Disc & Drum: Diagnosis Dodge Cab & Chassis Dakota

POWER BRAKE BOOSTER FUNCTIONAL TEST

1. Start engine and check booster vacuum hose connections. A hissing noise indicates a vacuum leak. Repair any vacuum leaks before proceeding. Stop engine and shift transmission into Neutral. Pump brake pedal until all vacuum reserve in booster is depleted.
2. Hold brake pedal under light foot pressure. If pedal does not hold firm and falls away, master cylinder is faulty. If pedal holds firm, start engine and observe pedal action. If pedal falls away slightly under light foot pressure and then holds firm, go to step 3). If no pedal action is observed, power booster or vacuum check valve is faulty. Install good check valve and repeat steps.
3. With engine running, rebuild booster vacuum reserve. Release brake pedal. Increase engine speed to 1500 RPM. Close throttle and immediately turn off ignition. Wait a minimum of 90 seconds and try brake action again. Booster should provide 2 or more vacuum assisted pedal applications. If vacuum assist is not provided, perform booster and check valve vacuum tests.

POWER BRAKE BOOSTER VACUUM TEST

Connect vacuum gauge to booster check valve with "T" fitting. Start engine and run at idle speed for one minute. Clamp hose shut between vacuum source and check valve. Stop engine and observe vacuum gauge. If vacuum drops more than one in. Hg within 15 seconds, booster diaphragm or check valve is faulty.

POWER BRAKE BOOSTER CHECK VALVE TEST

Disconnect vacuum hose from check valve. Remove check valve and valve seal from booster. Use a hand operated vacuum pump for testing. Apply 15-20 in. Hg vacuum at large end of check valve. Vacuum should hold steady. If gauge on pump indicates vacuum loss, check valve is faulty and should be replaced.

COMBINATION VALVE METERING VALVE TEST

Metering valve operation can be checked visually with the aid of an assistant. While an assistant applies and releases the brake pedal, observe metering valve stem. If valve is operating correctly, stem will extend slightly when brakes are applied and contract when brakes are released. If valve is faulty, replace combination valve assembly.

COMBINATION VALVE PRESSURE DIFFERENTIAL SWITCH TEST

1. Have an assistant in vehicle to observe brake warning light and apply brake pedal. Raise and support vehicle and connect a bleed hose to one of the rear wheel cylinders. Submerge other end of hose into a container partially filled with brake fluid. Have an assistant press and hold brake pedal all the way down while observing brake warning light. If warning light glows, switch is operating properly.
2. If warning light fails to glow, check circuit fuse, bulb and wiring. Repair as necessary. Repeat step 1). If warning light fails to glow, check brakelight, parking brake switches and related wiring. Repair as necessary. Repeat step 1). If warning light fails to glow, pressure differential switch is faulty. Replace combination valve assembly, bleed brake system and verify proper valve operation.

Scheme 1

Scheme 2

Scheme 3

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Scheme 5

Scheme 6

1. Raise and support vehicle. Remove wheels. Remove support key retaining screw. (Scheme 6) Using drift punch, drive out support key and spring. Remove caliper from adapter and pry outer pad from caliper.
2. Hang caliper with wire. DO NOT allow caliper to hang by brake hose. Remove inner pad and anti-rattle spring from adapter. Note position of anti-rattle spring for installation. If pads are to be reused, mark pads for installation to original position.
3. Replace pads if lining is worn to within 1/16" (1.6 mm) of rivet heads. Inspect rotor. See inspection procedure for «ROTOR»(ref-44030-S00975683222001011500000). Check piston seal for leaks and piston boot for cuts. If piston seal leaks or if boot is damaged, overhaul caliper assembly. Disconnect and plug hydraulic brake hose at caliper

Inspection

1. Raise and support vehicle. Remove wheels. On Caravan, Dakota 4WD, Town & Country and Voyager, install and torque wheel lug nuts to secure rotor. On Dakota 2WD, Pickup, Ramcharger and RWD Van, remove dust cap and temporarily adjust wheel bearings to zero end play.
2. On all models, mount dial indicator on steering arm, with plunger contacting rotor approximately 1" (25 mm) from edge of rotor. Slowly rotate rotor and note lateral runout. Lateral runout on either side of rotor should not exceed specification. Refer to the appropriate «DISC BRAKE SPECIFICATIONS»(ref-44030-S34657418822001011500000) table.
3. On Caravan, Dakota, Town & Country and Voyager, if runout exceeds specification, check runout of hub face. Before removing rotor, make a chalk mark across rotor and one wheel stud. Make mark on high side of runout.
4. Remove rotor from hub. Install dial indicator on steering arm, with stem contacting hub face near outer diameter. Place dial indicator stem outside stud circle but inside chamfer on hub rim. If runout is not within specification, hub must be replaced.
5. If hub runout is within specification, install rotor on hub with chalk marks 180 degrees apart. Install wheel lug nuts and recheck rotor runout. If runout is not within specification, resurface or replace rotor.
6. On all models, measure rotor parallelism. To measure parallelism, measure rotor thickness with micrometer at 12 equal points around rotor radius approximately 1" (25 mm) from edge of rotor. If thickness varies more than parallelism specification, resurface or replace rotor.