MBE 900 DDEC VI Troubleshooting – Section 16.1 Faulty Thermostats

Section 16.1
Faulty Thermostats

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

1. Remove thermostat from the thermostat housing; refer to MBE 900 Service Manual (6SE9007), cooling system chapter.
2. Inspect thermostat for correct operation; refer to MBE 900 Service Manual (6SE9007), cooling system chapter.
   1. If the thermostat is fully open at 95°C (203°F), check insufficient radiator air circulation; refer to "16.2 Insufficient Radiator Air Circulation" .
   2. If the thermostat is not fully open at 95°C (203°F), refer to "16.1.1 Thermostat Replacement" .

Section 16.1.1
Thermostat Replacement

Perform the following steps to replace thermostats:‪

1. Install new thermostat; refer to MBE 900 Service Manual (6SE9007), cooling system chapter.
2. Verify replaced thermostat; refer to "16.1.1.1 Test Engine with New Thermostat" .

Section 16.1.1.1
Test Engine with New Thermostat

Perform the following steps to determine if thermostat replacement resolved low engine coolant temperature:‪

PERSONAL INJURY ‪
To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.‪

1. Start and run the engine.
2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
   1. If the engine coolant temperature is 70-95°C (158-203°F), no further troubleshooting is required. Shut down the engine.
   2. If the engine coolant temperature is not 70-95°C (158-203°F), shut down the engine. Check insufficient radiator air circulation; refer to "16.2 Insufficient Radiator Air Circulation" .