For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Check the level of the coolant in the coolant recovery reservoir or the surge tank. 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. 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.

• | For the L36 & L67 engine, refer to Engine Coolant Thermostat Replacement .

• | For the L47 engine, refer to Engine Coolant Thermostat Replacement .

Does the engine still fail to reach normal operating temperature?

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System OK