For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you review the Symptoms-Engine Cooling Diagnosis information and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling
2 | Verify that the engine does not reach normal operating temperature. Does the engine reach normal operating temperature? | System OK | Go to Step 3
3 | Inspect the coolant level. Is the coolant level below the add mark? | Go to Step 4 | Go to Step 5
4 |

1. Add coolant as necessary. Refer to Cooling System Draining and Filling .
2. Perform a cooling system pressure test.

Is the repair complete?

System OK

Go to Step 5

5 | Inspect for a stuck open, missing, or wrong type of thermostat. Refer to Thermostat Diagnosis . Is the thermostat operating properly? | System OK | Go to Step 6
6 | Install the correct replacement thermostat . Refer to one of the following procedures:

• | Engine Coolant Thermostat Replacement for 8.1L

• | Caterpillar® 3126 Unit Repair Manual

Is the repair complete?

System OK

Go to Step 7

7 | Run the engine in order to verify the repair. Does the engine fail to reach normal operating temperature? | Go to Step 1 | System OK