Why do thermostats fail

The components inside the thermostat are only designed to handle normal operating temperatures, and severe overheating may damage said components.

Just as with any automotive fluid, over time the coolant can become contaminated and start failing. A common problem is the congealing of the coolant into a thick sludge-like material. This sludge can get inside the thermostat and cause the flow to be restricted or even cut-off altogether.

The sludge also prevents the thermostat from taking accurate readings, causing delay in opening or closing, which leads to over-cooling or overheating.

Just as most automotive parts, the thermostat is mass produced in a factory. Before a thermostat is released for sale, it is inspected for proper operation. The human element plays a large part in the role of inspecting the thermostats and some problems are missed. These minor defects can lead to a thermostat being defective straight from the box, or failing shortly after installation.

Age is another common reason for failure. Pricing and availability is subject to change. Ownership thermostats. View More. Thank You Thanks for subscribing. Check your in-box to get started. Sign Up More Info. We notice you're using an ad blocker.

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The exact text will differ depending on the actual application you have running. Refresh the Autoblog page you were viewing. Hey again! You still haven't turned off your adblocker or allowed our site. One sign that you might have a stuck-closed thermostat is rapid temperature increase during normal operation. If overheating is indicated on your dash, do not delay in getting it checked out and repaired. Another symptom may be leaks near the thermostat housing. When blocked, the pressure can rupture gaskets and compromise weaker parts of the system at connections.

Problems with heat in the passenger compartment might indicate a stuck-open condition; the interior heat depends on hot coolant circulating through the heater core. Unusual temperature fluctuations noted on the gauge are also a sign of a failing thermostat. If you suspect a faulty thermostat, run a few checks. With the engine cold, remove the radiator cap and start the engine. Replace the radiator cap and turn off the engine.

Check the radiator hoses for differences in temperature. If one usually the top is cooler, but the bottom is burning up, that indicates the thermostat is stuck closed as well.

Do not stick your hand near the front of the engine while the fan and belt are moving, and never remove the radiator cap from a hot engine. The final test involves removing the thermostat and doing a temperature test.