Why is My Car Overheating with a New Thermostat

The engine of a car consists of many different components, each with its function and directions to use. Every engine needs a thermostat to function properly. The thermostat has to function properly as well.

An overheating car might be caused by a faulty thermostat but what causes a car to overheat even with a new thermostat? Why is my car overheating with a new thermostat?

The reason why your car is still overheating with a new thermostat could be because of a damaged radiator, faulty water pump, clog in the heater core, contaminated coolant, etc.

Functions of Thermostat in a Car?

Every car has a thermostat installed in the engine. The function of a thermostat in a car is the control of hot water flowing through the radiator. You will always see the thermostat placed on the engine block, regulating the flow of the coolant for the radiator.

The major function of the thermostat in a car is to maintain the minimum working temperature in the engine. When you switch on your car, the coolant and the antifreeze are enclosed by the thermostat in the engine.

When a particular temperature is reached, it opens. This allows the coolant to flow through the radiator and helps keep the engine at a specified temperature.

To elaborate, a thermostat is a regulator of temperature in any engine. Thermostats perform the role of regulating the appropriate amount of coolant that flows through the radiator to maintain a specified temperature.

Thermostats work in a very simple way; they allow or restrict coolant flow to the radiator depending on the temperature.

Why Is My Car Overheating with a New Thermostat?

These are the underlying issues that make your car overheat with a new thermostat:

1. Damaged Radiator

A radiator is a heat exchanger that cools an internal combustion engine. It helps in eliminating surplus heat from the engine.

The coolant in your car’s engine passes through the radiator. If the radiator is broken or damaged, the coolant will be lost along the process and overheating is bound to occur.

2. Faulty Water Pump

Water in the radiator flows from the water pump, which works in synergy with the belt. When the water pump gets faulty, the end result is overheating.

3. Clog in Heater Core

A clog (obstruction or blockage) will affect the free flow of coolants in the heater core.

4. Contaminated Coolant

Using or adding a contaminated coolant such as having oil in your coolant could cause all kinds of problems to your engine no matter the level of the fluid.

5. Damaged Head Gasket

As you probably know already, the head gasket provides the seal between cylinder heads and the engine blocks. It is also responsible for the flow of coolant into the engine.

If the head gasket gets damaged, the coolant will leak and that will result in damage to the engine.

6. Inappropriate Thermostat Installation

If your car overheats even when you have installed a new thermometer in it, it could be that the thermostat was installed inappropriately.

When your car overheats, it could mean a lot of things. A car overheating with a new thermostat could be caused by many problems.

It could be a faulty water pump, a damaged radiator, a clog in the heater core and radiator, or one of both. It could also be a coolant-related problem.

It is important that you do not drive your car under such circumstances though. If you drive an overheating car, you risk getting your car damaged severely. Try to get it solved with the help of a specialist.

What Happens When Car Overheats with New Thermostat?

Whenever you observe that your car is overheating even when you have a new thermostat installed in it, you will come across some signs as well:

  • Fluctuating Temperature Readings: A bad thermostat will definitely cause the system to misread the temperature. As a result, there will be an erratic change in temperature. Sometimes, it will read at a very high temperature. It is possible that the thermostat is still not working properly because a faulty thermostat will block the coolant flows into the radiator thus causing overheating.
  • Unusual Engine Noise: When your car overheats, one thing that will definitely happen is the production of rumbling sounds from your car’s engine. All kinds o sounds like gurgling, knocking, or rustling sounds. These sounds are very uncomfortable and you will need to see a mechanic ASAP
  • Inefficient Engine: Whenever you notice that your car is performing at a significantly lower level than it works normally, it could be caused by overheating. Ensure you get your thermostat checked to be sure it is working properly.

What to Do When a Car Is Still Overheating with New Thermostat?

  • The first thing you should do when your car overheats with a new thermostat is not to drive the car. That could be very disastrous in the long run and harmful to your car.
  • You can also check the engine yourself to see if you notice any abnormalities in the engine.
  • If you’ve checked it yourself and you could not find a solution to the overheating car, you need to take your car to a mechanic or diagnosis and repairs

How Long Does It Take for a New Thermostat to Work?

Replacing a thermostat usually takes about 1 – 2 hours. Afterward, the new thermostat can take up to an hour to start functioning optimally.

Oftentimes, it is difficult to hear when a thermostat in an engine is working. It is easy to not notice when it is in operation except if you listen to it carefully.

Moreover, the installation of a new thermostat should be done by a technician. The technician has the necessary skills and expertise to replace the thermostat.


An overheating car with a new thermostat shows that there are underlying problems in the radiator or cooling system. It is expedient for you to take your car to a professional to analyze and repair it properly.