Engine Cooling System Chevrolet Chevy Express H2500

Fastener Tightening Specifications

Fastener Tightening Specifications

Diagnostic Starting Point - Engine Cooling

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 - Engine Cooling in order to identify the correct procedure for diagnosing the system and where the procedure is located.

Test Description

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

1. 2. Lack of communication may be due to a partial malfunction of the Class 2 serial data circuit or due to a total malfunction of the Class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 3. Determine if the Powertrain Control Module has set DTCs which may affect Engine Cooling operation are present.
3. 4. The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

Scheme 1

Scheme 2

Scan Tool Data Definitions

ECT Sensor- Range: -40°C to 150°C (-40°F to 302°F): The PCM applies 5.0 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as the engine temperature changes. When the sensor is cold (internal resistance high), the PCM senses a high signal voltage and interprets the voltage as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.

Scheme 3

Circuit Description

The PCM uses the ECT sensor to monitor the engine for an over temperature condition. This condition occurs when the coolant temperature is above 131°C (268°F). When an over temperature condition is present, DTC P1258 will set. The PCM will disable two groups of four cylinders by turning OFF the fuel injectors. By switching between the two groups of cylinders, the PCM is able to reduce the temperature of the coolant.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The PCM detects an engine over temperature condition.

Action Taken When the DTC Sets

1. The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed.
2. The PCM will turn ON the Service Engine Soon indicator.
3. The PCM will alternately disable 2 groups of four cylinders by turning OFF the fuel injectors.
4. The PCM will store conditions which were present when the DTC set as Freeze Frame and File Records data.

Conditions for Clearing the MIL/DTC

1. The PCM will turn the MIL OFF after 3 consecutive trips that the diagnostic has been run and passed.
2. The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
3. The DTC can be cleared by using the scan tool Clear DTC Information function.

Scheme 4

Symptoms - Engine Cooling

Important: Review the system operation in order to familiarize yourself with the system functions. Refer to Cooling System Description and Operation .

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to Checking Aftermarket Accessories in Wiring Systems .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Inspect the coolant recovery reservoir for the proper coolant level.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to INTERMITTENT OR POOR CONNECTIONS .

Symptom List

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

1. «Engine Overheating»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__engine-overheating)
2. «Loss of Coolant»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system)
3. «Thermostat Diagnosis»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__thermostat-diagnosis)
4. «Coolant Heater Inoperative»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system)
5. «Engine Fails To Reach Normal Operating Temperature»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system)
6. «Fan Clutch Diagnosis»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system)

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Thermostat Diagnosis

Tools Required

J 24731 Tempil Stick

Use one of the following procedures in testing for a malfunctioning thermostat.

Thermostat Test Procedure Using Tempil Sticks

The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature. Temperature sticks can be used to determine a thermostat's operating range, by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing.

1. Use a tempil stick in order to find the opening and the closing temperatures of the coolant thermostat. J 24731 -188 tempil stick melts at 87°C (188°F). The thermostat should begin to open. J 24731 -206 tempil stick melts at 97°C (206°F). The thermostat should be fully open.
2. Replace the coolant thermostat if it does not operate properly between this temperature range.

Thermostat Test Procedure Using Glycol

Inspect the operation of the thermostat by hanging the thermostat on a hook in a 50/50 percent solution of DEX-COOL® and clean drinkable water.

In order to inspect if the thermostat valve is opening properly, perform the following test

1. Completely submerge the thermostat in the glycol solution. The solution should be 11°C (22°F) above the temperature indicated on the thermostat valve.
2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should open.

In order to inspect if the thermostat valve is closing properly, perform the following test

1. Completely submerge the thermostat in a glycol solution. The solution should be 6°C (10°F) below the temperature indicated on the thermostat valve.
2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should close completely.

Scheme 9

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Scheme 11

Pressure Cap Testing

Tools Required

J 24460-01 Cooling System Pressure Tester

Scheme 12

1. Remove the pressure cap.
2. Wash the pressure cap sealing surface with water.
3. Use the J 24460-01 in order to test the pressure cap.
4. Test the pressure cap for the following conditions: Pressure release when the J 24460-01 exceeds the pressure rating of the pressure cap. Maintain the rated pressure for at least 10 seconds. Note the rate of pressure loss.
5. Replace the pressure cap under the following conditions: The pressure cap does not release pressure which exceeds the rated pressure of the cap. The pressure cap does not hold the rated pressure.

Cooling System Leak Testing

Tools Required

J 24460-01 Cooling System Pressure Tester

Scheme 13

1. Remove the pressure cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__pressure-cap-testing) .
3. Wash the pressure cap mating surface with water.
4. Use the J 24460-01 in order to apply pressure to the cooling system. Do not exceed the pressure cap rating.
5. The cooling system should hold the rated pressure for at least 2 minutes. Observe the gauge for any pressure loss.
6. Repair any leaks as required.

Noise

Fan noise is sometimes evident when the following normal conditions exist

1. The clutch is engaged for maximum cooling.
2. The engine has been running for 15-60 seconds after start-up. After this time, the clutch can redistribute the silicone fluid back to the normal disengaged operating conditions.

Fan noise or an excessive roar may occur when the following conditions exist

1. The engine speed is 2,500 RPM or higher.
2. The clutch assembly is locked up due to an internal failure.

Rotate the fan (1).

With the engine off, replace the clutch (2) if the following conditions exist

1. The fan cannot be rotated by hand.
2. The fan produces a rough, grating feel as it turns. Refer to «Fan Clutch Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__fan-clutch-replacement) .

Scheme 14

Looseness

If the fan assembly is loose, inspect the fan assembly for wear. Replace the fan assembly as necessary.

Observe the tip of the fan blade for lateral movement. Lateral movement occurs under various temperature conditions. A lateral movement measuring 6.5 mm (1/4 in) is normal. This amount of movement is not cause for replacement of the assembly.

Silicone Fluid Leaks

Small fluid leaks that are present around the bearing assembly do not affect the fan clutch operation. If leakage appears extensive, replace the fan clutch. Refer to Fan Clutch Replacement .

Engine Overheating

Use the following procedure in order to diagnose the causes of engine overheating

1. Ensure that the engine is cool. This will allow complete disengagement of the fan clutch. Important: Testing the fan clutch by rotating the fan in a repeated clockwise/counterclockwise motion causes the clutch to free-wheel. Free-wheeling is a normal result of rotating the fan in this manner. Conduct further tests in order to determine if it is necessary to replace the fan clutch.
2. Spin the fan and clutch assembly by hand. If the fan and clutch assembly easily revolves more than 5 times with no drag, replace the fan clutch.
3. If the fan clutch performs correctly but exhibits drag, position a thermometer between the fan blades and the radiator. Use any of the following methods in order to position the thermometer: Insert the thermometer sensor through one of the existing holes in the fan shroud. Place the thermometer between the radiator and the shroud. On models that do not have holes in the fan shroud, drill a 5 mm (3/16 in) hole in the fan shroud. Insert the thermometer in the hole.
4. Cover the radiator in order to induce a high engine temperature.
5. Start the engine.
6. Turn on the air conditioning.
7. Operate the engine at 2,000 RPM.
8. Wait for 5 to 10 minutes while the temperature increases sufficiently to allow the fan clutch to engage. The following conditions indicate that the fan clutch has engaged: A roaring noise or an increase in fan noise occurs. The thermometer reading drops approximately 3-10°C (5-15°F). Important: Do not continue the test past a thermometer reading of 88°C (190°F). Continuing the test past a thermometer reading of 88°C (190°F) may cause engine overheating.
9. Observe the thermometer reading when the fan clutch engages. The following conditions are cause for replacement of the fan clutch: The fan clutch does not engage while the temperature measures 65-90°C (150-195°F). If the fan clutch does not engage while the temperature is within this range, verify that the fan clutch was disengaged at the beginning of the test. Both of the following conditions exist: No temperature drop occurs The fan noise level is constant from the beginning of the test until the time when the engine temperature reaches 88°C (190°F). Do not continue the test past a thermometer reading of 88°C (190°F) in order to prevent overheating.
10. Perform the following steps as soon as the fan clutch engages: Remove the radiator cover. Turn OFF the air conditioning. Operate the engine at approximately 1,500 RPM until the coolant returns to the normal operating temperature.
11. Observe the operation of the fan clutch. The fan clutch should disengage after several minutes. Disengagement of the fan clutch is indicated by a decrease in fan noise or roar. If the fan clutch does not disengage after several minutes, the fan clutch should be replaced.

Draining Procedure

Tools Required

1. J 26568 Coolant and Battery Tester
2. J 38185 Hose Clamp Pliers

Important: Draining the cooling system with the pressure cap installed will siphon the coolant from the overflow tank.

1. Raise and support the vehicle.
2. Place a drain pan under the lower radiator hose.
3. Using the J 38185 , reposition the lower radiator hose clamp.
4. Remove the lower radiator hose from the radiator.
5. Drain the cooling system.
6. Remove the coolant pressure cap.
7. If a complete engine block drain is required, remove the engine block drain plug.
8. Inspect the coolant.
9. Follow the appropriate procedure based on the condition of the coolant. Normal in appearance - follow the filling procedure. Discolored - follow the flush procedure. Refer to «Flushing»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__flushing) .

Scheme 15

1. Install the lower radiator hose to the radiator.
2. Using the J 38185 , reposition the lower radiator hose clamp. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
3. If the engine block drain plug was removed, perform the following: Apply pipe sealer to the drain plug. Install the drain plug. Tighten Tighten the drain plug to 22 N.m (16 ft lbs).
4. Lower the vehicle.
5. Using the J 38185 , reposition the upper radiator hose clamp at the radiator.
6. Remove the upper radiator hose from the radiator.
7. Remove the air bleed hose from the radiator.
8. Place a funnel into the upper radiator hose. Important: Use a 50/50 mixture of DEX-COOL antifreeze and clean, drinkable water.
9. Slowly fill the cooling system through the upper hose with a 50/50 coolant mixture until the coolant comes out of the coolant air bleed hose.
10. Connect the upper radiator hose to the radiator.
11. Using the J 38185 , position the hose clamp into the original position on the hose.
12. Connect the coolant air bleed hose at the radiator.
13. Fill the radiator with coolant through the filler neck.
14. Rinse away any excess coolant from the engine and the engine compartment.

Flushing

Important

1. Do not use a chemical flush.
2. Store used coolant in the proper manner, such as in a used engine coolant holding tank. Do not pour used coolant down a drain. Ethylene glycol antifreeze is a very toxic chemical. Do not dispose of coolant into the sewer system or ground water. This is illegal and ecologically unsound.
3. Various methods and equipment can be used to flush the cooling system. If special equipment is used - such as a back flusher - follow the manufacturer's instructions. However, always remove the thermostat before back flushing the system.

1. Block the drive wheels.
2. Place the transmission in park (P) or neutral (N).
3. Engage the park brake.
4. Run the engine until the thermostat opens.
5. Stop the engine.
6. Follow the drain and fill procedure using only clean drinkable water. Repeat the procedure if necessary, until the fluid is nearly colorless. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
7. Fill the coolant surge tank to the FULL HOT mark. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Radiator Cleaning

An engine will overheat if the radiator has any of the following conditions

1. Leaks
2. Dirt or obstructions in the core

Use a soft bristle brush and clean hot water or a mild detergent solution in order to clean the outside of the radiator core. A car wash or dishwashing liquid is a suitable detergent.

A common city water hose may also be used in order to clean the outside of the radiator. Remove the nozzle from the hose prior to use in order to prevent damage to the fins.

Use one of the following solutions in order to pressure flush and clean the inside of the core tubes

1. Clean hot water
2. Mild car wash
3. Dishwashing liquid

Use the following steps in order to test the radiator for restrictions

1. Warm the engine.
2. Turn off the engine.
3. Feel the radiator. The radiator should be hot along the left side and warm along the right side. There should be an even temperature rise from right to left. Cold spots in the radiator indicate clogged sections. Refer to «Cooling System Description and Operation»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) for a radiator diagram.

Removal Procedure

1. Partially drain the coolant. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Disconnect the hose from the coolant recovery reservoir.
3. Remove the coolant recovery reservoir retaining screws.
4. Remove the coolant recovery reservoir.

Installation Procedure

1. Install the coolant recovery reservoir. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems
2. Install the coolant recovery reservoir retaining screws. Tighten Tighten the screws to 6 N.m (53 in lbs).
3. Connect the hose to the coolant recovery reservoir.
4. Add coolant to reservoir. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Radiator Hose Replacement - Inlet

Tools Required

J 38185 Hose Pliers

1. Partially drain the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Reposition the clamp at the radiator inlet using the J 38185 .
3. Reposition the clamp at the thermostat housing using the J 38185 .
4. Remove the radiator inlet hose from the radiator.
5. Remove the radiator inlet hose from the thermostat housing.
6. Remove the radiator inlet hose (5).

Scheme 16

1. Install the radiator inlet hose (5).
2. Install the radiator inlet hose to the radiator.
3. Install the radiator inlet hose to the thermostat housing.
4. Position the hose clamp at the thermostat housing using the J 38185 .
5. Position the hose clamp at the radiator inlet housing using the J 38185 .
6. Fill the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Radiator Hose Replacement - Outlet

Tools Required

J 38185 Hose Pliers

Scheme 17

1. Drain the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Remove the clamp at the radiator outlet using the J 38185 .
3. Remove the radiator outlet hose clamp at the engine using the J 38185 .
4. Remove the radiator outlet hose clamp at the coolant recovery reservoir using the J 38185 .
5. Remove the radiator outlet hose from the coolant recovery reservoir.
6. Remove the radiator outlet hose from the radiator.
7. Remove the radiator outlet hose from the engine.
8. Remove the radiator outlet hose (4).

1. Install the radiator outlet hose (4).
2. Install the radiator outlet hose to the engine.
3. Install the radiator outlet hose to the radiator.
4. Install the radiator outlet hose to the coolant recovery reservoir.
5. Install the radiator outlet hose clamp to the coolant recovery reservoir using the J 38185 .
6. Install the radiator outlet hose clamp to the engine using the J 38185 .
7. Install the radiator outlet clamp to the radiator outlet using the J 38185 .
8. Fill the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Scheme 18

Scheme 19

1. Disengage the plastic caps from the quick connect fittings. Pull the caps back along the pipe.
2. Using a bent-tip screwdriver or equivalent, pull on one of the open ends of the retaining ring in order to rotate the retaining ring.
3. Rotate the retaining ring around the quick connector until the retaining ring is out of position and can be completely removed. Discard the retaining rings.
4. Remove the engine oil cooler line from the quick connector fitting at the radiator. Pull the lines straight out from the connectors.
5. Clean all of the components in a suitable solvent, and dry them with compressed air.
6. Inspect the fittings, the connectors, the cooler lines, and the cooler for damage, distortion, or restriction. Replace parts as necessary.

Important: When performing the following procedure, do not reuse the old retaining rings. Replace the old retaining rings with new ones.

Do not install the new retaining ring onto the fitting by pushing the retaining ring down over the fitting.

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Scheme 26

1. Install a new retaining ring into each quick connector fitting.
2. Hook one of the open ends of the retaining ring in one of the slots in the quick connector.
3. Rotate the retaining ring around the connector until the retaining ring is positioned with all 3 ears through the 3 slots.
4. Ensure the 3 retaining ring ears can be seen from the inside of the connector and the retaining ring can move freely in the slots.
5. Install the engine oil cooler line into the quick connector fitting until a click is heard or felt. Pull back on the engine oil cooler lines to ensure a proper connection. Important: Do not manually depress the retaining clip when installing the plastic cap.
6. Snap the plastic cap onto the quick connect fitting.
7. Ensure that the plastic cap is fully seated against the fitting.
8. Ensure that no gap is present between the cap and the fitting.
9. Inspect and fill the engine oil to the proper level.

The optional oil cooler is either an integral part of the radiator or a separate unit placed in front of the radiator. The cooler lines and hoses are serviceable.

Scheme 27

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Scheme 31

1. Disconnect the cooler lines. Refer to «Engine Oil Cooler Pipe/Hose Quick Connect Fitting»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. If equipped with a 6.0L engine, perform the following: Open the oil cooler hose clip located on the lower fan shroud. Remove the oil cooler hoses from the clip. Gently, pull the oil cooler pipe fittings straight out from the radiator quick connect fittings. Raise and suitably support the vehicle.
3. If equipped with a 8.1L engine, perform the following: Remove the oil cooler hoses from the clip. Gently, pull the oil cooler pipe fittings straight out from the radiator quick connect fittings. Raise and suitably support the vehicle.
4. If equipped, remove the engine shield bolts.
5. Remove the engine shield.
6. If equipped with the a 6.0L engine, perform the following: Remove the oil cooler hose bracket bolt (1). Remove the oil cooler hose adapter bolts (2). Remove the oil cooler hose assembly and gasket. Discard the gasket. Inspect the fittings, connectors and cooler hoses for damage or distortion.
7. If equipped with a 8.1L engine, perform the following: Remove the oil cooler hose bracket bolt. Disconnect the quick connect fittings (1) at the engine. Remove the oil cooler hose assembly. Discard the gasket. Inspect the fittings, connectors and cooler hoses for damage or distortion.

Important: A distinct snap should be heard when assembling tube ends of the hose assembly to quick connectors. To ensure tube is fully inserted into the connector, check by giving tube a forceful pull.

Scheme 32

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Scheme 35

1. If equipped with a 6.0L engine, perform the following: Install the oil cooler hose assembly and a new gasket. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems. Install the oil cooler hose adapter bolts (2). Tighten Tighten the bolts to 12 N.m (106 in lbs). Install the oil cooler hose bracket bolt (1). Tighten Tighten the bolt to 25 N.m (18 ft lbs).
2. If equipped, install the engine shield.
3. Install the engine shield bolts. Tighten Tighten the bolts to 20 N.m (15 ft lbs).
4. If equipped with a 6.0L engine, perform the following: Install the oil cooler hoses to the hose clip on the fan shroud. Snap the oil cooler hose clip shut. Important: Ensure the oil cooler line being installed has a plastic cap on the end that connects to the quick connect fitting. If no plastic cap exists, or the plastic cap is damaged, obtain a new cap. Install the cap on to the cooler line prior to cooler line installation. Do not use the plastic cap in order to install the cooler line into the fitting. Connect the oil cooler lines. Refer to «Engine Oil Cooler Pipe/Hose Quick Connect Fitting»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
5. If equipped with a 8.1L engine, perform the following: Install the oil cooler hoses to the clip. Install the oil cooler lines to the radiator. Refer to «Engine Oil Cooler Pipe/Hose Quick Connect Fitting»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) . Insert the cooler line end into the quick connect fitting until a click is either heard or felt. Pull back sharply on the cooler line in order to ensure that the cooler line is installed in the quick connect fitting.

Scheme 36

Scheme 37

1. Open the hood.
2. Disconnect the oil cooler lines from the auxiliary oil cooler. Refer to «Engine Oil Cooler Pipe/Hose Quick Connect Fitting»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
3. Remove the auxiliary oil cooler from the vehicle.

Scheme 38

Scheme 39

1. Install the auxiliary oil cooler.
2. Connect the oil cooler lines to the vehicle. Refer to «Engine Oil Cooler Pipe/Hose Quick Connect Fitting»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
3. Lower the vehicle.

Fan Replacement

Tools Required

1. J 38425 Fan Hub Wrench
2. J 38426 Pulley Strap Wrench

1. If a fan assembly fails, inspect the hub and the drive components. A fan assembly may fail due to an imbalance in the hub. This type of failure may not be the fault of the blades.
2. Remove the upper fan shroud. Refer to «Fan Shroud Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
3. Insert the J 38426 around the pulley in order to secure the pulley. Insert the J 38425 onto the fan clutch nut.
4. Remove the following components: The fan (1) The fan clutch (2)
5. Inspect the following components for cracks, distortion, or other damage: The belts The hub The adapter The pulley
6. Replace the components, as necessary.

Scheme 40

1. Install the following components: The fan (1) The fan clutch (2) Tighten Tighten the fan clutch nut to 145 N.m (107 ft lbs).
2. Install the upper fan shroud. Refer to «Fan Shroud Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Fan Clutch Replacement

Tools Required

1. J 38425 Fan Hub Wrench
2. J 41240 Fan Clutch Remover and Installer

1. Remove the fan shroud bolts (1) from the top of the radiator support.
2. Remove the fan shroud bolts (3) from the sides of the fan shroud.
3. Remove the upper fan shroud (2).
4. Install the J 38425 onto the fan clutch nut. Install the J 41240 in order to secure the pulley.
5. Remove the fan clutch assembly.
6. Inspect the following components for cracks, distortion, or other damage: The belt The hub The adapter The pulley
7. Remove the bolts from the fan clutch.
8. Separate the fan clutch from the fan blade.

1. Install the fan clutch to the fan blade. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the bolts to the fan clutch. Tighten Tighten the bolts to 25 N.m (18 ft lbs).
3. Install the fan clutch assembly to the pulley.
4. Install the J 38425 onto the fan clutch nut. Install the J 41240 in order to secure the pulley. Tighten Tighten the nut to 95 N.m (70 ft lbs).
5. Install the upper fan shroud (2).
6. Install the fan shroud bolts (1) to the top of the radiator support. Tighten Tighten the bolts to 6 N.m (53 in lbs).
7. Install the fan shroud bolts (3) to the sides of the fan shroud. Tighten Tighten the bolts to 6 N.m (53 in lbs).

Important: The thermostat is not serviceable separately. The water pump inlet and thermostat must be replaced as an assembly.

Scheme 41

1. Remove the bolt from the coolant recovery reservoir and reposition.
2. Remove air cleaner assembly.
3. Remove the radiator outlet hose. Refer to «Radiator Hose Replacement - Outlet»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__radiator-hose-replacement-outlet) .
4. Remove the water pump inlet bolts.
5. Remove the water pump inlet and thermostat from the water pump.

Scheme 42

1. Install the thermostat and water pump inlet to the water pump. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the water pump inlet bolts. Tighten Tighten the water pump inlet bolts to 15 N.m (11 ft lbs).
3. Install the radiator outlet hose. Refer to «Radiator Hose Replacement - Outlet»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__radiator-hose-replacement-outlet) .
4. Install the air cleaner assembly.
5. Install the coolant recovery reservoir and bolt. Tighten Tighten the bolt to 11 N.m (97 in lbs).

Scheme 43

Scheme 44

1. Remove the air cleaner and the duct assembly.
2. Partially drain the coolant. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
3. Remove the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
4. Disconnect the radiator hose from the thermostat housing.
5. Remove the bolts attaching the thermostat housing to the thermostat.
6. Remove the thermostat housing.
7. Remove the thermostat.
8. Clean the gasket mating surfaces.

Scheme 45

Scheme 46

1. Install the thermostat.
2. Install the thermostat housing to the intake manifold. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
3. Install the bolts to the housing. Tighten Tighten the bolts to 25 N.m (18 ft lbs).
4. Connect the radiator hose to the thermostat housing.
5. Install the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
6. Install the air cleaner and the duct.
7. Refill the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
8. Bleed the air from the cooling system.
9. Inspect the thermostat housing and the gasket for coolant leaks.

Scheme 47

Scheme 48

Scheme 49

Scheme 50

1. Remove the intake manifold. Refer to «INTAKE MANIFOLD REPLACEMENT»(/chevrolet/chevy-express-h2500/2003-2003/remont/mechanical/#engine-mechanical-48l-53l-60l) .
2. Remove the coolant air bleed pipe studs (1).
3. Remove the coolant air bleed pipe (2) with gaskets (3).
4. Remove the coolant air bleed pipe cover bolts (1) and covers (2).
5. Remove the gaskets from the coolant air bleed pipe and covers.
6. Discard the gaskets.
7. Remove the coolant air bleed hose (1) from the pipe (2).

Scheme 51

Scheme 52

Scheme 53

Scheme 54

1. Install the coolant air bleed hose (1) onto the pipe (2). Important: Install the gaskets properly onto the pipe and covers. Position the O-ring seal onto the nipple portion of the pipe.
2. Install the gaskets onto the coolant air bleed pipe and covers.
3. Install the coolant air bleed pipe (2) and gaskets (3) onto the cylinder heads. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
4. Install the coolant air bleed pipe studs (1). Tighten Tighten the coolant air bleed pipe studs to 12 N.m (106 in lbs).
5. Install the coolant air bleed pipe covers (2) and bolts (1). Tighten Tighten the coolant air bleed pipe cover bolts to 12 N.m (106 in lbs).
6. Install the intake manifold. Refer to «INTAKE MANIFOLD REPLACEMENT»(/chevrolet/chevy-express-h2500/2003-2003/remont/mechanical/#engine-mechanical-48l-53l-60l) .

Scheme 55

Scheme 56

1. Remove the air cleaner assembly.
2. Remove the generator. Refer to «GENERATOR»(/chevrolet/chevy-express-h2500/2003-2003/remont/charging-system/#charging-system) .
3. Partially drain the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
4. Reposition the coolant air bleed hose clamp at the throttle body.
5. Remove the coolant air bleed hose from the throttle body.
6. Reposition the coolant air bleed hose clamp at the pipe.
7. Remove the coolant air bleed hose (1) from the pipe (2).

Scheme 57

Scheme 58

1. Install the coolant air bleed hose (1) to the pipe (2).
2. Position the coolant air bleed hose clamp at the pipe.
3. Install the coolant air bleed hose to the throttle body.
4. Position the coolant air bleed hose clamp at the throttle body.
5. Install the generator. Refer to «GENERATOR»(/chevrolet/chevy-express-h2500/2003-2003/remont/charging-system/#charging-system) .
6. Install the air cleaner assembly.
7. Fill the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Water Pump Replacement (4.3L Engine)

Tools Required

J 41240 Fan Clutch Remover and Installer

Scheme 59

Scheme 60

Scheme 61

Scheme 62

1. Remove the air cleaner assembly.
2. Remove the air cleaner outlet resonator duct.
3. Drain the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
4. Remove the cooling fan. Refer to «Fan Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__fan-replacement) .
5. Remove the drive belt. Refer to «DRIVE BELT REPLACEMENT»(/chevrolet/chevy-express-h2500/2003-2003/remont/mechanical/#engine-mechanical-43l) .
6. Reposition the radiator outlet hose clamps at the surge tank and water pump.
7. Remove the radiator outlet hose from the surge tank.
8. Remove the radiator outlet hose from the water pump.
9. Reposition the water pump inlet hose clamps.
10. Remove the water pump inlet hose.
11. Using J 41240 to hold the water pump pulley, remove the water pump pulley bolts.
12. Remove the water pump bolts.
13. Remove the water pump.
14. Remove and discard the water pump gaskets.
15. Clean and inspect the water pump, if necessary. Refer to «WATER PUMP CLEANING AND INSPECTION»(/chevrolet/chevy-express-h2500/2003-2003/remont/mechanical/#engine-mechanical-43l__water-pump-cleaning-and-inspection) .

Scheme 63

Scheme 64

Scheme 65

Scheme 66

1. If reusing the fasteners, apply sealant GM P/N 12346004 (Canadian P/N 10953480), or equivalent to the threads of the water pump bolts.
2. Install NEW water pump gaskets and the water pump. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
3. Install the water pump bolts. Tighten Tighten the water pump bolts to 45 N.m (33 ft lbs).
4. Using J 41240 to hold the water pump pulley, install the water pump pulley bolts. Tighten Tighten the water pump pulley bolts to 25 N.m (18 ft lbs). Important: After assembly, the hose clamp tangs (water pump end) must point forward and the upper tang should be level with the outside diameter of the water pump inlet hose.
5. Install the water pump inlet hose.
6. Position the water pump inlet hose clamps.
7. Install the radiator outlet hose to the water pump.
8. Install the radiator outlet hose to the surge tank.
9. Position the radiator outlet hose clamps at the surge tank and water pump.
10. Install the drive belt. Refer to «DRIVE BELT REPLACEMENT»(/chevrolet/chevy-express-h2500/2003-2003/remont/mechanical/#engine-mechanical-43l) .
11. Install the cooling fan. Refer to «Fan Clutch Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__fan-clutch-replacement) .
12. Install the air cleaner outlet resonator duct.
13. Install the air cleaner assembly.
14. Fill the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
15. Inspect the cooling system for leaks.

Scheme 67

Scheme 68

Scheme 69

Scheme 70

1. Drain the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Remove the air cleaner assembly.
3. Remove the fan blade. Refer to «Fan Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__fan-replacement) .
4. Reposition the inlet hose clamp at the water pump.
5. Remove the inlet hose from the water pump.
6. Reposition the outlet hose clamp at the water pump.
7. Remove the outlet hose from the water pump.
8. Reposition the heater inlet hose clamp at the water pump.
9. Remove the heater inlet hose from the water pump.
10. Remove the accessory drive belt tensioner bolts and tensioner from the engine.
11. Remove the water pump bolts.
12. Remove the water pump and gaskets.
13. Discard the water pump gaskets.

Important: All gaskets surfaces are to be free of oil or other foreign material during assembly.

Scheme 71

Scheme 72

Scheme 73

Scheme 74

1. Install the water pump and NEW gaskets. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the water pump bolts. Tighten Tighten the water pump bolts a first pass to 15 N.m (11 ft lbs). Tighten the water pump bolts a final pass to 30 N.m (22 ft lbs).
3. Install the heater inlet hose to the water pump.
4. Position the heater inlet hose clamp at the water pump.
5. Install the outlet hose to the water pump.
6. Position the outlet hose clamp at the water pump.
7. Install the inlet hose to the water pump.
8. Position the inlet hose clamp at the water pump.
9. Install the accessory drive belt tensioner and bolts to the engine. Tighten Tighten the bolts to 50 N.m (37 ft lbs).
10. Install the accessory drive belt. Refer to «DRIVE BELT REPLACEMENT - ACCESSORY»(/chevrolet/chevy-express-h2500/2003-2003/remont/mechanical/#engine-mechanical-48l-53l-60l) .
11. Install the fan blade. Refer to «Fan Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system__fan-replacement) .
12. Install the air cleaner assembly.
13. Fill the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Scheme 75

1. Remove the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Remove the fan shroud bolts (1,3,4).
3. Remove the fan shroud (2,5).

Scheme 76

1. Install the fan shroud (2,5). CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the fan shroud bolts (1,3,4). Tighten Tighten the bolts to 6 N.m (53 in lbs).
3. Install the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Scheme 77

1. Remove the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Remove the fan shroud bolts (1,3,4).
3. Remove the fan shroud (2,5).

Scheme 78

1. Install the fan shroud (2,5). CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the fan shroud bolts (1,3,4). Tighten Tighten the bolts to 6 N.m (53 in lbs).
3. Install the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Scheme 79

1. Remove the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Remove the fan shroud bolts (1,3,4).
3. Remove the fan shroud (2,5).

Scheme 80

1. Install the fan shroud (2,5). CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the fan shroud bolts (1,3,4). Tighten Tighten the bolts to 6 N.m (53 in lbs).
3. Install the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) . .

Radiator Replacement

Tools Required

J 38185 Hose Clamp Pliers

Important: Always install a new set of insulators when replacing a radiator. Used insulators may be worn or too large for the new radiator. These conditions may cause the New radiator to be loose.

Scheme 81

Scheme 82

Scheme 83

1. Remove the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Remove the clamp at the radiator inlet using the J 38185 .
3. Remove the radiator inlet hose (5) from the radiator.
4. Remove the clamp at the radiator outlet using the J 38185 .
5. Remove the radiator outlet hose (4) from the radiator.
6. Remove the outlet heater hose clamp at the radiator using the J 38185 .
7. Remove the outlet heater hose (2) from the radiator.
8. Remove the automatic transmission cooler lines. Refer to «OIL COOLER LINES»(/chevrolet/chevy-express-h2500/2003-2003/remont/automatic-trans/#automatic-transmission-servicing-4l60-e) for 4L60-E or «OIL COOLER LINES»(/chevrolet/chevy-express-h2500/2003-2003/remont/automatic-trans/#automatic-transmission-servicing-4l80-e) for 4L80-E.
9. Remove the engine oil cooler lines. Refer to «Engine Oil Cooler Pipe/Hose Quick Connect Fitting»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
10. Remove the fan shroud bolts (1) from the top of the radiator support.
11. Remove the fan shroud bolts (3) from the sides of the fan shroud.
12. Remove the radiator (2).
13. Remove the radiator insulators (1,3).
14. Inspect the following components: The radiator The insulators The hoses and clamps The mounting hardware Replace the components as necessary.

Scheme 84

Scheme 85

Scheme 86

1. Install the radiator insulators (1,3).
2. Install the radiator (2). CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
3. Install the fan shroud bolts (1) to the top of the radiator support. Tighten Tighten the bolts to 6 N.m (53 in lbs).
4. Install the fan shroud bolts (3) to the sides of the fan shroud. Tighten Tighten the bolts to 6 N.m (53 in lbs).
5. Install the engine oil cooler lines. Refer to «Engine Oil Cooler Pipe/Hose Quick Connect Fitting»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
6. Install the automatic transmission oil cooler lines. Refer to «OIL COOLER LINES»(/chevrolet/chevy-express-h2500/2003-2003/remont/automatic-trans/#automatic-transmission-servicing-4l60-e) for 4L60-E or «OIL COOLER LINES»(/chevrolet/chevy-express-h2500/2003-2003/remont/automatic-trans/#automatic-transmission-servicing-4l80-e) for 4L80-E.
7. Install the radiator outlet hose (4) to the radiator.
8. Install the radiator outlet clamp to the radiator outlet using the J 38185 .
9. Install the radiator inlet hose (5) to the radiator.
10. Install the hose clamp at the radiator inlet housing using the J 38185 .
11. Install the outlet heater hose (2).
12. Install the outlet heater hose clamp using the J 39529 .
13. Install the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
14. Inspect the automatic transmission fluid level.
15. Inspect the engine oil level.

Scheme 87

1. Drain the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Disconnect the heater cord from the coolant heater (4).
3. Loosen the coolant heater bolt.
4. Remove the coolant heater from the engine block.
5. Do not score the machined surface of the hole.
6. Grasp the plug with pliers.
7. Pull the plug from the engine block.
8. Clean the core plug hole in order to remove the following substances: Burrs Compound Paint Rough spots

Scheme 88

Scheme 89

Scheme 90

1. Coat the O-ring seal and the cleaned surface of the plug opening with water resistant high-temperature grease lubricant GM P/N 9985164 (Canadian P/N 10953480), or the equivalent. Important: Avoid element contact with the inside walls of the engine block.
2. Tightly push the coolant heater (1) into the engine block. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
3. Tighten the coolant heater bolt until both of the locking wings draw tightly against the inner wall of the engine block. Tighten Tighten the bolt to 2 N.m (18 in lbs). CAUTION: The heater cord must not touch the engine, hot pipes, manifold, or any moving parts. Route the cord to the left front of the engine compartment securing with tie straps as necessary to prevent damage.
4. Connect the heater cord to the coolant heater (4).
5. Fill the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
6. Inspect the cooling system for leaks.

Scheme 91

Scheme 92

1. Drain the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .
2. Raise and suitably support the vehicle.
3. Disconnect the coolant heater electrical connector (2). Important: Do not score the surface of the engine block hole when removing the coolant heater.
4. Remove the coolant heater from the engine block.
5. Remove any burrs, sealer, paint or other rough spots.

Scheme 93

Scheme 94

1. If re-using the old coolant heater, apply thread sealant GM P/N 12346004 (Canadian P/N 10953480), or equivalent to the threads. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the coolant heater to the engine block. Tighten Tighten the coolant heater to 50 N.m (37 ft lbs). CAUTION: The heater cord must not touch the engine, hot pipes, manifold, or any moving parts. Route the cord to the left front of the engine compartment securing with tie straps as necessary to prevent damage.
3. Connect the coolant heater electrical connector (2).
4. Lower the vehicle.
5. Fill the cooling system. Refer to «Draining and Filling Cooling System»(/chevrolet/chevy-express-h2500/2003-2003/remont/cooling-system-mechanical/#engine-cooling-system) .

Scheme 95

Scheme 96

1. Raise and suitably support the vehicle.
2. Disconnect the coolant heater electrical connector (2).
3. Remove the coolant heater cord retainer and bolts.
4. Remove the coolant heater cord.

Scheme 97

Scheme 98

1. Install the coolant heater cord. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the coolant heater cord bolts and retainer. Tighten Tighten the coolant heater cord bolts to 8 N.m (71 in lbs).
3. Connect the coolant heater electrical connector (2).
4. Lower the vehicle.

Coolant Heater

The optional engine coolant heater (RPO KO5) is designed to warm the coolant in the engine block area for improved starting in very cold weather (temperatures below -29°C (-20°F)). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The engine coolant heater operates using AC external power and a heating element installed in the water jacket of the engine block. The heating element warms the coolant when the heater cord is plugged into an AC power source.

The unit is equipped with a detachable AC power cord. A weather shield on the cord is provided to protect the plug when not in use.

The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system is designed to remove approximately one-third of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the coolant does not flow to the radiator until the thermostat opens. This allows the engine to warm quickly.

Cooling Cycle

Coolant flows from the radiator outlet and into the water pump inlet. Some coolant flows from the water pump, to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost capability as the coolant warms up.

Coolant also flows from the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders where it absorbs heat.

The coolant then flows through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the water jackets surrounding the combustion chambers and valve seats, where it absorbs additional heat.

Some engine applications, coolant is also directed to the throttle body. There it circulates through passages in the casting. The coolant assists in regulating the throttle body temperature.

From the cylinder heads, the coolant flows to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine reaches operating temperature or it will flow through the thermostat and into the radiator where it is cooled. At this point, the coolant flow cycle is completed.

Efficient operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components

Coolant

The engine coolant is a solution made up of a 50-50 mixture of DEX-COOL and suitable drinking water. The coolant solution carries excess heat away from the engine to the radiator, where the heat is dissipated to the atmosphere.

Radiator

The radiator is a heat exchanger. It consists of a core and two tanks. The aluminum core is a tube and fin cross-flow design that extends from the inlet tank to the outlet tank. Fins are placed around the outside of the tubes to improve heat transfer to the atmosphere. The inlet and outlet tanks are a molded high temperature, nylon reinforced plastic material. A high temperature rubber gasket seals the tank flange edge to the aluminum core. The tanks are clamped to the core with clinch tabs. The tabs are part of the aluminum header at each end of the core. The radiator also has a drain cock located in the bottom of the left hand tank. The drain cock unit includes the drain cock and drain cock seal.

The radiator removes heat from the coolant passing through it. The fins on the core transfer heat from the coolant passing through the tubes. As air passes between the fins, it absorbs heat and cools the coolant.

During vehicle use, the coolant is heated and expands. The increased coolant volume flows into the surge tank. As the coolant circulates, any air is allowed to bubble out. Coolant without air bubbles absorbs heat much better than coolant with bubbles.

Coolant Recovery System

The coolant recovery system consists of a plastic coolant recovery reservoir, an overflow tube, and a pressure cap on the radiator. The recovery reservoir is also called a recovery tank or expansion tank. It is partially filled with coolant and is connected to the radiator fill neck with the overflow tube. Coolant can flow back and forth between the radiator and the reservoir.

In effect, a cooling system with a coolant recovery reservoir is a closed system. When the pressure in the cooling system gets too high, it will open the pressure valve in the pressure cap. This allows the coolant, which has expanded due to being heated, to flow through the overflow tube and into the recovery reservoir. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum opens the vacuum valve in the pressure cap, allowing some of the coolant in the reservoir to be siphoned back into the radiator. Under normal operating conditions, no coolant is lost. Although the coolant level in the recovery reservoir goes up and down, the radiator and cooling system are kept full. An advantage to using a coolant recovery reservoir is that it eliminates almost all air bubbles from the cooling system. Coolant without air bubbles absorbs heat much better than coolant with bubbles.

Pressure Cap

The pressure cap seals the cooling system. It contains a blow off or pressure relief valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring, which protects the radiator from excessive cooling system pressure. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, might cause the radiator and/or coolant hoses to collapse.

The pressure cap allows cooling system pressure to build up as the temperature increases. As the pressure builds, the boiling point of the coolant increases. Engine coolant can be safely run at a temperature much higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant is, the faster the heat transfers from the radiator to the cooler, passing air.

The pressure in the cooling system can get too high. When the cooling system pressure exceeds the rating of the pressure cap, it raises the pressure valve, venting the excess pressure.

As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the surge tank. This equalizes the pressure in the cooling system with atmospheric pressure, preventing the radiator and coolant hoses from collapsing.

Cooling Fan and Clutch

The engine cooling fan and clutch are driven by the crankshaft via the drive belt. The cooling fan draws air through the radiator to improve the transfer of heat from the coolant to the atmosphere. As the fan blades spin, they pull cool, outside air past the radiator core. The fan clutch drives the cooling fan. The fan clutch controls the amount of torque that is transmitted from the crankshaft to the fan blades. The clutch allows more torque to engage on the fan when the engine operating temperature increases and/or the vehicle speed is low. As the torque increases, the fan turns more quickly. The fan clutch decreases the torque applied to the cooling fan when the engine temperature decreases and/or the vehicle speed is high. As the torque decreases, the fan speed decreases.

Air Baffles and Seals

The cooling system uses deflectors, air baffles and air seals to increase cooling system capability. Deflectors are installed under the vehicle to redirect airflow beneath the vehicle and through the radiator to increase engine cooling. Air baffles are also used to direct airflow through the radiator and increase cooling capability. Air seals prevent air from bypassing the radiator and A/C condenser, and prevent recirculation of hot air for better hot weather cooling and A/C condenser performance.

Water Pump

The water pump is a centrifugal vane impeller type pump. The pump consists of a housing with coolant inlet and outlet passages, a retaining plate, pulley and an impeller. The impeller is mounted on the pump shaft, and consists of a series of flat or curved blades or vanes on a flat plate. When the impeller rotates, the coolant between the vanes is thrown outward by centrifugal force. The impeller shaft is supported by one or more sealed bearings. The sealed bearings never need to be lubricated. Grease cannot leak out, dirt and water cannot get in as long as the seal is not damaged or worn.

The purpose of the water pump is to circulate coolant throughout the cooling system. The water pump is driven by the crankshaft via the drive belt.

Thermostat

The thermostat is a coolant flow control component. It's purpose is to help regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a small piston. When the element is heated, it expands and exerts pressure against a small piston. This pressure forces the valve to open. As the element is cooled, it contracts. This contraction allows a spring to push the valve closed.

When the coolant temperature is below 85°C (185°F) for diesel engines and below 91°C (195°F) for gas engines, the thermostat valve remains closed. This prevents circulation of the coolant from the radiator and allows the engine to warm up. After the coolant temperature reaches 85°C (185°F) or 91°C (195°F), the thermostat valve will open. The coolant is then allowed to circulate through the thermostat to the engine and then to the radiator where the engine heat is dissipated to the atmosphere. The thermostat also provides a restriction in the cooling system, after it has opened. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block.

Engine Oil Cooler

The engine oil cooler is a heat exchanger. It is located inside the left side end tank of the radiator. The engine oil temperature is controlled by the temperature of the engine coolant that surrounds the oil cooler in the radiator.

The engine oil pump pumps the oil through the engine oil cooler line to the oil cooler. The oil then flows through the cooler where the engine coolant absorbs heat from the oil. The oil is then pumped through the oil cooler return line, to the oil filter, to the engine block oil system.

Transmission Oil Cooler

The transmission oil cooler is a heat exchanger. It is located inside the right side end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant in the radiator.

The transmission oil pump, pumps the fluid through the transmission oil cooler line to the transmission oil cooler. The fluid then flows through the cooler where the engine coolant absorbs heat from the fluid. The fluid is then pumped through the transmission oil cooler return line, to the transmission.

Scheme 99

Scheme 100

See also:
• INTERMITTENT OR POOR CONNECTIONS
• INTAKE MANIFOLD REPLACEMENT
• GENERATOR
• DRIVE BELT REPLACEMENT
• WATER PUMP CLEANING AND INSPECTION
• OIL COOLER LINES
• OIL COOLER LINES
• Symptoms - Engine Cooling
• Cooling System Description and Operation
• Engine Overheating
• Thermostat Diagnosis
• Pressure Cap Testing
• Fan Clutch Replacement
• Flushing
• Radiator Hose Replacement - Outlet
• Fan Replacement