Cooling System Diagnostic System Check Cooling System Testing
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
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Caution: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if radiator cap or surge tank cap is removed while the engine and radiator are still hot. Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the cap. | ||||
1 | Does the engine appear to be overheating, with or without loss of coolant? | -- | Go to Fan Clutch Diagnosis | |
2 | Is a loss of coolant evident? | -- | Go to Loss of Coolant | |
3 | Does the engine fail to reach the normal operating temperature? | -- | ||
4 | With the engine running and warm with the radiator filler cap off, verify that the coolant is circulating in the radiator. Is the coolant circulating? | -- | ||
5 | Feel around the front of the radiator core. Cold spots mean a blockage. Are there cold spots? | -- | ||
6 | Remove the coolant outlet. Refer to Engine Coolant Thermostat Replacement . Is the thermostat stuck closed or is the coolant outlet blocked? | -- | ||
7 |
Is the system OK now? | -- | System OK | |
8 | Install new parts as necessary. Is the system OK now? | -- | System OK | |
9 | Inspect the crossover passage at the front of the inlet manifold (the thermostat must be removed for access). Is this area clear? | -- | ||
10 |
Is there a blockage? | -- | ||
11 |
Does the cylinder head(s) require further inspection? | -- | ||
12 | Use a penlight to inspect the engine block for a clogged coolant passage. Has a blockage been found? | -- | ||
Water Pump Test
- Bring the engine up to normal operating temperature.
- Squeeze the (upper) radiator inlet hose, while accelerating the engine speed. You should feel a pressure surge.
- Inspect for a plugged vent hole in the water pump.
Radiator Test
- Bring the engine up to normal operating temperature.
- Turn the engine OFF.
- Cold spots indicate there are clogged sections of the radiator core.
| • | The radiator should feel hot along the left side. |
| • | The radiator should feel warm along the right side. |
| • | There should be an even temperature rise from the right to the left. |
Cooling System Diagnostic System Check Exhaust Leaks and Noise
Exhaust Leaks
- Drain only enough coolant so that the level is just above the top of the cylinder head. Refer to Cooling System Draining and Filling .
- Disconnect the radiator inlet (upper) hose.
- Remove the coolant thermostat. Refer to Engine Coolant Thermostat Replacement .
- Remove the accessory drive belt. Refer to Drive Belt Replacement in Engine Mechanical-2.2L or Drive Belt Replacement in Engine Mechanical-4.3L.
- Start the engine. Increase the engine speed (RPM) several times, while observing the coolant level. Any noticeable rise in the coolant level or the appearance of bubbles may show that exhaust gas is leaking into the cooling system.
Notice: Allowing the drive belt tensioner to snap into the free position may result in damage to the tensioner.
Noise
Cooling system noise can be caused by restrictions to coolant flow. This can cause the coolant to boil at some localized point. Symptoms usually appear after extended idling or driving.
- Inspect for the following possible symptoms:
- Backflush the cooling system, then retest. Refer to Flushing .
- Use a mechanic's stethoscope to determine what areas are still affected.
- Disassemble the suspect components for further inspection and cleaning, as necessary. Refer to Cooling System Diagnostic System Check in order to locate restrictions in the cooling system.
| • | The engine may produce snapping or cracking noises. |
| • | The radiator hoses may expand or collapse. |
| • | The coolant heater hoses may vibrate or thump. |
| • | The coolant heater core may gurgle or surge. |
| • | The engine overheat lamp may or may not be illuminated. |
