of fluid coming from the ports. As air is bled from the primary and secondary pistons, the effort required to depress the primary piston will increase and the amount of travel will decrease.
8. Continue to depress and release the primary piston until fluid flows freely from the ports with no evidence of air bubbles.
9. Remove the transparent hoses from the master cylinder reservoir.
10. Install the master cylinder reservoir cap and diaphragm.
11. Remove the fittings with the transparent hoses from the master cylinder ports. Wrap the master cylinder with a clean shop cloth to prevent brake fluid spills.
12. Remove the master cylinder from the vise.

1. Disconnect the electrical connector from brake fluid level sensor.
2. Remove the brake fluid level sensor. Using needle nose pliers, carefully depress the retaining tabs on the end of the brake fluid level sensor (1) and press the sensor through the reservoir to remove.

1. Place the brake fluid level sensor (1) into the reservoir, press into place to secure the sensor retaining tabs.
2. Connect the electrical connector to the brake fluid level sensor (1).

1. Remove the left instrument panel insulator.
2. Push the BCM up and move the bottom of the BCM away from and out of the mounting bracket slot. Position the BCM aside.
3. Remove the stoplamp switch. Refer to «Brake Pedal Position Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/exterior-lights/#lighting-systems__brake-pedal-position-sensor-replacement) .
4. Remove the cruise control release switch, if equipped.
5. Release the wiring harness clips from the bracket.
6. Remove the brake pedal pushrod retaining clip from the brake pedal.
7. Remove the brake pedal pushrod and washer from the brake pedal.
8. Remove the brake pedal nut and bolt.
9. Remove the brake pedal and bushings.

1. Install the brake pedal and bushings.
2. Install the brake pedal nut and bolt. Tighten: Tighten the brake pedal nut and bolt to 40 N.m (30 lb ft).
3. Install the brake pedal washer and pushrod to the brake pedal.
4. Install the brake pedal pushrod retaining clip to the brake pedal.
5. Secure the wiring harness clips to the bracket.
6. Install the cruise control release switch, if equipped.
7. Install the stoplamp switch. Refer to «Brake Pedal Position Sensor Replacement»(/buick/lacrosse/i-2004-2009/remont/exterior-lights/#lighting-systems__brake-pedal-position-sensor-replacement) .
8. Insert the top of the BCM up into the mounting bracket, then engage the bottom of the BCM into the mounting bracket slot.
9. Install the left instrument panel insulator.

J 45405 Pipe Flaring Tool Kit. See Special Tools .

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

Replacement Procedure

1. Inspect the section of brake pipe to be replaced.
2. Release the brake pipe to be replaced from the retainers, as required.
3. Select an appropriate location to section the brake pipe, if necessary. Allow adequate clearance in order to maneuver the J 45405 . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) . Avoid sectioning the brake pipe at bends or mounting points.
4. Using a string or wire, measure the length of the pipe to be replaced including all pipe bends.
5. Add to the measurement taken the appropriate additional length required for each flare to be created. Specification: 6.35 mm (0.250 in) for 4.76 mm (3/16 in) diameter pipe IMPORTANT: Ensure that the brake pipe end to be flared is cut at a square, 90 degree angle to the pipe length.
6. Using the pipe cutter included in the J 45405 , carefully cut the brake pipe squarely to the measured length. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
7. Remove the sectioned brake pipe from the vehicle.
8. Select the appropriate size of brake pipe and tube nuts, as necessary. The brake pipe outside diameter determines brake pipe size.
9. Strip the nylon coating from the brake pipe ends to be flared, if necessary. Select the appropriate blade on the coating stripping tool included in the J 45405 , by unthreading the blade block from the stripping tool and installing the block with the desired blade facing the tool rollers. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) . Specification: 6.35 mm (0.250 in) blade for 4.76 mm (3/16 in) diameter pipe Insert the brake pipe end to be flared into the stripping tool to the depth of the ledge on the tool rollers. While holding the brake pipe firmly against the stripping tool roller ledges, rotate the thumbwheel of the tool until the blade contacts the brake pipe coated surface. IMPORTANT: Do not gouge the metal surface of the brake pipe. Rotate the stripping tool in a clockwise direction, ensuring that the brake pipe end remains against the tool roller ledges. After each successive revolution of the stripping tool, carefully rotate the thumbwheel of the tool clockwise, in order to continue stripping the coating from the brake pipe until the metal pipe surface is exposed. Loosen the thumbwheel of the tool and remove the brake pipe. IMPORTANT: Ensure that all loose remnants of the nylon coating have been removed from the brake pipe. Inspect the stripped end of the brake pipe to ensure that the proper amount of coating has been removed. Specification: 6.35 mm (0.250 in) for 4.76 mm (3/16 in) diameter pipe
10. Chamfer the inside and outside diameter of the pipe with the de-burring tool included in the J 45405 . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
11. Install the tube nuts on the brake pipe, noting their orientation.
12. Clean the brake pipe and the J 45405 of lubricant, contaminants and debris. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
13. Loosen the die clamping screw of the J 45405 . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
14. Select the corresponding die set and install the die halves into the die cage with the full, flat face of one die facing the clamping screw and the counterbores of both dies facing the forming ram.
15. Place the flat face of an unused die (1) against the die halves in the clamping cage and hold firmly against the counterbored face of the dies.
16. Insert the prepared end of the pipe to be flared through the back of the dies until the pipe is seated against the flat surface of the unused die (1).
17. Remove the unused die (1).
18. Ensure that the rear of both dies are seated firmly against the enclosed end of the die cage.
19. Firmly hand tighten the clamping screw (2) against the dies.
20. Select the appropriate forming mandrel and place into the forming ram.
21. Rotate the hydraulic fluid control valve clockwise to the closed position.
22. Rotate the body of the J 45405 until it bottoms against the die cage. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
23. While guiding the forming mandrel into the exposed end of pipe to be flared, operate the lever of the J 45405 until the forming mandrel bottoms against the clamping dies. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
24. Rotate the hydraulic fluid control valve counterclockwise to the open position to allow the hydraulic forming ram to retract.
25. Loosen the die clamping screw and remove the dies and pipe.
26. If necessary, lightly tap the dies until the die halves separate.
27. Inspect the brake pipe flare for correct shape and diameter (a). Specification: 7.10 mm (0.279 in) +/- 0.18 mm (0.007 in) flare diameter for 4.76 mm (3/16 in) diameter pipe
28. If necessary, using the removed section of pipe as a template, shape the new pipe with a suitable brake pipe bending tool. IMPORTANT: When installing the pipe, maintain a clearance of 19 mm (3/4 in) from all moving or vibrating components.
29. Install the pipe to the vehicle with the appropriate brake pipe unions as required.
30. If previously released, secure the brake pipe to the retainers.
31. Bleed the hydraulic brake system. Refer to «Hydraulic Brake System Bleeding (Manual)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) or «Hydraulic Brake System Bleeding (Pressure)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
32. With the aid of an assistant, inspect the brake pipe flares for leaks by starting the engine and applying the brakes.

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. Raise and suitably support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
2. Remove the front tire and wheel assembly. Refer to «Tire and Wheel Removal and Installation»(/buick/lacrosse/i-2004-2009/remont/wheel-tire-system/#tires-and-wheels) in Tires and Wheels.
3. Clean all dirt and foreign material from the brake hoses and brake pipe fitting.
4. Use a backup wrench on the hose fitting, disconnect the brake pipe fitting from the brake hose, then cap or plug the brake pipe fitting end. Do not bend the brake pipe or the bracket.
5. Remove the brake hose retaining clip from the hose mounting bracket.
6. Remove the hose from the bracket.
7. Remove the brake hose to caliper bolt (4) from the brake caliper (2).
8. Remove the brake hose (5) from the brake caliper (2).
9. Remove and discard the two copper brake hose gaskets (3). These gaskets may be stuck to the brake caliper and/or the brake hose end.

1. Assemble the NEW copper brake hose gaskets (3) and the brake hose bolt (4) to the brake hose.
2. Install the brake hose to caliper bolt to the brake caliper. Tighten: Tighten the brake hose to brake caliper bolt to 54 N.m (40 lb ft).
3. With the weight of the vehicle on the suspension, install the brake hose into the bracket. There should not be any kinks in the hose. Align the hose fitting with the notch in the bracket. Use the hose paint stripe as a visual aid.
4. Install the retainer onto the hose fitting at the bracket.
5. Remove the rubber cap or plug from the exposed brake pipe fitting end.
6. Connect the brake pipe fitting to the brake hose: Use a backup wrench on the hose fitting. Do not bend the bracket or pipe. Tighten: Tighten the brake pipe fitting to 18 N.m (13 lb ft).
7. Install the front tire and wheel assembly. Refer to «Tire and Wheel Removal and Installation»(/buick/lacrosse/i-2004-2009/remont/wheel-tire-system/#tires-and-wheels) in Tires and Wheels.
8. Ensure that the hose does not make contact with any part of the suspension. Check the hose in extreme right and extreme left turn conditions. If the hose makes contact, remove the hose and correct the condition.
9. Bleed the hydraulic brake system. Refer to «Hydraulic Brake System Bleeding (Manual)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) or «Hydraulic Brake System Bleeding (Pressure)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
10. Lower the vehicle.

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice .

1. Raise and suitably support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/buick/lacrosse/i-2004-2009/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) .
2. Remove the rear tire and wheel assembly. Refer to «Tire and Wheel Removal and Installation»(/buick/lacrosse/i-2004-2009/remont/wheel-tire-system/#tires-and-wheels) .
3. Clean all dirt and foreign material from the brake hoses and brake pipe fitting.
4. Use a backup wrench on the hose fitting, disconnect the brake pipe fitting from the brake hose, then cap or plug the brake pipe fitting end. Do not bend the brake pipe or the bracket.
5. Remove the brake hose retaining clip from the hose mounting bracket.
6. Remove the hose from the bracket.
7. Remove the brake hose to caliper bolt (1) from the brake caliper.
8. Remove the brake hose (2) from the brake caliper.
9. Remove the brake hose from the vehicle.
10. Remove and discard the two copper brake hose gaskets (4). These gaskets may be stuck to the brake caliper and/or the brake hose end.

1. Position the brake hose in the vehicle.
2. Assemble the NEW copper brake hose gaskets (4) and the brake hose bolt (1) to the brake hose (2).
3. Install the brake hose to caliper bolt (1) to the brake caliper. While installing the right rear brake hose to caliper, hold up while tightening bolt. Tighten: Tighten the brake hose to brake caliper bolt to 54 N.m (40 lb ft).
4. With the weight of the vehicle on the suspension, install the brake hose into the bracket. There should not be any kinks in the hose. Align the hose fitting with the notch in the bracket. Use the hose paint stripe as a visual aid.
5. Install the retainer onto the hose fitting at the bracket.
6. Remove the rubber cap or plug from the exposed brake pipe fitting end.
7. Connect the brake pipe fitting to the brake hose: Use a backup wrench on the hose fitting. Do not bend the bracket or pipe. Tighten: Tighten the brake pipe fitting to 18 N.m (13 lb ft).
8. Install the rear tire and wheel assembly. Refer to «Tire and Wheel Removal and Installation»(/buick/lacrosse/i-2004-2009/remont/wheel-tire-system/#tires-and-wheels) .
9. Ensure that the hose does not make contact with any part of the suspension. If the hose makes contact, remove the hose and correct the condition.
10. Bleed the hydraulic brake system. Refer to «Hydraulic Brake System Bleeding (Manual)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) or «Hydraulic Brake System Bleeding (Pressure)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .
11. Lower the vehicle.

Note. When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
2. With the ignition OFF and the brakes cool, apply the brakes 3-5 times or until the brake pedal effort increases significantly, in order to deplete the brake booster power reserve.
3. If you have performed a brake master cylinder bench bleeding on this vehicle or if you disconnected the brake pipes from the master cylinder, you must perform the following steps: Ensure that the brake master cylinder reservoir is full to the maximum-fill level. If necessary, add Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. If removal of the reservoir cap and diaphragm is necessary, clean the outside of the reservoir on and around the cap prior to removal. With the rear brake pipe installed securely to the master cylinder, loosen and separate the front brake pipe from the front port of the brake master cylinder. Allow a small amount of brake fluid to gravity bleed from the open port of the master cylinder. Reconnect the brake pipe to the master cylinder port and tighten securely. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal. Loosen the same brake pipe to purge air from the open port of the master cylinder. Tighten the brake pipe, then have the assistant slowly release the brake pedal. Wait 15 seconds, then repeat steps 3.3-3.7 until all air is purged from the same port of the master cylinder. With the front brake pipe installed securely to the master cylinder, after all air has been purged from the front port of the master cylinder, loosen and separate the rear brake pipe from the master cylinder, then repeat steps 3.3-3.8. After completing the final master cylinder port bleeding procedure, ensure that both of the brake pipe-to-master cylinder fittings are properly tightened.
4. Fill the brake master cylinder reservoir with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. Ensure that the brake master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
5. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
6. Install a transparent hose over the end of the bleeder valve.
7. Submerge the open end of the transparent hose into a transparent container partially filled with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
8. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
9. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
10. Tighten the bleeder valve, then have the assistant slowly release the brake pedal.
11. Wait 15 seconds, then repeat steps 8-10 until all air is purged from the same wheel hydraulic circuit.
12. With the right rear wheel hydraulic circuit bleeder valve tightened securely, after all air has been purged from the right rear hydraulic circuit, install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit bleeder valve.
13. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
14. With the left front wheel hydraulic circuit bleeder valve tightened securely, after all air has been purged from the left front hydraulic circuit, install a proper box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve.
15. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
16. With the left rear wheel hydraulic circuit bleeder valve tightened securely, after all air has been purged from the left rear hydraulic circuit, install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve.
17. Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
18. After completing the final wheel hydraulic circuit bleeding procedure, ensure that each of the 4 wheel hydraulic circuit bleeder valves are properly tightened.
19. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
20. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
21. If the brake pedal feels spongy, repeat the bleeding procedure again. If the brake pedal still feels spongy after repeating the bleeding procedure, perform the following steps: Inspect the brake system for external leaks. Refer to «Brake System External Leak Inspection»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-system-external-leak-inspection) . Pressure bleed the hydraulic brake system in order to purge any air that may still be trapped in the system.
22. Turn the ignition key ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.
23. If the brake system warning lamp remains illuminated, refer to «Symptoms - Hydraulic Brakes»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__symptoms-hydraulic-brakes) .

1. J 29532 Diaphragm Type Brake Pressure Bleeder or equivalent. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
2. J 35589-A Master Cylinder Bleeder Adapter. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .

Bleeding Procedure

Note. When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

1. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
2. With the ignition OFF and the brakes cool, apply the brakes 3-5 times or until the brake pedal effort increases significantly, in order to deplete the brake booster power reserve.
3. If you have performed a brake master cylinder bench bleeding on this vehicle or if you disconnected the brake pipes from the master cylinder, you must perform the following steps: Ensure that the brake master cylinder reservoir is full to the maximum-fill level. If necessary, add Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. If removal of the reservoir cap and diaphragm is necessary, clean the outside of the reservoir on and around the cap prior to removal. With the rear brake pipe installed securely to the master cylinder, loosen and separate the front brake pipe from the front port of the brake master cylinder. Allow a small amount of brake fluid to gravity bleed from the open port of the master cylinder. Reconnect the brake pipe to the master cylinder port and tighten securely. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal. Loosen the same brake pipe to purge air from the open port of the master cylinder. Tighten the brake pipe, then have the assistant slowly release the brake pedal. Wait 15 seconds, then repeat steps 3.3-3.7 until all air is purged from the same port of the master cylinder. With the front brake pipe installed securely to the master cylinder, after all air has been purged from the front port of the master cylinder, loosen and separate the rear brake pipe from the master cylinder, then repeat steps 3.3-3.8. After completing the final master cylinder port bleeding procedure, ensure that both of the brake pipe-to-master cylinder fittings are properly tightened.
4. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
5. Install the J 35589-A to the brake master cylinder reservoir. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
6. Check the brake fluid level in the J 29532 or equivalent. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) . Add Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container as necessary to bring the level to approximately the half-full point.
7. Connect the J 29532 or equivalent, to the J 35589-A . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
8. Charge the J 29532 or equivalent, air tank to 175-205 kPa (25-30 psi). See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
9. Open the J 29532 or equivalent, fluid tank valve to allow pressurized brake fluid to enter the brake system. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
10. Wait approximately 30 seconds, then inspect the entire hydraulic brake system in order to ensure that there are no existing external brake fluid leaks. Any brake fluid leaks identified require repair prior to completing this procedure.
11. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
12. Install a transparent hose over the end of the bleeder valve.
13. Submerge the open end of the transparent hose into a transparent container partially filled with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
14. Loosen the bleeder valve to purge air from the wheel hydraulic circuit. Allow fluid to flow until air bubbles stop flowing from the bleeder, then tighten the bleeder valve.
15. With the right rear wheel hydraulic circuit bleeder valve tightened securely, after all air has been purged from the right rear hydraulic circuit, install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit bleeder valve.
16. Install a transparent hose over the end of the bleeder valve, then repeat steps 13-14.
17. With the left front wheel hydraulic circuit bleeder valve tightened securely, after all air has been purged from the left front hydraulic circuit, install a proper box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve.
18. Install a transparent hose over the end of the bleeder valve, then repeat steps 13-14.
19. With the left rear wheel hydraulic circuit bleeder valve tightened securely, after all air has been purged from the left rear hydraulic circuit, install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve
20. Install a transparent hose over the end of the bleeder valve, then repeat steps 13-14.
21. After completing the final wheel hydraulic circuit bleeding procedure, ensure that each of the 4 wheel hydraulic circuit bleeder valves are properly tightened.
22. Close the J 29532 or equivalent, fluid tank valve, then disconnect the J 29532 or equivalent, from the J 35589-A . See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
23. Remove the J 35589-A from the brake master cylinder reservoir. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
24. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
25. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
26. If the brake pedal feels spongy, perform the following steps: Inspect the brake system for external leaks. Refer to «Brake System External Leak Inspection»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__brake-system-external-leak-inspection) . Using a scan tool, perform the antilock brake system automated bleeding procedure to remove any air that may have been trapped in the BPMV. Refer to «ABS Automated Bleed Procedure»(/buick/lacrosse/i-2004-2009/remont/anti-locktraction-control/#antilock-brake-system-with-traction-control-system-stability-control-system) in Antilock Brake System.
27. Turn the ignition key ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.
28. If the brake system warning lamp remains illuminated, refer to «Symptoms - Hydraulic Brakes»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__symptoms-hydraulic-brakes) .

Note. Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

Note. When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

1. Inspect the brake fluid for the following conditions, indicating brake fluid contamination: Fluid separation, indicating two types of fluid are present; a substance other than the recommended brake fluid has been introduced into the brake hydraulic system Swirled appearance - oil-based substance Layered appearance - silicone-based substance Fluid discoloration, indicating the presence of moisture or particles that have been introduced into the brake hydraulic system Cloudy appearance - moisture Dark appearance/suspended particles in fluid - dirt, rust, corrosion, brake dust
2. Inspect the master cylinder reservoir cap diaphragm and the reservoir-to-master cylinder grommets for swelling, indicating brake fluid contamination.
3. If the brake fluid WAS contaminated with an oil-based or a silicone-based substance, indicated by fluid separation and/or a swollen master cylinder reservoir cap diaphragm and/or swollen reservoir-to-master cylinder grommets, perform the following: Remove ALL of the following components listed from the vehicle. Each component contains internal rubber seals/linings which have been contaminated by the contaminated brake fluid in the brake hydraulic system. Refer to the procedures indicated: «Master Cylinder Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) «Brake Hose Replacement - Front»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) «Brake Hose Replacement - Rear»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) «Brake Caliper Replacement - Front (J65, JL9)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#disc-brake-system) in Disc Brakes «Brake Caliper Replacement - Rear (J65, JL9)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#disc-brake-system__brake-caliper-replacement-rear-j65) in Disc Brakes «Brake Pressure Modulator Valve (BPMV) Replacement»(/buick/lacrosse/i-2004-2009/remont/anti-locktraction-control/#antilock-brake-system-with-traction-control-system-stability-control-system) in Antilock Brake System Clean out all the hydraulic brake pipes using denatured alcohol or equivalent. Dry the brake pipes using non-lubricated, filtered air. Repair or replace ALL of the following components listed and install them to the vehicle. Each component contains internal rubber seals/linings which have been contaminated by the contaminated brake fluid in the brake hydraulic system. Refer to the procedures indicated: «Master Cylinder Overhaul»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__master-cylinder-overhaul) or «Master Cylinder Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) ; also perform the following: Clean the brake master cylinder reservoir using denatured alcohol or equivalent, then dry the reservoir using non-lubricated, filtered air. Inspect the reservoir for cracks and/or damage and replace if necessary. Refer to «Master Cylinder Reservoir Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) . Replace the brake master cylinder reservoir cap diaphragm. «Brake Hose Replacement - Front»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) «Brake Hose Replacement - Rear»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) «Brake Caliper Overhaul - Front»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#disc-brake-system__brake-caliper-overhaul-front) or «Brake Caliper Replacement - Front (J65, JL9)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#disc-brake-system) in Disc Brakes «Brake Caliper Overhaul - Rear»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#disc-brake-system) or «Brake Caliper Replacement - Rear (J65, JL9)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#disc-brake-system__brake-caliper-replacement-rear-j65) in Disc Brakes «Brake Pressure Modulator Valve (BPMV) Replacement»(/buick/lacrosse/i-2004-2009/remont/anti-locktraction-control/#antilock-brake-system-with-traction-control-system-stability-control-system) in Antilock Brake System
4. If the brake fluid was NOT contaminated with an oil-based or a silicone-based substance, but WAS contaminated with water or dirt, rust, corrosion, and/or brake dust, replace the brake master cylinder reservoir cap diaphragm. The diaphragm may have allowed the moisture or particles to enter the hydraulic system.
5. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11®, GM P/N 12377967 (Canada P/N 992667) or equivalent, DOT-3 brake fluid from a clean, sealed brake fluid container.
6. Pressure bleed the hydraulic brake system. Begin the procedure with the pressure bleeder reservoir filled to the maximum-fill level with the correct brake fluid as indicated. Refer to «Hydraulic Brake System Bleeding (Manual)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) or «Hydraulic Brake System Bleeding (Pressure)»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) .

J 22805-B Power Brake Booster Holder. See Special Tools .

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. Remove the left instrument panel insulator. Refer to «Closeout/Insulator Panel Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
3. Remove the retaining clip and disconnect the brake booster pushrod from the brake pedal.
4. Remove the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
5. Disconnect the brake fluid level sensor electrical connector from the brake fluid level sensor.
6. Remove the 2 master cylinder retaining nuts and position the master cylinder aside.
7. Disconnect the vacuum brake booster check valve from the brake booster. Position aside the vacuum hose and the check valve as an assembly.
8. Rotate the engine forward for service access. Refer to «Rotating the Engine for Service Access»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
9. Remove the EGR valve wiring harness heat shield.
10. Remove the EGR valve. Refer to «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) in Engine Controls - 3.8L.
11. Remove the transmission fluid filler tube bracket retainer and position the filler tube aside. Refer to «Fluid Filler Tube Replacement»(/buick/lacrosse/i-2004-2009/remont/automatic-trans/#automatic-transaxle-4t65-e-introduction-2-of-2) in Automatic Transaxle - 4T65-E.
12. Remove the BPMV. Refer to «Brake Pressure Modulator Valve (BPMV) Bracket Replacement»(/buick/lacrosse/i-2004-2009/remont/anti-locktraction-control/#antilock-brake-system-with-traction-control-system-stability-control-system) in Antilock Brake System.
13. Attach the J 22805-B to the booster using the master cylinder retaining nuts. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
14. Unlock the booster from the front of the cowl. Use a flat bladed tool to depress the brake booster locking tab (1) out of the cowl mounting flange, while turning the booster counterclockwise with a ratchet on the J 22805-B (2). See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
15. Remove the vacuum brake booster.
16. Remove the J 22805-B (2) from the booster. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .

Note. Internal components of this booster are not serviceable. The housing must not be unstaked and separated. Separating the housing will cause permanent deformation, preventing the booster from holding proper volume.

Note. Inspect the locking flanges on booster and mounting plate. Replace the booster and mounting plate if the locking flanges are bent or damaged.

1. Install the vacuum brake booster. Position the vacuum brake booster on the cowl counterclockwise from the final installation position so that the locking flanges on the vacuum brake booster and on the cowl mounting flange engage.
2. Turn the vacuum brake booster clockwise with a ratchet on the J 22805-B (2). See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) . DO NOT use a flat bladed tool in the locking tab to install the vacuum brake booster. When the vacuum brake booster is correctly installed, the locking tab (1) slides up the flange and engages the locking notch.
3. Remove the J 22805-B (2) from the installed vacuum brake booster. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
4. Install the BPMV. Refer to «Brake Pressure Modulator Valve (BPMV) Bracket Replacement»(/buick/lacrosse/i-2004-2009/remont/anti-locktraction-control/#antilock-brake-system-with-traction-control-system-stability-control-system) in Antilock Brake System.
5. Install the transmission fluid filler tube bracket retainer and reposition the filler tube. Refer to «Fluid Filler Tube Replacement»(/buick/lacrosse/i-2004-2009/remont/automatic-trans/#automatic-transaxle-4t65-e-introduction-2-of-2) in Automatic Transaxle - 4T65-E.
6. Install the EGR valve. Refer to «Exhaust Gas Recirculation (EGR) Valve Replacement»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-38l-introduction-2-of-2) in Engine Controls - 3.8L.
7. Install the EGR valve wiring harness heat shield. Tighten: Tighten the EGR valve wiring harness heat shield nut and bolt to 10 N.m (89 lb in).
8. Return the engine to the original rest position. Install the left and right engine mount struts. Refer to «Engine Mount Strut Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) and «Engine Mount Strut Replacement - Right»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
9. Reposition and connect the vacuum hose and check valve assembly to the booster.
10. Reposition the master cylinder onto the booster and install the master cylinder retaining nuts. Tighten: Tighten the master cylinder retaining nuts to 33 N.m (24 lb ft).
11. Connect the brake fluid level sensor electrical connector to the brake fluid level sensor.
12. Install the fuel injector sight shield. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
13. Connect the brake booster pushrod to the brake pedal and install the retaining clip.
14. Install the left instrument panel insulator.
15. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.

J 22805-B Power Brake Booster Holder. See Special Tools .

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. Remove the left instrument panel insulator. Refer to «Closeout/Insulator Panel Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
3. Remove the brake apply sensor (BAS).
4. Remove the retaining clip and disconnect the brake booster pushrod from the brake pedal.
5. Remove the exhaust system crossover pipe. Refer to «Exhaust Crossover Pipe Replacement»(/buick/lacrosse/i-2004-2009/remont/exhaust/#engine-exhaust-system) .
6. Disconnect the brake fluid level sensor electrical connector from the brake fluid level sensor.
7. Remove the antilock brake system (ABS) module bracket fasteners from the left front fender.
8. Remove the ABS module bracket.
9. Remove the master cylinder mounting nuts and separate the master cylinder from the vacuum brake booster and position aside.
10. Disconnect the vacuum brake booster check valve from the brake booster. Position aside the vacuum hose and the check valve as an assembly.
11. Drain the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) .
12. Remove the coolant heater pipes from the engine.
13. Attach the J 22805-B to the booster using the master cylinder retaining nuts. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
14. Unlock the booster from the front of the cowl. Use a flat bladed tool to depress the brake booster locking tab (1) out of the cowl mounting flange, while turning the booster counterclockwise with a ratchet on the J 22805-B (2). See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
15. Remove the vacuum brake booster.
16. Remove the J 22805-B (2) from the booster. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .

Note. Internal components of this booster are not serviceable. The housing must not be unstaked and separated. Separating the housing will cause permanent deformation, preventing the booster from holding proper volume.

Note. Inspect the locking flanges on booster and mounting plate. Replace the booster and mounting plate if the locking flanges are bent or damaged.

1. Install the vacuum brake booster. Position the vacuum brake booster on the cowl counterclockwise from the final installation position so that the locking flanges on the vacuum brake booster and on the cowl mounting flange engage.
2. Turn the vacuum brake booster clockwise with a ratchet on the J 22805-B (2). See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) . DO NOT use a flat bladed tool in the locking tab to install the vacuum brake booster. When the vacuum brake booster is correctly installed, the locking tab (1) slides up the flange and engages the locking notch.
3. Remove the J 22805-B (2) from the installed vacuum brake booster. See «Special Tools»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system__special-tools) .
4. Reinstall the coolant heater pipes.
5. Reposition and connect the vacuum hose and check valve assembly to the booster.
6. Reposition the master cylinder onto the booster and install the master cylinder retaining nuts. Tighten: Tighten the master cylinder retaining nuts to 33 N.m (24 lb ft).
7. Reinstall the ABS module bracket and fasteners. Tighten: Tighten the ABS module bracket nuts to 10 N.m (7 lb ft).
8. Connect the brake fluid level sensor electrical connector to the brake fluid level sensor.
9. Reinstall the exhaust system crossover pipe. Refer to «Exhaust Crossover Pipe Replacement»(/buick/lacrosse/i-2004-2009/remont/exhaust/#engine-exhaust-system) .
10. Refill the cooling system. Refer to «Draining and Filling Cooling System (L26 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) , «Draining and Filling Cooling System (LY7 Static Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) or «Draining and Filling Cooling System (L26, LY7, GE 47716 Fill)»(/buick/lacrosse/i-2004-2009/remont/cooling-system-mechanical/#engine-cooling-system) .
11. Connect the brake booster pushrod to the brake pedal and install the retaining clip.
12. Reinstall the BAS. Tighten: Tighten the BAS bolt to 2.5 N.m (22 lb in).
13. Install the left instrument panel insulator.
14. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure (L26)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) or «Battery Negative Cable Disconnect/Connect Procedure (LY7)»(/buick/lacrosse/i-2004-2009/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.

1. Remove the fuel injector sight shield, 3.8L engine only. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.
2. Disconnect the vacuum hose from the intake manifold.
3. Disconnect the vacuum hose (2) from the vacuum brake booster check valve (1).
4. Remove the vacuum brake booster check valve (1) from the vacuum brake booster.

1. Install the vacuum brake booster check valve (1) onto the vacuum brake booster.
2. Connect the vacuum hose (2) to the vacuum brake booster (1).
3. Connect the vacuum hose to the intake manifold.
4. Install the fuel injector sight shield, 3.8L engine only. Refer to «Fuel Injector Sight Shield Replacement»(/buick/lacrosse/i-2004-2009/remont/mechanical/#engine-mechanical-38l) in Engine Mechanical - 3.8L.

Brake Fluid and Brake Fluid Handling

Note. When filling the master cylinder, use only Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT 3 brake fluid. Do not use a container which has been used for petroleum based fluids or a container which is wet with water. Petroleum based fluids will cause swelling and distortion of rubber parts in the hydraulic brake system and water will mix with brake fluid, lowering the boiling point. Keep all fluid containers capped to prevent contamination.

Note. Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers and fender covers to prevent brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills.

Note. Avoid spilling brake fluid on any of the vehicle's painted surfaces, wiring, cables or electrical connectors. Brake fluid will damage paint and electrical connections. If any fluid is spilled on the vehicle, immediately flush the area with water to minimize the potential for damage.

Note. Power steering fluid, engine oil, brake fluid or any mineral based fluids cannot be mixed. If brake seals contact power steering fluid or steering seals contact brake fluid, seal damage will result.

Brake System Indicator

The IPC illuminates the brake indicator when the following occurs

1. The body control module (BCM) detects that the park brake is engaged. The IPC receives a class 2 message from the BCM requesting illumination. If the vehicle is shifted out of park with the park brake engaged, the BCM activates an audible warning.
2. The IPC detects a low brake fluid condition (signal circuit is low).
3. The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

System Component Description

The hydraulic brake system consists of the following

System Operation

Mechanical force is converted into hydraulic pressure by the master cylinder, regulated to meet braking system demands by the pressure balance control system and delivered to the hydraulic brake wheel circuits by the pipes and flexible hoses. The wheel apply components then convert the hydraulic pressure back into mechanical force which presses linings against rotating brake system components.

The brake assist system consists of the following

Brake system input force is multiplied by the brake pedal and transferred by the pedal pushrod to the hydraulic brake master cylinder. Effort required to apply the brake system is reduced by the vacuum brake booster.

Special Tools

Special Tools Illustration Tool Number/Description J 22805-B Brake Booster Holder J 28662 Brake Pedal Effort Gauge J 29532 Diaphragm Type Brake Pressure Bleeder J 35589-A Brake Pressure Bleeder Adapter J 45405 Pipe Flaring Tool Kit

Scheme 4

Scheme 5

Scheme 6

Scheme 7

See also:
• Disc Brake System Description and Operation
• Checking Aftermarket Accessories
• Testing for Intermittent Conditions and Poor Connections
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Park Brake Warning Lamp Switch Replacement
• Body Control Module Replacement
• Instrument Panel Cluster (IPC) Replacement
• Diagnostic Starting Point - Suspension General Diagnosis
• Diagnostic Starting Point - Antilock Brake System
• Park Brake System Diagnosis
• Diagnostic Starting Point - Power Steering System (w/o Electro-Hydraulic Steering)
• Brake Pad Inspection
• Brake Pads Replacement - Rear (J65, JL9)
• Brake Caliper Replacement - Rear (J65, JL9)
• Disc Brake Mounting and Hardware Inspection - Front
• Brake Caliper Bracket Replacement - Front (J65, JL9)
• Brake Caliper Bracket Replacement - Rear (J65, JL9)
• Disc Brake Hardware Replacement - Front
• Disc Brake Hardware Replacement - Rear
• Brake Caliper Overhaul - Front
• Wheel Drive Shaft Outer Joint and Seal Replacement
• Brake Rotor Thickness Measurement
• Brake Rotor Thickness Variation Measurement
• Brake Rotor Surface and Wear Inspection
• Brake Rotor Refinishing
• Brake Rotor Replacement - Front (J65, JL9)
• Brake Rotor Replacement - Rear (J65, JL9)
• Brake Pressure Modulator Valve (BPMV) Replacement
• Lifting and Jacking the Vehicle
• Tire and Wheel Removal and Installation
• Diagnostic Starting Point - Engine Mechanical
• Brake Fluid Irritant Caution
• Brake Fluid Effects on Paint and Electrical Components Notice
• Fastener Notice
• Brake Pedal Position Sensor Replacement
• Battery Negative Cable Disconnect/Connect Procedure (L26)
• Fuel Injector Sight Shield Replacement
• Exhaust Gas Recirculation (EGR) Valve Replacement
• Fluid Filler Tube Replacement
• Exhaust Crossover Pipe Replacement
• Draining and Filling Cooling System (L26 Static Fill)
• Symptoms - Hydraulic Brakes
• Brake System Vehicle Road Test
• Brake Warning Indicator Inoperative
• Brake System Noise
• Brake Pedal Excessive Travel
• Brake Pedal Excessive Effort
• Brakes Drag
• Brake System Slow Release
• Brake Fluid Loss
• Diagnostic Starting Point - Hydraulic Brakes
• Brake Assist System Diagnosis
• Brake Pedal Pushrod Inspection
• Master Cylinder Reservoir Filling
• Master Cylinder Overhaul
• Hydraulic Brake Component Operation Visual Inspection
• Brake Pipe and Hose Inspection
• Brake System Internal Leak Test
• Brake System Vacuum Source Test (STS)
• Special Tools
• Brake System External Leak Inspection
• Master Cylinder Bench Bleeding