For 1990-2009 cars

Verify that overheating is not caused by the following conditions:

1. While pulling a trailer that is within the recommended towing weight.
2. After prolonged idle in gear, with the A/C system operating.
3. After prolonged driving in slow city traffic, traffic jams, parades, etc.

If these conditions can be eliminated as the cause of overheating, refer to the table below.

1. Verify that the cooling system is properly filled.
2. If the complaint is a low temperature gauge reading, check the temperature gauge for proper operation. Connect a Scan Tool to the vehicle and read the system temperature.
3. Compare this reading to the temperature gauge.
4. Replace the gauge or switch if necessary.
5. If the complaint is no heat from the HVAC system. Verify the proper operation of the thermostat. Refer to Thermostat Diagnosis .

### Possible Causes

Possible Cause | Correction
--- | ---
Coolant fan inoperative | Refer to Low Engine Coolant Indicator Always On .
Thermostat stuck closed | Replace the thermostat
Radiator fins obstructed | Remove or relocate add-on parts that block air to the radiator. Clean away bugs, leaves, etc. In cold climates, clear away snow, etc. from the radiator core.
Surge tank outlet hose pinched or kinked (at radiator) | Relieve kinks by re-routing. Replace the hose if necessary.
Incorrect radiator | Check the radiator usage chart in a parts catalog. If needed, replace with the correct radiator.
Loss of system pressure | Pressure check system and surge tank cap. Ensure the correct cap is being used.
Damaged or missing air seals or deflector | Repair or replace as required.
Malfunctioning coolant pump | Replace the coolant pump.
Air trapped in cooling system | refill the cooling system