Engine Coolant Thermostat: Description

A pellet-type thermostat controls the operating temperature of the engine by controlling the amount of coolant flow to the radiator. The thermostat is opened when the engine temperature reaches 195°F (90°C). When opened, the thermostat allows engine coolant to flow to the radiator. This provides quick engine warm up and overall temperature control.

Fig 1: Identifying Engine Coolant Thermostat

Courtesy of DAIMLERCHRYSLER CORP.

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 the engine without a thermostat can cause the following problems:

• Longer engine warm-up time
• Unreliable warm-up performance
• Increased exhaust emissions
• Crankcase condensation

This condensation can result in sludge formation.