To determine if faulty thermostats are causing high engine coolant temperature, perform the
following:
1. Remove thermostat from the thermostat housing; refer to appropriate service manual,
cooling system chapter.
2. Inspect thermostat for correct operation; refer to appropriate service manual, cooling
system chapter.
[a] If thermostat opened at 97°C (207°F), check water pump; refer to section 13.8.
[b] If thermostat did not open at 97°C (207°F), refer to section 13.7.1.
13.7.1
Thermostat Replacement
Perform the following steps to replace thermostats:
1. Install new thermostat; refer to appropriate service manual, cooling system chapter.
2. Verify replaced thermostat; refer to section 13.7.1.1.
13.7.1.1
Test Engine with New Thermostat
Perform the following to determine if thermostat replacement resolved high engine coolant
temperature:
1. Start and run the engine.
2. Run the engine through its operating range with no-load for approximately 5 minutes,
allowing the engine coolant to reach normal operating range.
[a] If the engine coolant temperature is 88-96°C (190-210°F), no further troubleshooting
is required. Shut down the engine.
[b] If the engine coolant temperature is not 88-96°C (190-210°F), shut down the engine.
Check water pump; refer to section 13.8.
