Diagnosing a Bad Thermostat (Symptoms of a Bad Thermostat in a Car)

Last updated on November 22nd, 2021 at 09:00 pm

You find out the symptoms of a bad thermostat in a car. One of the most important devices in operating a car is the thermostat. It is responsible for regulating how the coolant flows when operating a car. The thermostat can either be in two phases which are “open” or ”close”. When you aren’t using your engine and it isn’t warm, the thermostat is closed but if it is running and gets to a particular temperature, it will be opened. The open phase is when the coolant will be able to flow to and from the radiator while it decreases the temperature. This flow makes sure your vehicle’s engine is working at its expected temperature.

If the thermostat develops a fault, there will be no way for the coolant to successfully circulate. It can either be in an open or close position. If the former occurs, coolant will flow constantly and the temperature will never reach its final level of heat. On the other hand, if the latter happens, the coolant won’t be able to pass through the radiator and finally through the engine. Either of these conditions is bad and could result in creating problems.

Diagnosing A Bad Thermostat: Symptoms of a bad thermostat in a car

Some of the symptoms of a bad thermostat in car you should watch out for to know whether your thermostat is bad are listed below:

Overheated Temperature Gauge

This should be the first thing you need to look out for. If your gauge is very high when you start to operate your car, then there is a problem with the thermostat.

Fluctuations in Temperature

When the vehicle’s temperature changes abruptly, something is wrong. It will be so low one second and just get abnormally high the next. This will make the engine perform poorly.

Leaks around thermostat

Another symptom will be if you notice that the coolant is leaking. You will mostly notice this near the housing of the thermostat. If the thermostat is in a closed position, it will start leaking on the floor under your vehicle.

How to test car thermostat without removing

To test your thermostat without removing it, follow the following tips;

Park your car and raise the hood. Then proceed to put the brake in an emergency. While the engine is warming up, watch the gauge closely. Within a few minutes, you would notice that the temperature increases as the engine is running. When the engine light comes on and the temperature is at the caution on your gauge, it is in the closed position. If the temperature starts rising and you can see that the top of your engine brings steam, then it is stuck closed.
Once the engine is cool, remove the radiator cap and start it again. Look into the opening of the radiator cap to observe the temperature gauge and coolant. The choke will open when the engine reaches its expected temperature, there will be a flow inside the radiator. That is proof that the thermostat is enabling circulation to take place. If the circulation isn’t flowing properly then something is wrong with the thermostat.
Raise the hood of your car and put the break-in emergency. If the temperature gauge is very hot and you hear any slamming or churning sound from the radiator tank, then that means your thermostat is opening and closing. It is letting coolant flow to and fro into the tank.
Start the vehicle’s engine so that it can warm up to its normal temperature. Then let the dashboard heater control be on its highest temperature with the fan at his full power. Wait for some minute so that the temperature will become normal. At this moment, you should be feeling the heat from the vents. The temperature must either be hot or slightly warm. However, after some minutes if the air is cool or warm and the gauge is below normal, then it is stuck open. This means the flow of the coolant is faster than normal. You need to get it replaced.

Driving with a thermostat stuck open

The car thermostat makes sure the temperature regulates properly without any hassle. If it isn’t opening or closing as it should, the car might start developing certain problems. However, it is actually preferable if it is stuck open then close. It isn’t advisable to drive with it stuck open. So, make sure you take it to a mechanic before it leads to damage.

If your thermostat is stuck open, it is running cool. This can cause fuel to condense on the cylinder. When this occurs, your car wouldn’t run on fuel as it should be. It makes it get a bad gas mileage.

Can a stuck open thermostat cause coolant loss

If you are driving and your temperature is stuck open, and then the temperature of the engine will drop then it should. It mostly occurs when the weather is very cold. A thermostat that is stuck open will cause a lack of heat and no coolant will be lost.

If the temperature is cool in your car, then your thermostat is in the open position. It doesn’t lose coolant; it actually makes the vehicle colder. A thermostat in a closed state will cause heat while the one in an opened position will cause cold. None of the conditions is preferable as they are both indicators that there is a problem with the cooling system.

Conclusion on Diagnosing a bad thermostat with Symptoms of a bad thermostat in the car

A thermostat is a cooling system in a car so it is very necessary that it works effectively. Your car stuck either in the open or close phase will cause discomfort to you, the driver, and your passengers. Always ensure that your vehicle is in good working condition, in order to make your driving experience pleasant and safe.

Jeffery Ekweghi

Hi dear, my name is Jeffery Ekweghi, and I am a certified mechanic and autobody parts technician. I created this site to share my expertise and experience with car lovers looking to resolve their car-related issues. I am certified in private cars and heavy-duty commercial vehicles. I have worked as a mechanic since 2015 and have experience in vehicle brands like Subaru, Jeep, Toyota, TATA, BMW, Mazda, Honda, Nissan, Kia, TVs, and Others; however, I primarily specialize in Toyota vehicles.