Section 356 (Engine Cooling System - 2500 Hd & 3500 Hd): Engine: Thermostat: Description: Diesel
Thermostats for the 6.7L Cummins diesel, while physically interchangeable, should not be mixed and matched. For model year 2013, the 6.7L diesel engine uses a 190° Fahrenheit thermostat. Confirm the temperature stamp on the thermostat rim prior to removal or installation.
Do not operate the engine without a thermostat, except for servicing or testing.
The 6.7L diesel engines use a pellet-type thermostat that controls the operating temperature of the engine by controlling the amount of coolant flow to the radiator. On all engines the thermostat is closed below Above this temperature, coolant is allowed to flow to the radiator. This provides quick engine warm up and overall temperature control.
Coolant leakage into the pellet container will cause the thermostat to fail in the open position. Thermostats very rarely stick. Do not attempt to free a thermostat with a prying device.
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes other problems. These are: longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase condensation. This condensation can result in sludge formation.