For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
1 | Check the coolant level in the radiator surge tank. Is the coolant at the proper level? | Go to Step 3 | Go to Step 2
2 | Add coolant to the radiator surge tank as necessary. Does the engine still fail to reach normal operating temperatures? | Go to Step 3 | System OK
3 | Check for a blockage in the coolant passages. Are there any blockages in the coolant passages? | Go to Step 4 | Go to Step 5
4 | Flush the cooling system or flow check the radiator. Does the engine still fail to reach normal operating temperatures? | Go to Step 5 | System OK
5 | Check to see if the incorrect thermostat was installed or if it is stuck or sticks in the open position. Was the incorrect thermostat installed, or is it stuck or does it stick in the open position? | Go to Step 6 | --
6 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement. Does the engine still fail to reach normal operating temperature? | -- | System OK