For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Check the level of the coolant in the coolant recovery reservoir. Is the coolant in the reservoir at the proper level? | -- | Go to Step 3 | Go to Step 2
2 | Add engine coolant as necessary. Refer to Cooling System Draining and Filling . Does the engine still fail to reach normal operating temperature? | -- | Go to Step 3 | System OK
3 | Check if the thermostat bypass valve is stuck open. Is the thermostat bypass valve stuck in the open position? | -- | Go to Step 4 | Go to Step 5
4 | If necessary replace the bypass valve. Does the engine still fail to reach normal operating temperature? | -- | Go to Step 5 | System OK
5 | Check to see if the correct type of thermostat was installed, or if the thermostat sticks (or is stuck) in the open position. Refer to Thermostat Diagnosis . Was the incorrect thermostat installed or does the thermostat stick, or is the thermostat stuck, in the open position? | -- | Go to Step 6 | System OK
6 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement . Does the engine still fail to reach normal operating temperature? | -- | -- | System OK