Much like a thermostat controls the temperature of your house, a car’s thermostat helps control your vehicle’s engine temperature. Without it, your vehicle may not warm up properly or will overheat. It’s an inexpensive part, but if it goes bad, it can create expensive problems for your car. 

A car’s thermostat is a spring-loaded valve that sits between the engine and the radiator. It’s closed when the engine is cold, allowing the car to warm up faster. Once the car reaches operating temperature, the thermostat opens and lets the coolant circulate through the radiator to cool down.   

When a thermostat goes bad, it will either stay open or closed. If it stays open, your car’s engine may not reach a normal operating temperature which will keep it from running efficiently. If the thermostat stays closed, the engine will overheat. 

Once a thermostat goes bad, there are some obvious signs it needs to be replaced:

On newer vehicles, the check engine light may come on if the vehicle doesn’t reach operating temperature. Likewise, the check engine light can come on when the temperature gets too hot. 

If the engine is running hot, one way to test for a bad thermostat is to place your hand on the top radiator hose. If it’s cool, but the engine is hot, it’s likely your thermostat needs to be replaced.

According to Repair Pal, the average cost to replace a thermostat is between $490 and $525. It could also be more or less depending on the make and model of the car. This cost reflects not only the part but the mechanic’s labor and the cost of coolant and other parts that need to be replaced. Keep in mind that the thermostat is more easily accessible on some cars than others, and the same goes for how easy it is to drain and refill a cooling system properly.

However, replacing your thermostat yourself could cost you less than $50, which covers the cost of the thermostat and coolant.

Absolutely! The thermostat is an easy part to replace. It sits near the top of the engine at the front of the car, so it’s easy to access. It doesn’t have any wires or electronic connections, so it’s an ideal repair for the novice mechanic.

The hardest part is draining the coolant from the radiator. This requires a bucket or drain pan and may require you to raise the front of the car on jack stands. This is also a good time to replace your antifreeze and flush your cooling system. 

Here’s a helpful tip: Save your antifreeze jugs to dispose of the old coolant. You will want to take the old coolant back to the auto parts store for proper disposal. 

First, you’ll need to gather the following parts and tools:

To change your thermostat, park your vehicle on a level surface, ideally in a garage or 

driveway. Then make sure your car’s engine is cool and perform the following steps in order:

Once you have filled the radiator with coolant, leave the radiator cap off and start the car. Let the engine run for about 10 minutes to warm up, checking the temperature gauge periodically. During this time, you will also need to check the coolant level in the radiator and top it off with coolant as needed.

After the car is warmed up and topped off with coolant, reinstall the radiator cap, and you’re good to go.