Engine Cooling System: Diagnosis Chevrolet Silverado 1500 HD

Diagnostic Starting Point - Engine Cooling

Begin the system diagnosis with the Diagnostic System Check - Engine Cooling . The Diagnostic System Check will provide the following information

1. The identification of the control module(s) which command the system.
2. The ability of the control module(s) to communicate through the serial data circuit.
3. The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Data Definitions

Coolant Level Switch-Range: Low/OK: This parameter indicates when the engine coolant level is low. The scan tool displays Low when the PCM detects the engine coolant level switch is open.

ECT-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.

Displayed Coolant Temperature-Range: 32-127°C (89-260°F): This data is the coolant temperature the Instrument Cluster is attempting to display on the coolant temperature gauge. This data may differ from the monitored coolant temperature for a period of time due to filtering. The data may also differ from the monitored coolant temperature when coolant temperature is not in the range of 71-127°C (160-260°F) since the display is limited to these values. If a Class 2 communication failure occurs, this data will be at the minimum value of 32°C (89°F).

Monitored Coolant Temperature-Range: 40-215°C (40-419°F): This data is the clusters measurement of the engine coolant temperature as provided by the PCM on the Class 2 serial data line.

Scheme 12

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 132°C (270°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

1. DTCs P0117, P0118, P1114, and P1115 are not active.
2. The engine is running.

Conditions for Setting the DTC

The engine coolant temperature is above 132°C (270°F) for 10 seconds or more.

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 signal the IPC to turn ON the Service Engine Soon indicator.
3. The PCM will alternately disable two 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.

Scheme 13

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.

Symptoms - Engine Cooling

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to «CHECKING AFTERMARKET ACCESSORIES»(ref-189004-S21780885952005091300000) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Inspect the surge tank reservoir for the proper coolant level.

Symptom List

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

1. «Engine Overheated Indicator Always On»(ref-188992-S05329198232005091300000)
2. «Engine Coolant Temperature Indicator Always On»(ref-188992-S04304292672005091300000)
3. «Low Engine Coolant Indicator Always On»(ref-188992-S26265981152005091300000)
4. «Coolant Heater Inoperative»(ref-188992-S41431710102005091300000)
5. «Engine Overheating»(ref-188992-S42573659882005091300000)
6. «Loss of Coolant»(ref-188992-S04738320592005091300000)
7. «Thermostat Diagnosis»(ref-188992-S33467482702005091300000)
8. «Engine Fails To Reach Normal Operating Temperature»(ref-188992-S39493775482005091300000)
9. «Fan Clutch Diagnosis»(ref-188992-S38854090062005091300000)

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

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

Scheme 23

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 24

Scheme 25

Pressure Cap Testing

Scheme 26

1. Remove the pressure cap.
2. Wash the pressure cap sealing surface with water.
3. Use the J 24460-01 (1) with J 42401 (2) 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.

Inspection Procedure

1. Inspect the thermostats for sticking, cracks, and/or leakage of wax.
2. Replace the thermostats if damage is found.
3. Clean the thermostat housing and thermostat housing cover sealing surfaces.

Scheme 27

Scheme 28

1. Install the thermostats and seals to the thermostat housing. The rear thermostat (4) has 2 vent valves. Install with the vent valves towards the rear of engine.
2. Install the thermostat housing cover with a NEW gasket. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
3. Install the thermostat housing cover bolts. Tighten Tighten the bolts to 21 N.m (15 lb ft).
4. Install the fuel line bracket bolt. Tighten Tighten the bolt to 21 N.m (15 lb ft).
5. Install the water outlet. Refer to «Water Outlet Tube Replacement (6.6L Engine)»(ref-188992-S08051206432005091300000) .

Scheme 29

Scheme 30

1. Drain the cooling system. Refer to «Draining and Filling Cooling System»(ref-188992-S10584397332005091300000) .
2. Reposition the inlet hose clamp at the water outlet.
3. Remove the inlet hose from the water outlet.
4. Remove the water outlet bolts (2).
5. Remove the water outlet (1).
6. Remove the thermostat (3).

Scheme 31

Scheme 32

1. Install the thermostat (3).
2. Install the water outlet (1). NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
3. Install the water outlet bolts (2). Tighten Tighten the bolts to 30 N.m (22 lb ft).
4. Install the inlet hose to the water outlet.
5. Position the inlet hose clamp at the water outlet.
6. Fill the cooling system. Refer to «Draining and Filling Cooling System»(ref-188992-S10584397332005091300000) .

Scheme 33

Scheme 34

Scheme 35

Scheme 36

Scheme 37

Scheme 38

Scheme 39

Scheme 40

Scheme 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

1. Loosen the outlet duct clamp at the upper intake manifold cover.
2. Remove the upper intake manifold cover from the outlet duct.
3. Remove the upper intake manifold cover.
4. Drain the cooling system. Refer to «Draining and Filling Cooling System»(ref-188992-S10584397332005091300000) .
5. Disconnect the negative battery cables. Refer to «BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE (SINGLE BATTERY)»(ref-188993-S31717251372005091300000) or «BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE (AUXILIARY BATTERY)»(ref-188993-S36299735782005091300000) .
6. Remove the upper fan shroud. Refer to «Fan Shroud Replacement - Upper (W/O M74)»(ref-188992-S11141372892005091300000) or «Fan Shroud Replacement - Upper (W/M74)»(ref-188992-S15776187022005091300000) .
7. Remove the drive belt. Refer to «DRIVE BELT ROUTING»(ref-166550-S34031604972004092300000) .
8. Disconnect the air conditioning (A/C) compressor clutch electrical connector (5).
9. Disconnect the A/C cut out switch electrical connector.
10. Remove the A/C compressor bolts.
11. Move the A/C compressor with the hoses attached to the right side of the engine compartment.
12. Remove the generator positive cable to generator nut.
13. Remove the positive cable from the generator.
14. Remove the clip holding the positive cable to the engine front cover.
15. Remove the battery positive cable junction block to power steering pump bolt.
16. Move the generator positive cable and the junction block bracket aside.
17. Disconnect the generator electrical connector (1).
18. Disconnect the engine coolant temperature (ECT) sensor electrical connector.
19. Remove the power steering pump bracket and secure to the side. Do not remove the power steering pump from the bracket. The hoses and battery cables can remain on the power steering pump.
20. Remove the fuel bleed valve and positive crankcase ventilation (PCV) oil separator bracket bolt from the generator bracket.
21. Remove the heater outlet hose bracket bolt from the generator bracket.
22. Remove the ribbed idler pulley.
23. Remove the generator bracket and position to the side. The generator does not require removal. The drive belt tensioner does not require removal.
24. Remove the oil fill tube. Refer to «OIL FILLER TUBE»(ref-161511-S24483342622004041300000) .
25. Remove the water outlet. Refer to «Water Outlet Tube Replacement (6.6L Engine)»(ref-188992-S08051206432005091300000) .
26. Remove the heater inlet pipe to fuel filter bolt.
27. Remove the heater inlet pipe with O-ring seal from the crossover.
28. Remove the turbocharger coolant return pipe clamps and hose.
29. Remove the fuel line bracket from the thermostat housing crossover.
30. Remove the cooling fan pulley. Refer to «Cooling Fan Pulley Replacement (6.6L Engine)»(ref-188992-S00439847922005091300000) .
31. Remove the thermostat housing bolts and nuts from the left cylinder head.
32. Remove the thermostat housing bolts and nuts from the right cylinder head.
33. Remove the bypass pipe to water pump bolts.
34. Remove the thermostat housing with the bypass pipe.
35. Remove the bypass pipe to water pump O-ring.
36. Remove the bypass pipe from the thermostat housing.
37. Remove the O-ring from the bypass pipe.
38. Remove the thermostat cover bolts.
39. Remove the thermostat cover.
40. Remove the thermostats with seals.
41. Remove the thermostat seals.
42. If required, clean and inspect the thermostat housing.

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

Scheme 51

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Scheme 56

Scheme 57

Scheme 58

1. Install the thermostats with the seals. The thermostat with the vent valves goes toward the rear of the engine. Install with the vent valves towards the rear of the engine.
2. Install the thermostat cover and gasket. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
3. Install the thermostat cover bolts. Tighten Tighten the bolts to 21 N.m (15 lb ft).
4. Install a new O-ring to the bypass pipe. Lubricate the O-ring with coolant.
5. Install the bypass pipe to the thermostat housing crossover.
6. Install NEW thermostat housing gaskets.
7. Install a NEW O-ring for the bypass pipe to the water pump.
8. Install the thermostat housing with the bypass pipe.
9. Install the bypass pipe to water pump bolts. Tighten Tighten the bolts to 21 N.m (15 lb ft).
10. Install the thermostat housing bolts and nuts. Tighten Tighten the bolts and nuts to 21 N.m (15 lb ft).
11. Install the fuel line bracket and bolt. Tighten Tighten the bolt to 21 N.m (15 lb ft).
12. Install the turbocharger coolant return pipe hose and clamps.
13. Install the cooling fan pulley. Refer to «Cooling Fan Pulley Replacement (6.6L Engine)»(ref-188992-S00439847922005091300000) .
14. Install a NEW O-ring seal to the heater inlet pipe.
15. Install the heater inlet pipe to the thermostat housing crossover.
16. Install the heater inlet pipe to thermostat housing crossover bolt. Tighten Tighten the bolt to 21 N.m (15 lb ft).
17. Install the heater inlet pipe to fuel filter bolt. Tighten Tighten the bolt to 21 N.m (15 lb ft).
18. Install the generator bracket and bolts. Tighten Tighten the bolts to 50 N.m (37 lb ft).
19. Install the ribbed idler pulley and the bolt. Tighten Tighten the bolt to 43 N.m (32 lb ft).
20. Install the heater outlet hose bracket bolt. Tighten Tighten the bolt to 21 N.m (15 lb ft).
21. Install the fuel bleed valve and PCV oil separator bracket nuts to the generator bracket. Tighten Tighten the nuts to 25 N.m (18 lb ft).
22. Install the power steering pump bracket and bolts. Tighten Tighten the bolts to 46 N.m (34 lb ft).
23. Install the water outlet. Refer to «Water Outlet Tube Replacement (6.6L Engine)»(ref-188992-S08051206432005091300000) .
24. Position the generator positive cable.
25. Install the generator positive cable in the clip on the engine front cover.
26. Install the generator positive cable nut. Tighten Tighten the nut to 9 N.m (80 lb in).
27. Install the battery positive cable junction block bracket and bolt to the power steering pump. Tighten Tighten the bolt to 9 N.m (80 lb in).
28. Connect the ECT sensor electrical connector.
29. Connect the generator electrical connector (1).
30. Position the A/C compressor.
31. Install the A/C compressor bolts. Tighten Tighten the bolts to 50 N.m (37 lb ft).
32. Connect the A/C cut out switch electrical connector.
33. Connect the A/C compressor clutch electrical connector (5).
34. Install the drive belt. Refer to «DRIVE BELT ROUTING»(ref-166550-S34031604972004092300000) .
35. Install the upper fan shroud. Refer to «Fan Shroud Replacement - Upper (W/O M74)»(ref-188992-S11141372892005091300000) or «Fan Shroud Replacement - Upper (W/M74)»(ref-188992-S15776187022005091300000) .
36. Fill the cooling system. Refer to «Draining and Filling Cooling System»(ref-188992-S10584397332005091300000) .
37. Connect the negative battery cables. Refer to «BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE (SINGLE BATTERY)»(ref-188993-S31717251372005091300000) or «BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE (AUXILIARY BATTERY)»(ref-188993-S36299735782005091300000) .
38. Install the upper intake manifold cover.
39. Install the upper intake manifold cover to the outlet duct.
40. Tighten the outlet duct clamp at the upper intake manifold cover. Tighten Tighten the clamp to 6 N.m (53 lb in).

Scheme 59

Scheme 60

Scheme 61

Scheme 62

Scheme 63

Scheme 64

1. Drain the cooling system. Refer to «Draining and Filling Cooling System»(ref-188992-S10584397332005091300000) .
2. Remove the drive belt tensioner.
3. Reposition the inlet hose clamp at the water crossover.
4. Remove the inlet hose from the water crossover.
5. Reposition the heater inlet hose clamp at the water crossover.
6. Remove the heater inlet hose from the water crossover.
7. Reposition the bypass hose clamps at the water crossover and water pump.
8. Remove the bypass hose.
9. Remove the generator. Refer to «GENERATOR (4.3L ENGINE)»(ref-167946-S33213416432004102600000) or «GENERATOR (4.8L, 5.3L & 6.0L ENGINES)»(ref-167946-S15598882462004102600000) or «GENERATOR (6.6L ENGINE)»(ref-167946-S16823399902004102600000) or «GENERATOR (8.1L ENGINE)»(ref-167946-S20572431032004102600000) .
10. Remove the power steering pump. Refer to «POWER STEERING PUMP REPLACEMENT (6.6 L DIESEL»(ref-188964-S41504307252005091100000) or «POWER STEERING PUMP REPLACEMENT (4.3 L)»(ref-188964-S18454437242005091100000) or «POWER STEERING PUMP REPLACEMENT (4.8L, 5.3L AND 6.0L)»(ref-188964-S01298919432005091100000) or «POWER STEERING PUMP REPLACEMENT (8.1L)»(ref-188964-S23129275222005091100000) .
11. Remove the generator bracket bolts and nut.
12. Remove the generator bracket stud.
13. Remove the generator bracket.
14. Remove the water crossover bolts.
15. Remove the water crossover.
16. Remove and discard the water crossover gaskets.
17. If replacing the water crossover remove the following: 17.1. Water outlet bolts (2) 17.2. Water outlet (1) 17.3. Thermostat (3)