How can I replace a bad thermostat in my car?

The engine’s performance is dependent on the small and affordable car thermostat. This is because your engine will not function correctly if it fails, which could lead to more expensive engine work down the road. Fortunately, replacing a car thermostat is simple. In this article, I will guide you on how you can replace your car’s bad thermostat and the symptoms of a bad thermostat. You’ll also know the functions and cost of thermostat replacement.

how to replace car thermostat

What does my vehicle thermostat do?

The thermostat is a temperature-controlled valve that permits coolant to flow through part of or the whole coolant system. It has a simple design: it has a wax element that melts when temperatures reach a particular point, opening the valve, and the wax solidifies when the temperature drops.

Because the coolant is cold when you start your engine and the thermostat is closed, the coolant only circulates in the engine passageways. The coolant heats up when the engine warms up, and the thermostat opens. This permits the coolant to circulate back to the engine through the radiator. The thermostat and other cooling system components are broken out in detail here.

Therefore, the function of the thermostat in your car is to control the flow of coolant through the engine cooling system. With a thermostat, the coolant flow at normal temperature.

Read more:  Understanding automobile thermostat

What are the symptoms that indicate my car thermostat is bad?

The thermostat in your automobile, truck, utility vehicle, or van is in charge of releasing coolant into the engine when it becomes too hot. This temperature gauge can fail after 10 years or even less, so if you drive an older car, it’s a good idea to be aware of the warning signals that the thermostat is failing. These warning indicators are listed below by Accurate Auto.

  • Old temperature gauge readings
  • Air temperature changes
  • Coolant leaks
  • Strange sounds
  • Heater problems

Old temperature gauge readings

When you first start your car, the temperature gauge should read cold and gradually rise to normal as the engine warms up. It’s conceivable that there’s an issue with the thermostat if the temperature gauge is reading lower or higher than normal. If your automobile is constantly overheating, the thermostat is most likely not flowing coolant into the engine to lower the temperature.

Air temperature changes

The temperature of the air that flows into your vehicle through the vents can also be affected by the thermostat. It’s a clue that your thermostat isn’t working properly if the air temperature changes from hot to cold or cold to hot. These temperature variations are frequently irregular and abrupt. When you notice these interior temperature changes, it’s critical to have your car evaluated.

Coolant leaks

When a thermostat malfunctions, it frequently remains in the closed position. Coolant will overflow from the thermostat housing when the engine overheats. This means that coolant seeping from your engine could indicate a problem with your thermostat. It could also indicate that your radiator hoses, the radiator itself, or the seals and gaskets are faulty.

Strange sounds

Strange noises are another indicator that your thermostat is failing. Because the coolant is boiling, you may hear rumbling sounds coming from the engine. These sounds could be coming from the radiator. It could also sound like something is cooking or knocking. The sound can also be bubbling at times. All of these indicators lead to a cooling system issue.

Heater problems

Finally, no matter how much you turn up the heater in your car, you won’t have hot air rushing through the vents if your thermostat is stuck in the open position. Because we’re swiftly approaching summer, you may not notice this problem right now, but if you had problems with your heater last winter, bring your vehicle into our shop for an inspection.

Read more: Understanding Cooling System Hoses

What is the step-by-step guide I can use to replace my car thermostat?

The followings are the common ways you can replace a car thermostat:

  • Locate your thermostat
  • Place a bucket beneath it
  • Remove the clamps
  • Pull off the hose
  • Remove the bolts that hold the thermostat housing
  • Lay the new gasket in place
  • Keep the new thermostat close
  • Replace the hose and clamps
  • Replace the fluid

Now let’s have a thorough explanation!

If you’ve not done so, locate your thermostat. These procedures are for thermostats that are positioned where the top radiator hose connects to the engine. The approach is the same if your thermostat is in the bottom radiator pipe.

Place a bucket beneath the area where you’ll be working. Some fluid will leak out, so keep a clean two-gallon container on standby to capture it and restore it to the radiator when you’re done. Take the clamp off. Locate your thermostat by following the radiator hose.

Remove the hose. Some fluid will escape and drain into your bucket at this point.

Remove the bolts that hold the old thermostat in place and lift it out. Compare the old and new thermostats and their gaskets. If the new thermostat and the gasket that comes with it aren’t the same as the old ones, return to the store and purchase the correct ones.

Place the new gasket on top of the old one. There’s a gasket around the hole where the thermostat used to be, so remove it as well. Scrape away any trapped gasket parts, but don’t allow them to fall into the hole.

Drop-in and put the new thermostat in place. Make sure the spring is facing down before replacing the bolts.

The hose and hose clamp should be replaced. If your hose clamp has screws, tighten them down but not so tight that they cut into the hose.

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Pour any fluid that has leaked from the hose back into the radiator fill hole or coolant reservoir from the container. Make sure not to spill it on the ground, where it could endanger children and animals. If you spill any, clean it up completely before hosing it down and putting the rags in a sealed plastic bag before throwing them away.


Read more: Understanding Automobile Radiators


Watch the video below to see how you can replace a car thermostat:

How much does it cost to replace my car thermostat?

The good news for individuals who have a broken thermostat is that it is rather inexpensive to replace it. The exact cost will, of course, be determined by the type and model of your vehicle. For the ordinary auto owner, however, a skilled mechanic may expect to charge between $140 – $300 to repair the thermostat in their vehicle.

The actual thermostat unit costs from $20 – $80, however, it can cost more in high-end or sports cars. The labor cost will be between $120 and $220. (Possibly more if going to a dealership).

Keep in mind that most mechanics charge between $80 – $110 per hour for their work. A mechanic should be able to finish the thermostat replacement in 1 to 2 hours. As a result, you end up paying more for labor than you do for the thermostat itself.

Many car owners attempt to save money by replacing the thermostat on their own. Unless you have prior expertise working on automobiles, your vehicle’s thermostat is in a convenient location, and you have a good repair manual to guide you, you should hire a professional to replace it.

Read more:  Understanding Radiator Pressure Cap


Yes, it is obvious the functionality of a thermostat in an automobile cannot be overlooked. As a car owner or driver, you are expected to have some basic knowledge about your car thermostat; when they developed faults and need replacement, and to replace them and some common symptoms to show that. That’s why this article is for you.

I hope you learn a lot from this article, if so, kindly share it with others. Thanks for reading, see you around!