Series 50 – Section 27.7 Faulty Thermostats

Section 27.7
Faulty Thermostats

To determine if faulty thermostats are causing high engine coolant temperature, perform the following:‪

1. Remove thermostat from the thermostat housing; refer to "4.3.2 Draining and Removal of Thermostat" .
2. Inspect thermostat for correct operation; refer to "4.3.2.1 Inspection of Thermostat" .
   1. If thermostat opened at 97°C (207°F), check water pump; refer to "27.8 Faulty Water Pump" .
   2. If thermostat did not open at 97°C (207°F), refer to "27.7.1 Thermostat Replacement" .

Section 27.7.1
Thermostat Replacement

Perform the following steps to replace thermostats:‪

1. Install new thermostat; refer to "4.3.4 Installation of Thermostat and Seal" .
2. Verify replaced thermostat; refer to "27.7.1.1 Test Engine with New Thermostat" .

Section 27.7.1.1
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.
   1. If the engine coolant temperature is 88-96°C (190-210°F), no further troubleshooting is required. Shut the engine down.
   2. If the engine coolant temperature is not 88-96°C (190-210°F), shut the engine down. Check water pump; refer to "27.8 Faulty Water Pump" .