The thermostat is what regulates the flow of coolant through the engine.

When the engine has been sitting for a while and is not warm, the thermostats will be closed.

When the engine reaches its operating temperatures, a sensor inside the thermostat causes it to open. This allows coolant to flow to and from the radiator. As a result, decreasing the temperature so it can be recirculated through the engine. This constant flow is what keeps your vehicle’s engine functioning at the optimum temperature.

Thermostats perform three major functions:

  1. Help an engine to reach operating temperature more quickly
  2. Help regulate engine temperature to prevent overheat
  3. Restrict flow to promote more even cooling

A bad thermostat will prevent the engine from operating within its ideal temperature range.

For example:

  • A thermostat stuck in the open position will cause a continuous flow of coolant, resulting in a lower operating temperature.
  • A thermostat stuck in the closed position will prevent coolant flow, causing the temperature to steadily rise.

Either way, this will cause damage to your engine.

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Signs of a Bad Thermostat

Temperature gauge reading very high and engine overheating

  • The first and potentially most alarming symptom will be the temperature gauge reading high into the red. This is often the very first sign that the thermostat is not functioning properly.

Temperature changing erratically

  • Erratic temperature fluctuations can also occur causing dramatic spikes and drops in temperature which eventually leads to poor engine performance. As a result, You may see the temperature very low at one point and climb to a very high level the next.

Coolant leaks around the thermostat housing or under the vehicle

  • This can be noticeable in a variety of locations, but most commonly around the thermostat housing. This can eventually cause other coolant hoses to leak as well resulting in coolant often times leaking on the ground under your vehicle.

Whatever the cause, it’s a good idea to start looking into the problem before it’s too late.