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Cooling System Thermostat Replacement: A Step-By-Step Procedure

cooling system thermostat replacement

This article provides you with a step-by-step procedure on cooling system thermostat replacement. The good news is that this replacement doesn't require advanced mechanical skill sets, and it's something that you can do by yourself without needing a professional.

Auto Repairs Are EXPENSIVE

The thermostat is a minor component of your vehicle's cooling system. However, this component plays a significant role, and when it's not working properly, it leads to major troubles in the cooling system. As a result, a faulty thermostat might easily lead to a complete engine failure.

Learning about cooling system thermostat replacement is essential, especially if you would like to save on labor costs. Since the replacement itself is not complicated and doesn't require a lot of mechanical skill sets, you can do it by yourself without needing a professional.

This article walks you through a step-by-step procedure on cooling system thermostat replacement. Once you follow this procedure, you don't have to worry about any mistakes that could get introduced to the cooling system, costing you thousands of dollars down the road.

What is the thermostat, and what does it do?

The thermostat is one of the many other components making up your cooling system. The thermostat controls the flow of coolant because it works depending on the temperature of the engine.

Since the engine operates within a specific temperature range, it needs coolant to run around it and bring it separately or down when the temperature exceeds a specific threshold. Thanks to the thermostat responsible for monitoring the engine temperature and allowing the coolant to flow when needed.

Think about the thermostat at a small valve that opens when the engine separator is very high and closes when the engine temperature drops to the required threshold.

Like any other component in your vehicle, the thermostat might get damaged or bad for various reasons. When the thermostat goes bad, it typically gets either stuck closed, or stock opened. When the thermostat gets stuck open, your engine won't reach the optimum operating level, but it's not a critical problem and would result in significant damages.

On the other hand, a stuck closed thermostat leads to significant engine problems because the engine will keep heating two crazy insane levels that might damage and seize the engine requiring installing a new engine.

Therefore, you must keep an eye on the thermostat and ensure it's working all the time properly. Whenever you notice any symptoms indicating a bad thermostat, you must replace it immediately if you want to deal with significant repair costs.

Symptoms of a bad thermostat

Before we dive into the details about “cooling system thermostat replacement,” it is important that you understand and confirm that your problem is coming from a bad thermostat. Luckily, when the thermostat goes bad, it shows some symptoms to bring your attention, including:

1.    High-temperature gauge readings

When the thermostat doesn't work properly, and when specifically, it gets stuck closed, you will immediately notice that the temperature gauge reading is very high. The temperature gauge is responsible for communicating with you by estimating the current engine temperature.

Keep in mind that the temperature gauge might read very high due to other problems related to the thermostat and could not. Therefore, you must monitor for other symptoms along with this one before you decide to replace your vehicle's thermostat.

2.    Erratic changes in the air temperature

If you're turning on the heating system, when the thermostat goes bad, you'll notice that the inside temperature of your vehicle increases significantly and probably decreases suddenly.

This sudden change in the air temperature within your vehicle might be linked to a faulty thermostat. Therefore, whenever you notice this, you must perform a thorough inspection and look at the thermostat before replacing it because the issue could also be related to a problem with the heating system itself.

3.    Coolant leaking underneath the vehicle

Since we indicated that the thermostat is responsible for allowing and preventing the coolant from flowing depending on your vehicle's engine temperature, you might deal with a coolant leak due to a faulty thermostat.

Therefore, take a closer look underneath your vehicle and watch for any fluid dripping. In some severe scenarios, you might even find a puddle of coolant sitting underneath the vehicle. You must distinguish between the different types of fluid inside your vehicle to determine whether the leak is coming from the coolant or not.

In some minor coolant leaks, you might not necessarily see fluid dripping or creating puddles. Instead, you will notice some residual coolant leak around the connections indicating that the coolant leaked first and then got evaporated because of the hot engine temperature.

Therefore, be thorough about your inspection to determine any internal or external coolant leak. The earlier you detect the problem, the easier it is to repair it and the lower repair costs.

4.    Weird noises

As a rule of thumb, whenever you notice any weird noises coming from the vehicle, you must never underestimate the issue because it might be linked to a significant internal problem.

Sometimes, the weird noises might be linked to a bad thermostat. For example, you might have problems with engine knocking, some boiling sound, or probably gurgling noises. All these symptoms and sounds might be linked to a bad thermostat, but they also can be linked to other troubles within your vehicle's cooling system.

Therefore, after you notice these sounds, you must continue inspections and have your mechanic confirmed the culprit before going ahead and replacing the thermostat. Yes, the thermostat replacement costs are not very high, but it's not worth your time and effort to replace a good component, whereas the issue comes from something else.

5.    Troubles with the heater performance

Finally, a bad thermostat impacts the behavior of your vehicle's heating system. Since the heating system relies heavily on the engine and the cooling system as a means to bring the excess temperature inside the vehicle when the thermostat goes bad and gets stuck open door stuck closed, the heating system might get impacted, and you'll notice that the inside temperature of your vehicle changes significantly as we indicated before.

Cooling system thermostat replacement

Would you confirm that the thermostat is the faulty component in your vehicle? You need to replace it immediately, especially if the thermostat gets stuck closed, preventing coolant from reaching the engine and cooling it down.

The good news is that replacing the thermostat is not a very complicated job, and it's one of those repairs that you can do at home without needing a professional. This way, you can save yourself a lot of money on labor costs if you compare the total cost to how much you'll pay when going to a dealership.

Keep in mind that if you decide to replace your vehicle's thermostat, do a thorough review of how the process is done. Most DIYs do not work the first time, and if your vehicle is expensive, you might want to leave it to professionals so you don't introduce damages by mistakes.

If you run it to replace your vehicle cooling system thermostat, follow these simple steps:

1.    Find the thermostat

The thermostat is typically located inside the upper radiator hose between the connection with the engine. If you have difficulties finding the thermostat, you can always refer to your vehicle's owner’s manual and get accurate guidance. You can also find any YouTube video specified for cooling system thermostat replacement for your vehicle's make, model, and year.

2.    Use a bucket to collect leaks

It is important to note that some coolant might drip on the floor when you replace the vehicle's thermostat. Since coolant contains some chemicals that can be toxic to the environment, you must have at least a 2-gallon container or bucket and place it underneath your working station to collect any coolant leaks.

3.    Take the clams out

Before you reach the thermostat, you'll have to remove the clamps connected to the radiator. Therefore, walk with your radiator hose until you reach the thermostat to take out any claims.

4.    Remove the hoses

Once getting to the thermostat, disconnect the hoses and allow any coolant leak to drop inside the container and reach the ground.

Disconnected the thermostat housing

The thermostat is typically sitting inside a specific housing that is bolted with specific bolts. Therefore, you will need to disconnect these bolts using any specific tool that helps you do the job.

5.    Compare the thermostats

Before you go ahead and install the new thermostat, you must perform a quick visual inspection to confirm that whatever you purchased matches the original thermostat. Unfortunately, many people installed the wrong thermostat and had to deal with major problems in their cooling system.

6.    Remove any gaskets

Depending on your vehicle's type, you might need to take out any gaskets around the hole where the thermostat is studying. Consider taking them out and placing them in a safe area so you can reconnect them when you're done.

Install the new thermostat

By now, you should be good to go with installing the new thermostat. However, you must monitor the direction of the old thermostat, so you don't place it in the wrong way. Typically, these prank sides of the thermostat should go down.

7.    Inspect the hoses and the clamps

It would be great if you took a closer look at the hoses and the clams and confirmed that they are in good condition. In some scenarios, you might even need to replace these two components as you're replacing the thermostat. Once you're done, you can reconnect them back.

8.    Check the coolant level

During the thermostat replacement, some coolant might drip underneath the vehicle, and some coolant might already leak before you even replace the thermostat. Therefore, a good tip here is to quickly check the coolant level and confirm it's at the right level. If it's below what's needed, you can always top it off with the required amount of coolant.

9.    Give your vehicle test drive

With that, you should be good to go! First, give your vehicle a quick test drive and see if you monitor any symptoms of a bad thermostat. If you're still dealing with problems, it might be worth reaching out to your mechanic now and checking with him about what was done wrong, so you don't have to deal with the thermostat problem again.


The thermostat plays a major role in your vehicle's cooling system. Therefore, this thermostat must be in good condition all the time to prevent dealing with engine overheating that requires significant repair costs.

When the thermostat goes bad, it must be replaced. Otherwise, you sacrificed the engine and might need to install a new one immediately. The good news is that cooling system thermostat replacement is not a very complicated job, and it's something that you can do by yourself.

This article provided you with a step-by-step procedure on replacing the thermostat and highlighted some tips to keep in mind during the thermostat replacement.

It is important to note that when the thermostat goes bad, it might already have your vehicle to deal with significant problems. When that happens, you need to evaluate whether it's worth spending the money performing repairs or not. For example, if you noticed that repair costs are approaching 75% or more from your vehicle's value, it is not worth their replacement, and instead, you should sell this vehicle and use its money to purchase a better car.

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