Updated at: 17-07-2022 - By: Lucas

What is the role of a car thermostat?

Temperatures in your car’s engine are between 91 and 104 degrees Celsius. A thermostat helps your engine perform in this range.

To summarize, the thermostat regulates the flow of coolant between the radiator and the engine by opening and shutting a valve in response to changes in temperature, in this case, the coolant temperature. For these reasons it is both compact and effective.

The thermostat’s container for the expanding element is directly in contact with the engine’s cooling fluid. Expanding liquid expands and forces a tiny rod that separates the center plate from its surrounding mounting base open, allowing coolant to flow through.

The tiny circuit is where the coolant flows after starting a cold engine. A valve restricts the flow of coolant to the primary radiator, causing the engine to heat up more quickly.

Upon reaching the predetermined temperature, the valve opens, allowing some antifreeze to be cooled from the main radiator. Over 90 degrees Celsius (191 degrees Fahrenheit) means that the valve is fully opened, allowing all of the antifreeze within to flow through the huge circuit.

There are just two indicators that can indicate a thermostat problem.

difficulties to warm up the engine, especially in the cold.

If the thermostat is always open in a wide or small circle, there are numerous possible outcomes. Overheating will occur, antifreeze will leak from the expansion tank, and the cooling system’s normal pressure will shift, among other things.

Where is the car thermostat located?

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To find out where your car’s thermostat is, all you need to do is consult the owner’s manual. Location of thermostat must be specified in cooling system section.

There is, however, a very universal search strategy that is applicable to most automobile models.

The radiator hose, which runs from the radiator to the engine, can be found by opening the hood and looking for the thickest pipe. A thermostat is attached to the other end of this conduit. Once you’ve reached the other end, locate the thermostat housing and remove it.

However, I still recommend that you first consult the user’s manual, and then use the procedure outlined above to search the database.

How to check the car thermostat without removing it?

Temperature readings can be easily checked by doing an on-the-spot diagnostic. If you want to do this, you’ll need a cold engine. The steps involved in the technique are as follows:

Start the engine and let it run for at least two to four minutes before shutting it off. Put your palm on the radiator’s top-most pipe. Since the coolant is only circulating through the heater and engine at this point, it should be chilly.

However, the presence of a hot pipe implies a thermostat problem. Check both the top and lower hoses when you’re doing a thorough inspection. It’s also a negative sign if they start to sweat.

Coolant might remain cold in lower branch pipes even after being heated. A lack of coolant in the radiator indicates that it is unable to dissipate heat. In both cases, we can talk about a thermostat malfunction, the needs to be removed and replaced with a new one.

In some cases, the valve gets stuck in an intermediate position. Here, it is neither closed nor open, so the engine warms up very slowly. As a result, your only option will be to remove the thermostat from the system.

Causes of a bad or failing thermostat

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1. The thermostat is stuck open

This is a more frequent occurrence. Thermostat valves in this configuration open all the way and stay open indefinitely. Because the spring is not strong enough, the valve does not return to its previous position. This is usually caused by corrosion, debris, or hardening of the liquid in the capsule.

Symptoms of a stuck open thermostat:

  • The engine takes much longer to reach the operating temperature, even in the warm season.
  • In cold weather, it does not fully warm up at all.
  • The heater either barely warms up or constantly blows cold air.
  • The engine power is reduced.
  • Fuel consumption increases.

Because of a stuck open car thermostat, the engine’s life expectancy is reduced over time.

2. The thermostat is stuck closed

This is perhaps the most dangerous thermostat malfunction. When the coolant remains in the small circuit, engine overheating is inevitable. This happens for several reasons, and among them are corrosion and debris.

Additionally, the liquid-filled capsule can lose its airtightness, rendering it ineffective. If you have this issue, it will not be possible to drive for long, and therefore it is very important to always remember how to identify it in a timely manner.

Symptoms of a stuck closed thermostat:

  • The arrow on the dashboard gauge goes off the scale.
  • If present, the corresponding warning errors will light up.
  • The motor can lose throttle response, stability, and it will even stall.
  • When the heater is running, you may feel the smell of antifreeze in the cabin.
  • White steam from under the hood can be present.

Overheating and engine failure are both possible if the thermostat is locked in the closed position, and you don’t address the issue quickly. Overall, it’s an unsafe situation.

Premature opening or closing

Temperatures at which the thermostat opens and closes are safe for the engine to operate. The coolant indicators are consistently outside of the ideal range if the valve is activated ahead of time.

An early opening or closing of the thermostat:

  • The engine does not warm up to operating temperature as expected.
  • The heater never heats up to maximum.
  • Fuel consumption is slightly increased.

It’s a minor inconvenience, but it’s not as serious as when the thermostat is stuck open or closed. The thermostat’s normal wear and tear is the most common cause of this problem.

Late opening or closing

Burnt coolant will be noticeable in the vehicle’s cabin if the engine frequently overheats. The causes of this error are the same. a result of regular use.

Using the improper thermostat can also be a factor in this problem. Due to the difficulty in locating a suitable replacement part for your vehicle, this occurs from time to time.

Incomplete opening or closing

This is a very rare occurrence. Only if the thermostat does not fully open is it dangerous. Engine overheating is a foregone conclusion if this continues. If the valve doesn’t fully close, it will be nearly identical to premature operation.


There are a lot of severe repercussions that can result from incorrect thermostat functioning, up to and including engine failure. These issues are more prevalent in the winter and summer months.

As a result, diagnosing a thermostat problem requires some knowledge and patience, or it may necessitate taking the vehicle to a repair facility that is authorized to do so.