Thermostat stuck closed

The thermostat, when closed, keeps the coolant in the engine until it reaches a certain temperature. If the thermostat is stuck closed, the coolant will remain in the engine rather than circulate to the radiator where it cools. This can lead to overheating as the heat from the engine will not dissipate.

Table of Contents

• 1. Symptoms
  • 1.1 Heater Blows Cold Air Always
  • 1.2 Engine Overheats

Symptoms

Heater Blows Cold Air Always

If the heater is always blowing warm air, the thermostat may be stuck closed. If the coolant cannot circulate out of the engine, it cannot reach the heater core. This will prevent the air from being heated prior to entering the passenger compartment.

Engine Overheats

If the engine routinely overheats, the thermostat may be stuck closed. The coolant will remain in the engine and will continue to heat without being cooled.