Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 226 (ENGINE COOLING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESENGINE OVERHEATINGDIAGNOSTIC AIDS
2008 Chevrolet Chevy Express G3500, Van Passenger Extended
Diagnostic Aids
2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Diagnostic Aids
WARNING: This page is about a different car, the 2008 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
The engine may overheat due to an intermittent operation of one of the following components:
- The after boil heater pump
- The coolant bypass solenoid
- The coolant bypass valve
- The mechanical cooling fan
- The electric cooling fans
- The thermostat
For electrical inspection of the cooling fans and the after boil heater pump, refer to Testing for Intermittent Conditions and Poor Connections .
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| DEFINITION: Engine temperature lamp comes ON and stays ON, or the temperature gage shows hot, or coolant overflows from the surge tank onto the ground while the engine is running. | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | - | Go to Step 2 | Go to Diagnostic System Check - Vehicle |
| 2 | Inspect the surge tank for low coolant. Is there a loss of coolant? |
- | Go to Loss of Coolant (LC3) or Loss of Coolant (LH2, LY7, LLT) | Go to Step 3 |
| 3 |
IMPORTANT:
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 4 | Go to Diagnostic Aids |
| 4 |
|
- | Go to Step 5 | Go to Step 18 |
| 5 | Using 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 6 | Go to Step 7 |
| 6 | Correct the coolant concentration as necessary. Does the engine still overheat? |
- | Go to Step 7 | Go to Step 18 |
| 7 | Inspect for obstructed radiator air flow or bent radiator fins. Is the radiator air flow obstructed? |
- | Go to Step 8 | Go to Step 9 |
| 8 | Clean the radiator. Refer to Radiator Cleaning (Powertrain) or Radiator Cleaning (Charge Air Cooling) . Does the engine still overheat? |
- | Go to Step 9 | Go to Step 18 |
| 9 | Inspect the drive belt tensioner. Refer to Drive Belt Tensioner Diagnosis
for the 3.6L engine or Drive Belt Tensioner Diagnosis
for the 4.6L engine. Is the drive belt tensioner working properly and is the tension correct? |
- | Go to Step 11 | Go to Step 10 |
| 10 | Replace the drive belt tensioner. Refer to Water Pump and Generator Belt Tensioner Replacement
or Air Conditioning Compressor and Power Steering Pump Belt Tensioner Replacement
for the 3.6L engine or Drive Belt Tensioner Replacement - Generator
or Drive Belt Tensioner Replacement - Air Conditioning, Power Steering, and Water Pump
for the 4.6L engine. Does the engine still overheat? |
- | Go to Step 11 | Go to Step 18 |
| 11 | Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis . Does the thermostat operate properly? |
- | Go to Step 13 | Go to Step 12 |
| 12 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement (LH2) or Engine Coolant Thermostat Replacement (LY7) or Engine Coolant Thermostat Replacement (LC3) or Engine Coolant Thermostat Replacement (LY7, LLT) . Does the engine still overheat? |
- | Go to Step 13 | Go to Step 18 |
| 13 | Inspect for an inoperative after boil coolant pump if equipped. Does the engine still overheat? |
- | Go to Step 14 | Go to Step 18 |
| 14 | Inspect for an inoperative cooling fan. Refer to Cooling Fan Inoperative (V6) or Cooling Fan Inoperative (w/RPO LC3 or LH2) or Fan Clutch Diagnosis . Does the engine still overheat? |
- | Go to Step 15 | Go to Step 18 |
| 15 | Inspect for blocked cooling system passages. Are the cooling system passages blocked? |
- | Go to Step 16 | Go to Step 17 |
| 16 | Replace the radiator. Refer to Radiator Replacement (LY7 Standard Cooling) or Radiator Replacement (LH2 Heavy Duty Cooling) or Radiator Replacement (LH2 Standard Cooling) . Does the engine still overheat? |
- | Go to Step 17 | Go to Step 18 |
| 17 | Replace the engine water pump. Refer to Water Pump Replacement (LY7, LLT) or Water Pump Replacement (LC3) or Water Pump Replacement (LH2) . Did you complete the repair? |
- | Go to Step 18 | - |
| 18 | Operate the system in order to verify the repair. Did you correct the condition? |
- | System OK | Go to Step 2 |
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.