Thermostat

Thermostat

Component Test

A new thermostat should be installed only after the following tests and checks have been carried out:
- REFER to Diagnostic Routine A: Loss of Coolant Diagnostic Routine A, REFER to Diagnostic Routine B: The Engine Overheats Diagnostic Routine B, or REFER to Diagnostic Routine C: The Engine Does Not Reach Normal Operating Temperature Diagnostic Routine C
- Thermostat visual inspection

1. Remove the thermostat.

2. Examine the thermostat for signs of damage including:

- Valve not fully seated (light visible through the valve)
- Foreign material lodged in the main valve
- Bent or broken frame or flange
- Bent or broken valve or valve stem
- Wax leaking from wax reservoir or a bulge in the reservoir
- Any other damage or distortion

3. NOTE: If no damage is found during the inspection, do not attempt to open the thermostat using hot water or other heat sources. This method is not an accurate means to test the function of the thermostat and may damage the thermostat.
If damage is found during the inspection, remove any foreign material or broken pieces and install a new thermostat.

4. If no damage is found during the inspection, continue troubleshooting the system concern. REFER to Symptom Chart: Engine Cooling Symptom Related Diagnostic Procedures.