[CAUTION! NEVER NEVER NEVER attempt to open the radiator cap, engine coolant reservoir cap, or remove any part of the engine coolant system until the engine has cooled to a safe temperature! Opening any part of a hot engine coolant system is an EXTREME BURN HAZARD and can result in severe scalding!]




Car thermostat problems are rare. When a car thermostat problem does show up it’s probably one of two things. Left unrepaired, either will cost you money. . .

Your thermostat can stick shut, in which case the ‘Engine Temp’ light should come on or a high temperature will show on your engine temperature gauge.

A high temperature indication doesn’t necessarily mean a stuck thermostat, it could be a loss of engine coolant. In either case you should shut off your engine and get to the source of the problem before driving further.

Driving an overheating engine can quickly lead to a major engine rebuild costing several thousand dollars.

A thermostat can also stick open, but most cars don’t have a ‘Low Engine Temp’ light and most people don’t worry about a cool engine temperature. But a thermostat that’s stuck open costs you money every mile you drive.

A 195-degree thermostat that sticks open and reduces the engine coolant temperature to, say, 160 degrees, will allow fuel to condense on the cylinders due to cooler water jacket temperatures. Condensed fuel doesn’t burn properly and you pay a mileage penalty.

According to the "How to Fight High Gas Prices" Maintenance Tips article at, a thermostat that’s stuck open can create a 7% mileage penalty that equates to paying over $.17 extra for gas priced at $2.50/gallon.

If you have a water temperature gauge, the temperature difference is easy to see. But if you only have a high temperature warning light, you may not notice the slight increase in fuel consumption unless you’re really tracking your fuel economy closely.

Thermostats are usually dependable so, if you only have warning lights, you probably shouldn't install a new engine thermostat ‘just in case’. The approximate cost to replace a car thermostat by a paid mechanic can be over a hundred dollars, even though the part costs only about ten.



The How Stuff Works Car Cooling System pages detail all aspects of engine cooling systems.

And the Wikipedia Thermostat Page discusses number of different type of thermostats and explains how automobile thermostats work.



You can quickly locate the engine thermostat you need for your car with this easy to use Amazon Search Tool. When you click a thermostat, Amazon will ask you for the info they need to find the right product for your car:

Engine thermostats are also available at local auto parts stores. A number of them let you check availability, place your order online, and pick up at the store.

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