The car thermostat: what is it, what types are there and where is it

El car thermostat It is an essential piece that is part of your refrigeration system. Contrary to what some people think, its malfunction can lead to both overheating and the opposite, that the engine takes a long time to reach its optimum temperature with the consequent extra wear.

In this article we are going to explain in a clear and simple way everything you need to know about the thermostat: What is it y what is it for, where is it located, type what's up, how to replace it y how much new one.

What is it and what is it for

The car's thermostat is the part that opens and closes the coolant passage from the engine to the radiator. To understand its function you just have to have some very simple notions of mechanics. Without an effective method of cooling, a car engine would overheat to the point of failure.

For this reason, the engine of a car is traversed inside by a coolant that absorbs that extra unwanted heat and carries it to the radiator. The latter is nothing more than a fine grid inside which the liquid circulates and through which the air passes to cool it.

To this we must add that the engine works optimally at a certain temperature which is usually around 90º C. Until it reaches it, the radiator should not fulfill its function of cooling, since it would only increase the time it takes for the engine to reach that point.

That is where the thermostat kicks in, because when it detects that the engine is cold it cuts off the flow of coolant to the radiator so that it cannot cool down in it. When it detects that the engine has reached its optimum temperature, it opens the passage of the liquid so that the radiator can fulfill its function.

Where is a car thermostat located?

Every make and model is different, but in most cases you can find the thermostat by following the antifreeze hoses, which are the large tubes, usually black, that connect the engine with the radiator. To refine your search you can look at one of these two places:

• the first, on top of the engine near the Water Pump, which is responsible for circulating the liquid throughout the cooling system from the engine to the radiator and back
• the second, near lower engine hose to radiator, which can make access to it difficult.

Thermostat types

There are three types of thermostat for car, according to the method they use to detect the temperature and control the flow of the coolant. They are essentially the same as on most vehicles, so we can also say types of automotive thermostat:

electronic thermostat

These are the thermostats that are currently used and are controlled by the engine control unit. Since they require several connections and certain insulators, they are larger and cumbersome than the old ones. Despite this, the mechanism with which they open and close the duct remains practically the same in many cases. Only it is usually powered by a solenoid.

Being controlled by the engine control unit, the opening and closing of the thermostat can be managed based on more factors. Not only the temperature of the antifreeze on the thermostat itself.

Other sensors and thermometers distributed throughout the engine and its surrounding systems send the collected data to the control unit and it will open the thermostat as programmed. For example, a basic and essential management is through the coolant temperature sensor, which is usually found on the engine block. Another something more sophisticated is through the driving modes, which in cars with a very sporty approach, change the engine management in the most radical modes.

capsule thermostats

These thermostats were the most common a few decades ago. they worked without any electronics, only thanks to the dilatation properties of a wax that was encapsulated. When the temperature increased, the wax expanded and moved the gate that opened the duct. When it cooled down it contracted again closing the gate.

As you can understand, this only took into account the temperature of the antifreeze liquid when arriving at the thermostat itself. Something that severely limited temperature management, leaving the engine exposed to greater changes than with electronic thermostats.

bellows thermostats

Instead of being based on the expansion of a liquid, the operation of the bellows thermostat was based on the fact that alcohol is volatile. When the coolant heats up, the alcohol evaporates and expands the bellows to let the liquid through. By lowering the temperature, the alcohol returns to its liquid state and stops expanding the bellows.

This type of thermostat has the same problem as those with wax capsules: they only measured the temperature in the thermostat itself. with what the motor can suffer something more under certain weather conditions and/or use.

How to check if a car thermostat is malfunctioning

As you can already deduce after the explanation of what it is and what it is for, when the thermostat stops working, stop regulating the flow of coolant from engine to radiator. Therefore, essentially two things can happen:

let it stay open

When this happens, the symptom you will notice is that the engine takes a long time to reach optimum temperature. Something that increases wear and tear on the engine, which suffers more when running below the proper grades.

keep it closed

When this happens, the engine reaches its optimum temperature within a normal time frame, but it doesn't stop there. If the engine control unit has not detected the problem before, you will be able to see how the temperature exceeds the optimum point on the indicator on the dashboard, in addition to a warning light warning of a problem.

How to replace car thermostat

If you do not want this operation to be done in a workshop because you have knowledge of mechanics or you are a handyman, here we give you the basic notions to do it yourself. However, you should know that in most modern cars when something goes wrong and a warning light goes off, it is usually necessary to connect to the control unit once the part has been replaced to remove the warning.

Drain the cooling system circuit

For this step you will need a bucket to drain the liquid. Must loosen the hose at the bottom of the radiator to get all the coolant out.

Remove the faulty thermostat

Access to the thermostat, as we have told you before, it is usually in the upper part of the engine near the water pump or in the lower part of the engine in the coolant hose. The first thing you will have to do is disconnect the hoses that reach it. Then you must remove the hooks that fix it (they can be screws or fastening tabs) and remove the thermostat.

Install the new thermostat

Each car is different, so it is very important that you look at how the old thermostat was placed in order to correctly install the new one. Fix it with the screws or the fastening tabs.

Connect the hoses and fill with coolant

You have to re-close the circuit of the cooling system, so reconnect hoses, both those that went to the thermostat and the one that went to the radiator. Once you have made sure that they are well fixed, you must fill with coolant in the normal way and purge it.

How much does a car thermostat cost?

The price of this piece varies a lot from one brand to another. What is true is that electronic thermostats that current cars usually carry are more expensive than capsule thermostats old. Its price is usually between 25 and 50 euros for the former and between 5 and 12 for the latter.

We do not recommend that you buy a second hand thermostat, unless there are no stocks for your model. The good condition of this component is essential so that the engine does not suffer damage due to overheating. So buying a part whose condition is questionable can be dangerous for your car.