Home ReviewsRefund
Home/Chevrolet/Colorado/Chevrolet Colorado I (2004-2012)/Repair manual/Cooling System (Mechanical)/Engine Cooling System
Contents Wiring diagrams Section: Cooling System (Mechanical) All sections

Engine Cooling System Chevrolet Colorado I

Cooling System (Mechanical) 11 illustrations ~6018 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Air Conditioning (A/C) Condenser to Radiator Bolt28 N.m21 lb ft
Coolant Heater50 N.m37 lb ft
Coolant Recovery Reservoir Bolt (at Wheelhouse Panel)12 N.m106 lb in
Coolant Recovery Reservoir Bolt (to Bracket)10 N.m89 lb in
Fan Blade Bolt27 N.m20 lb ft
Fan Clutch Nut56 N.m41 lb ft
Radiator Mounting Bracket Bolt28 N.m21 lb ft
Thermostat Housing Bolt10 N.m89 lb in
Water Outlet Housing Bolt10 N.m89 lb in
Water Pump Bolt10 N.m89 lb in
Water Pump Pulley Bolt25 N.m18 lb ft

Fastener Tightening Specifications

Diagnostic Starting Point - Engine Cooling

Begin the system diagnosis with the diagnostic system check. Refer to Diagnostic System Check - Vehicle . The Diagnostic System Check - Vehicle will provide the following information

  1. The identification of the control modules which command the system
  2. The ability of the control modules to communicate through the serial data circuits
  3. The identification of any stored DTCs and their status

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

Symptoms - Engine Cooling

IMPORTANTReview 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»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__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. «Engine Overheating»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system)
  2. «Loss of Coolant (2.9L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__loss-of-coolant-29l) or «Loss of Coolant (3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__loss-of-coolant-37l)
  3. «Thermostat Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system)
  4. «Coolant Heater Inoperative»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system)
  5. «Engine Fails To Reach Normal Operating Temperature»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system)
  6. «Fan Clutch Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__fan-clutch-diagnosis)

Diagnostic Aids

The engine may overheat due to an intermittent operation of the thermostat.

StepActionValuesYesNo
DEFINITION: Engine temperature lamp comes ON and stays ON, or the temperature gage shows hot, or coolant overflows from the coolant recovery reservoir onto the ground while the engine is running.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Inspect the coolant recovery reservoir for low coolant. Is there a loss of coolant?Go to Loss of Coolant (2.9L) or Loss of Coolant (3.7L)Go to Step 3
3IMPORTANT: Do not allow the engine temperature to exceed the specified value. Start the engine and allow to reach normal operating temperature.Does the engine begin to exceed the specified value?107°C (225°F)Go to Step 4Go to Diagnostic Aids
4Inspect for loose, damaged, and/or missing of the following: The A/C condenser seals The front air deflector The side seals Repair the system as necessary. Does the engine still overheat?Go to Step 5Go to Step 17
5Using the J 23688 Coolant and Battery Fluid Tester, test for insufficient coolant concentration. See Special Tools . Is the coolant protection greater than the specified value?37°C (-34°F)Go to Step 6Go to Step 7
6Correct the coolant concentration as necessary. Does the engine still overheat?Go to Step 7Go to Step 17
7Inspect for obstructed radiator air flow or bent radiator fins. Is the radiator air flow obstructed?Go to Step 8Go to Step 9
8Clean the radiator. Refer to Radiator Cleaning . Does the engine still overheat?Go to Step 9Go to Step 17
9Inspect the drive belt tensioner. Refer to Drive Belt Tensioner Diagnosis or Drive Belt Tensioner Diagnosis . Is the drive belt tensioner working properly and is the tension correct?Go to Step 11Go to Step 10
10Replace the drive belt tensioner. Refer to Drive Belt Tensioner Replacement or Drive Belt Tensioner Replacement . Does the engine still overheat?Go to Step 11Go to Step 17
11Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis . Does the thermostat operate properly?Go to Step 13Go to Step 12
12Replace the thermostat. Refer to Engine Coolant Thermostat Replacement (With 2.9L and 3.7L) . Does the engine still overheat?Go to Step 13Go to Step 17
13Inspect for an inoperative fan clutch. Refer to Fan Clutch Diagnosis . Does the engine still overheat?Go to Step 14Go to Step 17
14Inspect for blocked cooling system passages. Are the cooling system passages blocked?Go to Step 15Go to Step 16
15Replace the radiator. Refer to Radiator Replacement . Does the engine still overheat?Go to Step 16Go to Step 17
16Replace the engine water pump. Refer to Water Pump Replacement (2.9L,3.7L) . Did you complete the repair?Go to Step 17
17Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2
IMPORTANT
Do not allow the engine temperature to exceed the specified value.

Engine Overheating

Loss of Coolant (2.9L)

StepActionYesNo
DEFINITION: The cooling system is loosing coolant either internally or externally.
1Were you sent here from Symptoms or another diagnostic table?Go to Step 2Go to Symptoms - Engine Cooling
2Repair any present DTCs. Refer to Diagnostic System Check - Vehicle . Is the action complete?Go to Step 3
3Inspect the coolant level. Is the coolant at the proper level?Go to Step 6Go to Step 4
4Fill the cooling system to the proper level. Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (Vac N Fill) . Is the action complete?Go to Step 5
5If the engine is suspected to have a coolant leak into a cylinder, the coolant can hydraulically lock the engine. Does the engine crankshaft rotate?Go to Step 6Go to Step 28
6Engine overheating can cause a loss of coolant. Is the engine overheating?Go to Step 29Go to Step 7
7Extended operation with a low coolant level can cause engine internal component failure. Is the engine knocking?Go to Step 31Go to Step 8
8Idle the engine at normal operating temperature. Inspect for heavy white smoke coming out of the exhaust pipe. Is a heavy white smoke present from the exhaust pipe?Go to Step 9Go to Step 10
9Coolant in the exhaust system creates a distinctive, burning coolant odor in the exhaust. Condensation in the exhaust system can cause an odorless white smoke during engine warm up. Does the white smoke have a burning coolant type odor?Go to Step 30Go to Step 10
10With the engine idling, inspect the coolant recovery system. Does the coolant recovery system discharge coolant while the engine is idling?Go to Step 15Go to Step 11
11Visually inspect the hoses, pipes and hose clamps at the following locations: Coolant reservoir Heater core Radiator Are any of the hoses, clamps or pipes leaking?Go to Step 20Go to Step 12
12Visually inspect the following components: Block heater Coolant pressure cap Core plugs Cylinder head gaskets Engine block Intake manifold Radiator Thermostat housing Water pump Are any of the listed components leaking?Go to Step 20Go to Step 13
13Pressure test the cooling system. Refer to Cooling System Leak Testing . With the cooling system pressurized, visually inspect the components listed in steps 11 and 12. Are any leaks present?Go to Step 20Go to Step 14
14Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure?Go to Step 16Go to Step 21
15Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure?Go to Step 32Go to Step 21
16Inspect for the following conditions: A coolant smell inside of the vehicle Coolant in the HVAC module drain tube Coolant on the vehicle floor covering near the HVAC module Is coolant present?Go to Step 22Go to Step 17
17Inspect the underside of the engine oil fill cap for a gray/white milky substance. Is there a milky substance under the oil fill cap?Go to Step 18Go to Step 19
18Inspect the engine oil fluid level indicator for a gray/white milky substance. Is there a milky substance on the engine oil fluid level indicator?Go to Step 23Go to Step 19
19Inspect the automatic transmission oil fluid level indicator, if equipped, for a gray/white milky substance. Is there a milky substance on the automatic transmission fluid level indicator?Go to Step 25Go to Step 33
20Repair or replace the leaking component. Refer to the appropriate repair. Is the repair complete?Go to Step 33
21Replace the coolant pressure cap. Is the repair complete?Go to Step 33
22Replace the heater core. Refer to Heater Core Replacement . Is the repair complete?Go to Step 33
23Remove the engine oil cooler lines from the radiator. Pressure test the cooling system. Refer to Cooling System Leak Testing . Inspect the engine oil cooler for coolant. Is coolant present?Go to Step 24Go to Step 27
24Replace the radiator. Refer to Radiator Replacement . Service the engine oil and filter. Refer to Engine Oil and Oil Filter Replacement . Is the repair complete?Go to Step 33
25Remove the transmission oil cooler lines from the radiator. Pressure test the cooling system. Refer to Cooling System Leak Testing . Inspect the transmission oil cooler for coolant. Is coolant present?Go to Step 26Go to Step 27
26Replace the radiator. Refer to Radiator Replacement . Service the automatic transmission. Refer to Engine Coolant/Water in Transmission . Is the repair complete?Go to Step 33
27Install the cooler lines to the radiator. Is the action complete?Go to Step 33
28Repair the engine no crank condition. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate . Is the repair complete?Go to Step 33
29Repair the engine overheating condition. Refer to Engine Overheating . Is the repair complete?Go to Step 33
30Repair the engine internal coolant leak. Refer to Coolant in Combustion Chamber or Coolant in Engine Oil . Is the repair complete?Go to Step 33
31Repair the engine knock. Is the repair complete?Go to Step 33
32Repair the combustion pressure in the cooling system problem. Refer to Cylinder Leakage Test . Is the repair complete?Go to Step 33
33Operate the system in order to verify the repair. Did you find and correct the condition?System OKGo to Step 2

Loss of Coolant (2.9L)

Loss of Coolant (3.7L)

StepActionYesNo
DEFINITION: The cooling system is losing coolant either internally or externally.
1Were you sent here from Symptoms or another diagnostic table?Go to Step 2Go to Symptoms - Engine Cooling
2Repair any present DTCs. Refer to Diagnostic System Check - Vehicle . Is the action complete?Go to Step 3
3Inspect the coolant level. Is the coolant at the proper level?Go to Step 6Go to Step 4
4Fill the cooling system to the proper level. Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (Vac N Fill) . Is the action complete?Go to Step 5
5If the engine is suspected to have a coolant leak into a cylinder, the coolant can hydraulically lock the engine. Does the engine crankshaft rotate?Go to Step 6Go to Step 30
6Engine overheating can cause a loss of coolant. Is the engine overheating?Go to Step 31Go to Step 7
7Extended operation with a low coolant level can cause engine internal component failure. Is the engine knocking?Go to Step 33Go to Step 8
8Idle the engine at normal operating temperature. Inspect for heavy white smoke coming out of the exhaust pipe. Is a heavy white smoke present from the exhaust pipe?Go to Step 9Go to Step 10
9Coolant in the exhaust system creates a distinctive, burning coolant odor in the exhaust. Condensation in the exhaust system can cause an odorless white smoke during engine warm up. Does the white smoke have a burning coolant type odor?Go to Step 32Go to Step 10
10With the engine idling, inspect the coolant recovery system. Does the coolant recovery system discharge coolant while the engine is idling?Go to Step 15Go to Step 11
11Visually inspect the hoses, pipes and hose clamps at the following locations: Coolant reservoir Heater core Radiator Are any of the hoses, clamps or pipes leaking?Go to Step 22Go to Step 12
12Visually inspect the following components: Block heater Coolant pressure cap Core plugs Cylinder head gaskets Engine block Intake manifold Radiator Thermostat housing Water pump Are any of the listed components leaking?Go to Step 22Go to Step 13
13Pressure test the cooling system. Refer to Cooling System Leak Testing . With the cooling system pressurized, visually inspect the components listed in steps 11 and 12. Are any leaks present?Go to Step 22Go to Step 14
14Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure?Go to Step 16Go to Step 23
15Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure?Go to Step 34Go to Step 23
16Inspect for the following conditions: A coolant smell inside of the vehicle Coolant in the HVAC module drain tube Coolant on the vehicle floor covering near the HVAC module Is coolant present?Go to Step 24Go to Step 17
17Add 30 ml (1 oz) of coolant leak detection dye GM P/N 89022219 (Canadian P/N 89022220) to the cooling system for each 15 L (4 gal) of coolant. Refer to Approximate Fluid Capacities . Start the vehicle and allow the engine to reach normal operating temperature. Shut the engine off. Use J 42220 Universal 12V Leak Detection Lamp to visually inspect the components listed in steps 11 and 12. See Special Tools . Are any leaks present?Go to Step 22Go to Step 18
18Use J 42220 to inspect for the following conditions:. See Special Tools . Coolant dye in the HVAC module drain tube Coolant dye on the vehicle floor covering near the HVAC module Is coolant dye present?Go to Step 24Go to Step 19
19Inspect the underside of the engine oil fill cap for a gray/white milky substance. Is there a milky substance under the oil fill cap?Go to Step 20Go to Step 21
20Inspect the engine oil fluid level indicator for a gray/white milky substance. Is there a milky substance on the engine oil fluid level indicator?Go to Step 25Go to Step 21
21Inspect the automatic transmission oil fluid level indicator, if equipped, for a gray/white milky substance. Is there a milky substance on the automatic transmission fluid level indicator?Go to Step 27Go to Step 35
22Repair or replace the leaking component. Refer to the appropriate repair. Is the repair complete?Go to Step 35
23Replace the coolant pressure cap. Is the repair complete?Go to Step 35
24Replace the heater core. Refer to Heater Core Replacement . Is the repair complete?Go to Step 35
25Remove the engine oil cooler lines from the radiator. Pressure test the cooling system. Refer to Cooling System Leak Testing . Inspect the engine oil cooler for coolant. Is coolant present?Go to Step 26Go to Step 29
26Replace the radiator. Refer to Radiator Replacement . Service the engine oil and filter. Refer to Engine Oil and Oil Filter Replacement . Is the repair complete?Go to Step 35
27Remove the transmission oil cooler lines from the radiator. Pressure test the cooling system. Refer to Cooling System Leak Testing . Inspect the transmission oil cooler for coolant. Is coolant present?Go to Step 28Go to Step 29
28Replace the radiator. Refer to Radiator Replacement . Service the automatic transmission. Refer to Engine Coolant/Water in Transmission . Is the repair complete?Go to Step 35
29Install the cooler lines to the radiator. Is the action complete?Go to Step 35
30Repair the engine no crank condition. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate . Is the repair complete?Go to Step 35
31Repair the engine overheating condition. Refer to Engine Overheating . Is the repair complete?Go to Step 35
32Repair the engine internal coolant leak. Refer to Coolant in Engine Oil . Is the repair complete?Go to Step 35
33Repair the engine knock. Refer to Lower Engine Noise, Regardless of Engine Speed . Is the repair complete?Go to Step 35
34Repair the combustion pressure in the cooling system problem. Refer to Cylinder Leakage Test . Is the repair complete?Go to Step 35
35Operate the system in order to verify the repair. Did you find and correct the condition?System OKGo to Step 2

Loss of Coolant (3.7L)

Scheme 1

Scheme 1: Thermostat Test Procedure Using Tempilsticks
Scheme 1: Thermostat Test Procedure Using Tempilsticks

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 (4).

Tools Required

J 24731 Tempilstick. See Special Tools .

  1. Use a tempilstick in order to find the opening and the closing temperatures of the coolant thermostat. J 24731-188 tempilstick melts at 87°C (188°F). The thermostat should begin to open at 90°C (194°F). J 24731-206 tempilstick melts at 97°C (206°F). The thermostat should be fully open at 107°C (225°F).
  2. Replace the coolant thermostat if it does not operate properly between this temperature range. Refer to «Engine Coolant Thermostat Replacement (With 2.9L and 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Circuit/System Description

The optional coolant heater operates using 110 volt AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather. There is an internal thermal switch in the power cord that prevents operation above -18°C (0°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. 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.

Reference Information

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
  2. «Connector Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
  3. «Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Circuit/System Testing

IMPORTANTThe power supply cord will read open due to an internal thermal switch if the ambient temperature is above -18°C (0°F).
  1. Test the engine coolant heater for an open or short to ground. If open or shorted, replace the heater.
  2. If the heater tests normal, replace the coolant heater power cord.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Coolant Heater Replacement (2.9L,3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system)
  2. «Coolant Heater Cord Replacement (2.9L,3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system)

The engine may fail to reach normal operating temperature due to an intermittent operation of the thermostat.

StepActionYesNo
DEFINITION: Normal coolant temperature readings will be expected to vary from 92-107°C (198-225°F).
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Verify that the engine fails to reach normal operating temperature. Is the engine failing to reach normal operating temperature?Go to Step 3Go to Diagnostic Aids
3Inspect the coolant recovery reservoir for low coolant. Is there a loss of coolant?Go to Loss of Coolant (2.9L) or Loss of Coolant (3.7L)Go to Step 4
4Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis . Does the thermostat operate properly?Go to Step 6Go to Step 5
5Replace the thermostat. Refer to Engine Coolant Thermostat Replacement (With 2.9L and 3.7L) . Did you complete the repair?Go to Step 6
6Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2

Engine Fails To Reach Normal Operating Temperature

J 24460-01 Cooling System Pressure Tester. See Special Tools .

  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. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  4. Test the pressure cap for the following conditions: Pressure release when the J 24460-01 exceeds the pressure rating of the pressure cap. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) . 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.

J 24460-01 Cooling System Pressure Tester. See Special Tools .

  1. Remove the pressure cap.
  2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. Use the J 24460-01 in order to apply pressure to the cooling system. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) . Do not exceed the pressure cap rating.
  4. The cooling system should hold the rated pressure for at least 2 minutes. Observe the gage for any pressure loss.
  5. Repair any leaks as required.

Fan Clutch Diagnosis

StepActionYesNo
DEFINITION: Testing the engagement and disengagement of the fan clutch.
1Were you sent here from Symptoms or another diagnostic table?Go to Step 2Go to Symptoms - Engine Cooling
2Is there excessive fan air noise?Go to Step 3Go to Step 4
3Fan air noise is normal during cold engine start up. Does the fan noise go away at normal engine operating temperature?Go to Step 13Go to Step 4
4IMPORTANT: The engine must be turned off and the engine temperature should be cold. Rotate the fan clutch.Does the fan clutch rotate?Go to Step 5Go to Step 14
5Visually inspect the fan blades for cracks, looseness or damage. Are the fan blades in good condition?Go to Step 6Go to Step 15
6Visually inspect the fan clutch for signs of silicone leakage. Slight silicone leakage may not effect the fan clutch engagement. Excessive leakage will prevent the fan clutch from engaging. Is the silicone fluid leakage excessive?Go to Step 14Go to Step 7
7Inspect the fan clutch for proper installation. Move the fan blade back and forth in a lateral motion. Inspect for fan blade to fan clutch movement. Is the fan blade loose at the fan clutch?Go to Step 10Go to Step 8
8Inspect the fan clutch for wear. Move the fan blade back and forth in a lateral motion. IMPORTANT: Approximately 6.5 mm (1/4 in) movement at the tip of the fan blade is normal. Inspect for fan clutch lateral movement. Is the fan clutch lateral movement excessive?Go to Step 14Go to Step 9
9The fan clutch should have more turning resistance when the engine is at or above normal operating temperature. Does the fan clutch have more resistance when the engine temperature is raised?Go to Step 11Go to Step 14
10Tighten the fan. Refer to Fastener Tightening Specifications . Is the repair complete?Go to Step 16
11Perform a fan clutch engagement test. Ensure the engine coolant level is full. Ensure the cooling fan drive belt tension is correct and not slipping. Position and secure a thermometer between the fan clutch and the radiator. Ensure the cooling fan is disengaged before starting this test. Sufficiently cover the radiator grille to restrict the air flow. IMPORTANT: Do not allow engine temperature to exceed 121°C (250°F). Start the engine. Turn the A/C ON, if equipped. Operate the engine at approximately 2,000 RPM. Note the thermometer reading when the fan clutch engages. Do not continue this test if the fan clutch does not engage between 85-96°C (185-205°F). Fan clutch engagement will be indicated by an increase in fan air noise, fan speed, and a temperature drop of about 3-10°C (5-15°F) on the thermometer. Did the fan clutch engage between 85-96°C (185-205°F)?Go to Step 12Go to Step 14
12Once the fan clutch engages, perform the following steps: Uncover the radiator grille. Turn the A/C OFF, if equipped. Operate the engine at approximately 2,500 RPM to reduce the engine operating temperature. Remove the thermometer. Did the engine return to normal operating temperature?Go to Step 13
13As the engine temperature returns to normal, the fan clutch will disengage, indicated by a reduction in fan air noise and fan speed. Did the fan clutch disengage?Go to Step 16Go to Step 14
14Replace the fan clutch. Refer to Fan Clutch Replacement . Is the repair complete?Go to Step 16
15Replace the fan blades. Refer to Fan Clutch Replacement . Is the repair complete?Go to Step 16
16Operate the fan clutch to verify proper operation. Did you find and correct the condition?System OKGo to Step 2
IMPORTANT
The engine must be turned off and the engine temperature should be cold.
IMPORTANT
Approximately 6.5 mm (1/4 in) movement at the tip of the fan blade is normal.
IMPORTANT
Do not allow engine temperature to exceed 121°C (250°F).

Fan Clutch Diagnosis

Cooling System Draining and Filling (Static Fill)

Special Tools

  1. J 26568 Coolant and Battery Tester. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. J 38185 Hose Clamp Pliers. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .

Draining Procedure

  1. Park the vehicle on a level surface.
  2. Allow the engine to cool.
  3. Remove the radiator cap.
  4. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/colorado/i-2004-2012/remont/hoistjack/#general-information) .
  5. Place a drain pan under the lower radiator hose connection at the bottom of the radiator.
  6. Using J 38185 lock open the hose clamp back on the lower radiator hose. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  7. Slowly remove the lower radiator hose and drain the coolant into the drain pan.
  8. Inspect the engine coolant for the following: Discolored appearance-Follow the flush procedure. Refer to «Flushing»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__flushing) . Normal in appearance-Follow the filling procedure. If a complete block drain is required, remove the coolant heater located on the LH side of the block. Refer to «Coolant Heater Replacement (2.9L,3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .

Filling Procedure

Note. The procedure below must be followed. Improper coolant level could result in a low or high coolant level condition, causing engine damage.

  1. If a complete block drain was required, install the coolant heater. Refer to «Coolant Heater Replacement (2.9L,3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. Install the lower radiator hose.
  3. Using the J 38185 slide the lower radiator hose clamp into the original position. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  4. Lower the vehicle.
  5. Install the radiator cap.
  6. Remove coolant recovery reservoir cap.
  7. Fill the coolant recovery reservoir with the remaining coolant.
  8. Install coolant recovery reservoir cap.
  9. Start the engine.
  10. Run the engine at 2,000-2,500 RPM until the engine reaches normal operating temperature.
  11. Allow the engine to idle for 3 minutes.
  12. Shut the engine off.
  13. Allow the engine to cool.
  14. Top off the coolant recovery reservoir as necessary.
  15. Inspect the cooling system for leaks.
  16. Rinse away any excess coolant from the engine and the engine compartment.
  17. Inspect the concentration of the engine coolant using J 26568 . See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .

Cooling System Draining and Filling (Vac N Fill)

Special Tools

  1. GE-47716 Vac N Fill Coolant Refill Tool. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. J 26568 Coolant and Battery Tester. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. J 38185 Hose Clamp Pliers. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  4. J 42401 Radiator Cap and Surge Tank Test Adapter. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  1. Park the vehicle on a level surface.
  2. Allow the engine to cool.
  3. Remove the radiator cap.
  4. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/colorado/i-2004-2012/remont/hoistjack/#general-information) .
  5. Place a drain pan under the lower radiator hose connection at the bottom of the radiator.
  6. Using J 38185 lock open the hose clamp back on the lower radiator hose. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  7. Slowly remove the lower radiator hose and drain the coolant into the drain pan.
  8. Inspect the engine coolant for the following: Discolored appearance-Follow the flush procedure. Refer to «Flushing»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__flushing) . Normal in appearance-Follow the filling procedure. If a complete block drain is required, remove the coolant heater located on the LH side of the block. Refer to «Coolant Heater Replacement (2.9L,3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  1. Install the J 42401 . See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. Attach the Vac N Fill cap to the vehicle's coolant fill port.
  3. Attach the vacuum gage assembly to the Vac N Fill cap.
  4. Attach the fill hose to the barb fitting on the vacuum gage assembly. Ensure that the valve is closed.
  5. Pour the coolant mixture into the graduated reservoir.
  6. Place the fill hose in the graduated reservoir.
  7. Install the vacuum tank on the graduated reservoir with the fill hose routed through the cut-out area in the vacuum tank.
  8. Attach the venturi assembly to the vacuum tank.
  9. Attach a shop air hose to the venturi assembly. Ensure the valve on the venturi assembly is closed.
  10. Attach the vacuum hose to the vacuum gage assembly and the vacuum tank.
  11. Clamp off the overflow hose.
  12. Open the valve on the venturi assembly. The vacuum gage will begin to rise and a hissing noise will be present.
  13. Continue to draw vacuum until the needle stops rising. This should be 610-660 mm Hg (24-26 in Hg).
  14. To aid in the fill process, position the graduated reservoir above the coolant fill port.
  15. Slowly open the valve on the vacuum gage assembly. When the coolant reaches the top of the fill hose, close the valve. This will eliminate air from the fill hose.
  16. Close the valve on the venturi assembly.
  17. If there is a suspected leak in the cooling system, allow the system to stabilize under vacuum and monitor for vacuum loss. If vacuum loss is observed, refer to «Loss of Coolant (2.9L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__loss-of-coolant-29l) or «Loss of Coolant (3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__loss-of-coolant-37l) .
  18. Open the valve on the vacuum gage assembly. The vacuum gage will drop as coolant is drawn into the system.
  19. Once the vacuum gage reaches zero, close the valve on the vacuum gage assembly and repeat steps 11-17.
  20. Remove the J 42401 . See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  21. Detach the Vac N Fill cap from the vehicle's coolant fill port.
  22. Add coolant to the system as necessary.
  23. Inspect the concentration of the coolant mixture using J 26568 . See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  24. Detach the vacuum hose from the vacuum gage assembly.
  25. Attach the extraction hose to the vacuum hose.
  26. Open the valve on the venturi assembly to start a vacuum draw.
  27. Use the extraction hose to draw out coolant to the proper level.
  28. The vacuum tank has a drain valve on the bottom of the tank. Open the valve to drain coolant from the vacuum tank into a suitable container for disposal.

Flushing

IMPORTANTDo not use a chemical flush.

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.

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 instruction. Always remove the thermostat before flushing the cooling system.

When the cooling system becomes contaminated, the cooling system should be flushed thoroughly to remove the contaminants before the engine is seriously damaged.

  1. Drain the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  2. Remove the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. Clean and flush the coolant recovery reservoir with clean, drinkable water.
  4. Install the coolant recovery reservoir. Refer to «Coolant Recovery Reservoir Replacement»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  5. Follow the drain and fill procedure using only clean, drinkable water. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  6. Run the engine for 20 minutes.
  7. Stop the engine.
  8. Drain the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  9. Repeat the procedure if necessary, until the fluid is nearly colorless.
  10. Fill the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .

Radiator Cleaning

CAUTIONNEVER spray water on a hot heat exchanger. The resulting steam could cause personal injury.

Note. The heat exchanger fins are necessary for good heat transfer. Do not brush the fins. This may cause damage to the fins, reducing heat transfer.

  1. Some conditions may require the use of warm water and a mild detergent.
  2. Clean the A/C condenser fins.
  3. Clean between the A/C condenser and radiator.
  4. Clean the radiator cooling fins.
  5. Straighten any damaged cooling fins.

Removal Procedure

  1. Partially drain the coolant. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  2. Remove the air cleaner assembly. Refer to «Air Cleaner Assembly Replacement»(/chevrolet/colorado/i-2004-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-29l-introduction-2-of-2) or «Air Cleaner Assembly Replacement»(/chevrolet/colorado/i-2004-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-37l-introduction-2-of-2) .
  3. Remove the coolant overflow hose (6) from the coolant recovery reservoir (5).
  4. Remove the bolt (4) securing the coolant recovery reservoir (5) to the coolant recovery reservoir bracket.
  5. Remove the radiator vent hose from the coolant recovery reservoir.
  6. Remove the bolt securing the coolant recovery reservoir (5) to the front wheel house panel.
  7. Remove the coolant recovery reservoir.

Installation Procedure

  1. Install the coolant recovery reservoir.
  2. Install the retaining bolt to the front wheelhouse panel. Tighten: Tighten the bolt to 12 N.m (106 lb in).
  3. Install the radiator vent hose to the coolant recovery reservoir.
  4. Install the bolt (4) securing the coolant recovery reservoir (5) to the coolant recovery reservoir bracket. Tighten: Tighten the nut to 10 N.m (88 lb in).
  5. Install the overflow hose (6) to the coolant recovery reservoir (5).
  6. Install the air cleaner assembly. Refer to «Air Cleaner Assembly Replacement»(/chevrolet/colorado/i-2004-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-29l-introduction-2-of-2) or «Air Cleaner Assembly Replacement»(/chevrolet/colorado/i-2004-2012/remont/testing-diagnostics/#engine-control-system-fuel-system-37l-introduction-2-of-2) .
  7. Fill the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .

J 38185 Hose Clamp Pliers. See Special Tools .

  1. Drain the engine coolant. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  2. Using J 38185 reposition the inlet radiator hose clamp (2) away from the radiator. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. Remove the inlet radiator hose from the radiator.
  4. Using J 38185 reposition the inlet radiator hose clamp (1) away from the engine. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  5. Remove the inlet radiator hose from the engine.
  1. Install the inlet radiator hose to the engine.
  2. Using J 38185 reposition the inlet radiator hose clamp (1) to the engine. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. Install the inlet radiator hose to the radiator.
  4. Using J 38185 reposition the inlet radiator hose clamp (2) to the radiator. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  5. Fill the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .

J 38185 Hose Clamp Pliers. See Special Tools .

  1. Drain the coolant. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  2. Using J 38185 reposition the outlet radiator hose clamp away from the thermostat housing (1). See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. Remove the outlet radiator hose from the thermostat.
  4. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/colorado/i-2004-2012/remont/hoistjack/#general-information) .
  5. Using J 38185 reposition the outlet radiator hose clamp away from the radiator. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  6. Remove the outlet radiator hose (1) from the radiator.
  1. Install the outlet radiator hose (1) to the radiator.
  2. Using J 38185 reposition the outlet radiator hose clamp to the radiator. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. Lower the vehicle.
  4. Install the outlet radiator hose to the thermostat (1).
  5. Using J 38185 reposition the outlet radiator hose clamp to the thermostat housing. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  6. Fill the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  1. Partially drain the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  2. Remove the vent inlet hose from the radiator.
  3. Remove the retaining clips from the radiator vent inlet hose.
  4. Remove the radiator vent inlet hose (3) from the coolant recovery reservoir (2).
  1. Install the radiator vent inlet hose (3) to the coolant recovery reservoir (2).
  2. Install the retaining clips to the radiator vent inlet hose.
  3. Install the radiator vent inlet hose to the radiator.
  4. Fill the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .

Fan Replacement (2.9L, 3.7L)

Tools Required

  1. J 41240-5A Fan Clutch Wrench. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. J 46406 Fan Clutch Remover and Installer
  1. Remove the fan shroud. Refer to «Fan Shroud Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. Install the J 46406 and the J 41240-5A to the fan clutch. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. Remove the fan hub nut in a counterclockwise rotation.
  1. Install the J 46406 and the J 41240-5A to the fan clutch. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. Install the fan hub nut to the pulley and hand tighten in a clockwise rotation. Tighten: Tighten the fan clutch nut clockwise to 56 N.m (41 lb ft).
  3. Install the fan shroud. Refer to «Fan Shroud Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  1. Remove the cooling fan. Refer to «Fan Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__fan-replacement-29l-37l) .
  2. Remove the bolts retaining the fan blade to the fan clutch.
  3. Separate the fan blade from the fan clutch.
  1. Assemble the fan to the fan clutch.
  2. Install the 4 bolts to the fan blade and tighten. Tighten: Tighten the bolts to 27 N.m (20 lb ft).
  3. Install the cooling fan. Refer to «Fan Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__fan-replacement-29l-37l) .

J 38185 Hose Clamp Pliers. See Special Tools .

  1. Drain the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  2. Raise and support the vehicle only high enough to access the thermostat housing (4) through the wheelhouse. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/colorado/i-2004-2012/remont/hoistjack/#general-information) .
  3. Remove the left wheelhouse liner. Refer to «Front Wheelhouse Liner Replacement»(/chevrolet/colorado/i-2004-2012/remont/frames-subframes-crossmembers/#frame-and-underbody) .
  4. Position the J 38185 to the clamp (3) in order to remove the radiator inlet hose (2) from the thermostat housing (4). See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  5. Remove the thermostat housing bolts.
  6. Remove the thermostat housing from the engine block.
  7. Clean and inspect the thermostat housing.
  8. Clean and inspect the sealing surface of the engine block.
  1. Position the thermostat housing to the engine block.
  2. Install the thermostat housing bolts. Tighten: Tighten the thermostat housing bolts to 10 N.m (89 lb in).
  3. Position the J 38185 to the clamp (3) in order to connect the radiator inlet hose (2) to the thermostat housing (4). See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  4. Install the left wheelhouse liner. Refer to «Front Wheelhouse Liner Replacement»(/chevrolet/colorado/i-2004-2012/remont/frames-subframes-crossmembers/#frame-and-underbody) .
  5. Lower the vehicle.
  6. Fill the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  7. Inspect all sealing surfaces for leaks after starting the engine.

J 38185 Hose Clamp Pliers. See Special Tools .

  1. Drain the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  2. Position the J 38185 to the clamp (8) in order to remove the radiator outlet hose (7) from the water outlet housing. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  3. Remove the power steering pump bracket. Refer to «Power Steering Pump Bracket Replacement»(/chevrolet/colorado/i-2004-2012/remont/manual-power-steering/#power-steering-system) .
  4. Remove the water outlet housing bolts.
  5. Remove the water outlet housing from the cylinder head.
  6. Clean and inspect the water outlet housing.
  7. Clean and inspect the sealing surface of the cylinder head.
  1. Position the water outlet housing to the cylinder head.
  2. Install the water outlet housing bolts. Tighten: Tighten the bolts to 10 N.m (89 lb in).
  3. Install the power steering pump bracket. Refer to «Power Steering Pump Bracket Replacement»(/chevrolet/colorado/i-2004-2012/remont/manual-power-steering/#power-steering-system) .
  4. Position the J 38185 to the clamp (8) in order to connect the radiator outlet hose (7) to the water outlet housing. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  5. Fill the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  6. Inspect all sealing surfaces for leaks after starting the engine.

Tool Required

J 46406 Fan Clutch Remover and Installer

  1. Drain the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  2. Remove the fan. Refer to «Fan Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__fan-replacement-29l-37l) .
  3. Remove the drive belt. Refer to «Drive Belt Replacement»(/chevrolet/colorado/i-2004-2012/remont/mechanical/#engine-mechanical-29l) or «Drive Belt Replacement»(/chevrolet/colorado/i-2004-2012/remont/mechanical/#engine-mechanical-37l) .
  4. Using the J 46406 , secure the water pump pulley and remove the water pump pulley bolts.
  5. Remove the J 46406 .
  6. Remove the water pump pulley.
  7. Remove the water pump bolts.
  8. Remove the water pump.
  9. Discard the gasket.
  1. Install a new water pump gasket.
  2. Position the water pump to the engine.
  3. Install the water pump bolts. Tighten: Tighten the bolts to 10 N.m (89 lb in).
  4. Install the water pump pulley.
  5. Install the water pump pulley bolts.
  6. Using the J 46406 , secure the water pump pulley while tightening the water pump pulley bolts. Tighten: Tighten the bolts to 25 N.m (18 lb ft).
  7. Remove the J 41240 . See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  8. Install the drive belt. Refer to «Drive Belt Replacement»(/chevrolet/colorado/i-2004-2012/remont/mechanical/#engine-mechanical-29l) or «Drive Belt Replacement»(/chevrolet/colorado/i-2004-2012/remont/mechanical/#engine-mechanical-37l) .
  9. Install the fan. Refer to «Fan Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__fan-replacement-29l-37l) .
  10. Fill the cooling system with the specified coolant and concentration. Refer to «Cooling System Draining and Filling (Static Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-static) or «Cooling System Draining and Filling (Vac N Fill)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system__cooling-system-draining-and-filling-vac) .
  11. Inspect for leaks.
  1. Remove the radiator hose-outlet. Refer to «Radiator Outlet Hose Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. Release the differential vent hose retainer.
  3. Release the A/C suction hose retainer.
  4. Release the A/C discharge hose retainer.
  5. Rotate the slip ring counterclockwise from under the fan shroud.
  6. Remove the fan shroud (3).
  1. Install the fan shroud (3) to the vehicle.
  2. Rotate the slip ring to the original position.
  3. Install the differential vent hose retainer.
  4. Install the A/C suction hose retainer.
  5. Install the A/C discharge hose retainer.
  6. Install the radiator hose-outlet. Refer to «Radiator Outlet Hose Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .

Special Tools

J 38185 Hose Clamp Pliers. See Special Tools .

  1. Remove the fan shroud. Refer to «Fan Shroud Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  2. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/colorado/i-2004-2012/remont/hoistjack/#general-information) .
  3. Using J 38185 reposition the radiator outlet hose clamp (2) from the radiator. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  4. Remove the outlet radiator hose (1) from the radiator.
  5. Remove the transmission cooler lines from the radiator. Refer to «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Disconnection and Connection»(/chevrolet/colorado/i-2004-2012/remont/automatic-trans/#how-to-overhaul-the-automatic-transmission-4l60-e4l65-e4l70-e-removal-installation-service-troubleshooting-diagnosis) .
  6. Lower the vehicle.
  7. Remove the radiator vent inlet hose from the radiator.
  8. Remove the radiator mounting bracket bolt.
  9. Remove the radiator mount.
  10. Remove the grill.
  11. Remove the condenser mounting bolts.
  12. Separate the condenser from the radiator.
  13. Remove the radiator.
  1. Install the radiator.
  2. Install the condenser to the radiator.
  3. Install the bolts retaining the condenser to the radiator. Tighten: Tighten the bolts to 28 N.m (21 lb ft).
  4. Install the grille.
  5. Install the radiator mount bracket.
  6. Install the radiator mounting bracket bolt. Tighten: Tighten the bolts to 28 N.m (21 lb ft).
  7. Raise the vehicle.
  8. Install the radiator outlet hose (1) to the radiator.
  9. Using J 38185 reposition the radiator outlet hose clamp (2) to the radiator. See «Special Tools»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  10. Connect the transmission cooler lines to the radiator. Refer to «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Disconnection and Connection»(/chevrolet/colorado/i-2004-2012/remont/automatic-trans/#how-to-overhaul-the-automatic-transmission-4l60-e4l65-e4l70-e-removal-installation-service-troubleshooting-diagnosis) .
  11. Lower the vehicle.
  12. Install the radiator vent inlet hose to the radiator.
  13. Install the fan shroud. Refer to «Fan Shroud Replacement (2.9L, 3.7L)»(/chevrolet/colorado/i-2004-2012/remont/cooling-system-mechanical/#engine-cooling-system) .
  1. Raise and support the vehicle only high enough to access the coolant heater (6) through the wheelhouse. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/colorado/i-2004-2012/remont/hoistjack/#general-information) .
  2. Remove the left wheelhouse liner. Refer to «Front Wheelhouse Liner Replacement»(/chevrolet/colorado/i-2004-2012/remont/frames-subframes-crossmembers/#frame-and-underbody) .
  3. Disconnect the coolant heater cord (4) from the coolant heater (6).
  4. Remove the coolant heater from the engine block.
  1. Locate the block heater hole on side of block.
  2. While lining up the retaining clip on the block heater to notch on block, insert the block heater and snap into place.
  3. Connect the coolant heater cord (4) to the coolant heater (6).
  4. Install the left wheelhouse liner. Refer to «Front Wheelhouse Liner Replacement»(/chevrolet/colorado/i-2004-2012/remont/frames-subframes-crossmembers/#frame-and-underbody) .
  5. Lower the vehicle.
  1. Remove the battery box. Refer to «Battery Box Replacement»(/chevrolet/colorado/i-2004-2012/remont/charging-system/#battery-charging-system-and-starting-system) .
  2. Disconnect the coolant heater cord (4) from the coolant heater (6).
  3. Cut the coolant heater cord ties (2, 5) from the following: The battery cables conduit (3) The engine wiring harness conduit (1)
  4. Remove the coolant heater cord (4) from the vehicle.
  1. Position the coolant heater cord (4) to the engine.
  2. Route the coolant heater cord (4) along the engine wiring harness conduit (1) and battery cables conduit (3).
  3. Connect the coolant heater cord (4) to the coolant heater (6).
  4. Secure the coolant heater cord ties (2, 5) to the following: The battery cables conduit (3) The engine wiring harness conduit (1)
  5. Install the battery box. Refer to «Battery Box Replacement»(/chevrolet/colorado/i-2004-2012/remont/charging-system/#battery-charging-system-and-starting-system) .
  6. Place the remaining coolant heater cord (4) between the following: The battery box The underhood fuse block

Coolant Heater

The optional engine coolant heater (RPO K05) operates using 110-volt AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather -29°C (-20°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. 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 systems 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.

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 normal 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 2 tanks. The aluminum core is a tube and fin crossflow 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.

Pressure Cap

The pressure cap seals the cooling system. It contains a blow off or pressure 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.

Coolant Recovery System

The coolant recovery system consists of a plastic coolant recovery reservoir and overflow tube. 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 bubbles absorbs heat much better than coolant with bubbles.

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 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. Its 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 the 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 the rated thermostat opening temperature, the thermostat valve remains closed. This prevents circulation of the coolant to the radiator and allows the engine to warm up. After the coolant temperature reaches the rated thermostat opening temperature, the thermostat valve will open. The coolant is then allowed to circulate through the thermostat 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.

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.

Special Tools Illustration Tool Number/ Description GE 47716 Vac N Fill Coolant Refill Tool EN 48543 Fan Clutch Holding Tool J 23688 Coolant and Battery Fluid Tester J 24460-01 Cooling System Pressure Tester J 24731 Tempil Stick J 26568 Coolant and Battery Fluid Tester J 38185 Hose Clamp Pliers J 41240 Fan Clutch Remover and Installer J 41240-5A Fan Clutch Wrench J 42220 Universal 12V Leak Detection Lamp J 42401 Radiator Cap and Surge Tank Test Adapters J 43244 Relay Puller Pliers

Scheme 2

Scheme 2: Special Tools
Scheme 2: Special Tools

Scheme 3

Scheme 3
Scheme 3

Scheme 4

Scheme 4
Scheme 4

Scheme 5

Scheme 5
Scheme 5

Scheme 6

Scheme 6
Scheme 6

Scheme 7

Scheme 7
Scheme 7

Scheme 8

Scheme 8
Scheme 8

Scheme 9

Scheme 9
Scheme 9

Scheme 10

Scheme 10
Scheme 10

Scheme 11

Scheme 11
Scheme 11

See also:
• Diagnostic System Check - Vehicle
• Checking Aftermarket Accessories
• Testing for Intermittent Conditions and Poor Connections
• Drive Belt Tensioner Diagnosis
• Drive Belt Tensioner Diagnosis
• Heater Core Replacement
• Engine Coolant/Water in Transmission
• Engine Will Not Crank - Crankshaft Will Not Rotate
• Coolant in Combustion Chamber
• Coolant in Engine Oil
• Approximate Fluid Capacities
• Engine Will Not Crank - Crankshaft Will Not Rotate
• Coolant in Engine Oil
• Lower Engine Noise, Regardless of Engine Speed
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Circuit Testing
• Connector Repairs
• Wiring Repairs
• Diagnostic Repair Verification
• Lifting and Jacking the Vehicle
• Air Cleaner Assembly Replacement
• Air Cleaner Assembly Replacement
• Fastener Notice
• Front Wheelhouse Liner Replacement
• Power Steering Pump Bracket Replacement
• Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Disconnection and Connection
• Battery Box Replacement
• Cooling System Description and Operation
• Loss of Coolant (2.9L)
• Loss of Coolant (3.7L)
• Fan Clutch Diagnosis
• Radiator Cleaning
• Symptoms - Engine Cooling
• Cooling System Draining and Filling (Static Fill)
• Cooling System Draining and Filling (Vac N Fill)
• Fastener Tightening Specifications
• Flushing
• Fan Replacement (2.9L, 3.7L)