DIY Subaru Thermostat Replacement: A Step-by-Step Guide to Saving Money and Improving Performance

As a Subaru owner, you know that regular maintenance is crucial for keeping your car running smoothly. One common issue that many owners face is a malfunctioning thermostat. The thermostat is responsible for regulating the temperature of your engine and ensuring that it runs at the optimal temperature. If your thermostat is faulty, it could lead to overheating and engine damage. In this article, we’ll show you how to change out the thermostat in your Subaru and save money on costly repairs down the road.

Why is it important to change the thermostat in a Subaru?

The thermostat in your Subaru is an essential component of your car’s cooling system. It regulates the flow of coolant to the engine to maintain a consistent operating temperature. A faulty thermostat can cause the engine to overheat, which can lead to serious engine damage. If you notice that your engine is running hot or your temperature gauge is fluctuating, it’s likely time to change out your thermostat. Regularly changing the thermostat can also prevent costly repairs down the line.

When to change the thermostat

Typically, the thermostat in your Subaru needs to be changed every 50,000-75,000 miles or when it begins to malfunction. Signs of a faulty thermostat include a fluctuating temperature gauge, a slow warm-up time, and a decrease in fuel efficiency. If you notice any of these symptoms, it’s time to change out your thermostat.

See also  How to Program Subaru Immobilizer Keys: A Comprehensive Guide for Car Owners and Mechanics

Tools needed for the job

Before you begin changing out your thermostat, you will need to gather a few tools. You’ll need a socket wrench set, a replacement thermostat, a gasket, and a container to catch any spilled coolant. It’s also a good idea to have a funnel to help refill the coolant after the job is completed.

Step-by-step instructions for changing the thermostat

  1. Begin by allowing your engine to cool down completely. This will prevent any burns from hot engine parts.
  2. Locate your thermostat housing. This is typically located on the engine block near the top radiator hose.
  3. Use your socket wrench set to remove the bolts that hold the thermostat housing in place.
  4. Carefully remove the housing and set it aside.
  5. Remove the old thermostat. Make sure to take note of its orientation so you can install the new one correctly.
  6. Clean the gasket surfaces on both the housing and engine block to ensure a tight seal.
  7. Install the new thermostat and gasket in the correct orientation.
  8. Reattach the housing using the bolts you removed in step three. Be sure not to overtighten the bolts.
  9. Refill the coolant using the funnel. Be sure to use the recommended type of coolant for your specific Subaru model.
  10. Start your engine and allow it to run for a few minutes to check for any leaks or issues.

Tips for troubleshooting common problems

If you encounter any issues during the thermostat replacement process, here are a few troubleshooting tips:

  • If you have trouble removing the bolts on the thermostat housing, try using a penetrating oil to help loosen them.
  • If the thermostat housing gasket is damaged during removal, replace it with a new one to ensure a tight seal.
  • If you notice coolant leaking after the replacement, make sure the housing bolts are tightened to the proper torque specification.
See also  Does Your Subaru Have Apple CarPlay? Find Out Now!


Q: Can I change out the thermostat myself?
A: Yes, with the right tools and instructions, changing out the thermostat in a Subaru is a relatively easy DIY job.

Q: How much will it cost to replace the thermostat in my Subaru?
A: The cost of a replacement thermostat varies depending on the make and model of your Subaru. Additionally, if you choose to have a mechanic replace the thermostat, the cost will likely be higher than if you do it yourself.

Q: Can a faulty thermostat cause engine damage?
A: Yes, a faulty thermostat can cause your engine to overheat, which can lead to serious engine damage if not addressed promptly.


Changing out the thermostat in your Subaru is a simple, yet crucial, component of routine maintenance. By following these step-by-step instructions, you’ll be able to save money and improve your car’s performance. Regularly changing out your thermostat can also prevent costly repairs down the line. So next time you notice your temperature gauge fluctuating, don’t hesitate to tackle the job yourself.

Avatar photo

Billy Covington

With a passion for all things automotive, Billy is our go-to expert on Subaru performance upgrades and modifications. He's been featured in several car magazines and blogs, and his extensive knowledge and expertise make him a valuable member of our team. When he's not working on cars, he enjoys playing guitar and writing music.

Recommended Articles