Can You Drive A Car Without A Thermostat? (+Effects Explained)

Owning a car comes with all kinds of questions and we’ve answered both obvious questions like if you can drive your car without brakes and less obvious questions like can you drive it without a muffler.

But the questions never end and you may have some that are related to the thermostat of a car. For example, if you notice your thermostat has gone bad but still need to use the car, what kind of consequences can this have?

Here’s the quick answer:

Driving without a thermostat isn’t advised. The thermostat allows your engine to reach optimal operating temperature. Its removal can lead to inefficient fuel combustion, decreased performance, increased emissions, and poor fuel economy. Additionally, cooler engine temperatures can cause increased wear due to ineffective lubrication. Despite short distance driving being possible, it’s harmful long-term.

However, this certainly doesn’t answer the question entirely. In the article below, we’ll first have to look at the thermostat and its function and location in the car. Furthermore, we’ll discuss the effects of running without a thermostat for extended periods and how long this would be possible. Other related questions are also answered. Read on!

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How Does A Thermostat Work And Where Is It Located?

Thermostats are an integral part of the cooling system of your car. These small devices are only about 2 inches in diameter, but they’re almost single-handedly responsible for regulating the amount of coolant that flows from the radiator to the engine. In the image below, you can see what this little device looks like.

To understand how the thermostat works, you need to understand the cooling system of a car. Don’t worry; we’ll keep it to the point. First, you fill your car up with coolant in the coolant reservoir. When the engine gets hot, coolant starts flowing from the reservoir to the radiator, which is then directed to the engine. However, before it reaches the engine block, it encounters the thermostat.

When the engine needs a lot of cooling, the thermostat will open all the way to make sure as much coolant as possible reaches the engine (around 200 degrees Fahrenheit). However, if only a little coolant is needed, the thermostat only opens slightly.

Thermostats open and close automatically because of their simple design. They have a rod connected to the center of a valve filled with wax. This wax starts melting and expanding at approximately 180 degrees Fahrenheit. When the wax expands, it pushes the rod up, opening the thermostat and allowing coolant to flow through. In essence, the thermostat is the gatekeeper and ensures the engine isn’t too warm or too cold.

Finally, it’s good to know that the thermostat is located between the radiator and the engine. If you’re in the process of replacing this thermostat or need to remove it for whatever reason, see the quick video below for a visual explanation of where to find the thermostat.

Will Running My Car Without A Thermostat Cause Overheating?

Before we talk about all effects that running a car without a thermostat will have, we first want to discuss the biggest myth that involves this matter. That’s the myth that running your car without a thermostat will cause it to overheat. This is not the case.

The reason why running your car without a thermostat won’t cause it to overheat is because it doesn’t regulate the temperature of the coolant. Instead, it only affects the flow of the coolant. Running the car without a thermostat means coolant will continuously flow through the engine in quantities larger than needed.

This means the engine is still cooled, but it will have a tough time maintaining its optimum operating temperature. However, coolant is still present, and the engine is still cooled. Therefore, overheating is not one of the effects and that includes everything from the engine to the car key.

A Closed Thermostat Does Cause Overheating

However, there’s one case in which the car can overheat because of the thermostat. That’s when you’re dealing with a bad thermostat stuck in a closed position. Coolant can’t flow to the engine if a thermostat is stuck in a closed position, which will result in the engine not losing its heat and overheating.

If you’re dealing with an overheating engine, check for a coolant leak around the thermostat housing or one of the cooling system’s hoses. The coolant stuck in the system will likely overheat, causing it to expand and find its way out through one of the hoses.

What Happens If You Run A Car Without A Thermostat

One thing that will happen without a thermostat is that your engine will have difficulty maintaining its optimum temperature. Remember, the thermostat is there to regulate the flow of coolant, which is done to ensure optimum engine temperature and allow it to achieve maximum efficiency.

This video will give you a good idea of what it means to drive a car with a bad thermostat.

It’s important to understand that not maintaining optimum operating temperature will result in the following things:

High Fuel Consumption

Higher than usual fuel consumption is one of the most significant side effects. Because the thermostat is gone, the engine will most likely run at lower than recommended temperatures.

This means fuel isn’t burned as efficiently, and a lot of fuel will be lost simply because it burns incompletely, which means the maximum energy potential isn’t being released. As a result, your gas mileage will shoot up, and there’s nothing you can do about this except for fixing the thermostat.

Engine Wear

Less than optimal temperatures also mean that lubricants of the engine (mainly engine oil) won’t reach their optimum temperature either. This means lubrication is less than ideal, so parts will start wearing down quicker. It’s not that the whole engine will blow up immediately, but less-than-ideal lubrication over extended periods will impact the lifespan of your engine and fuel system.

Check Engine Light

Logically, your car will warn you when driving without a thermostat. Common symptoms of this are a check engine light. If you use an OBD2 scanner, there’s also a code associated with this. It’s code P0128 which indicates that the car is telling you the coolant within the engine is taking longer to reach its optimum operating temperature.

Interior Heater Only Blows Cold Air

Another symptom of driving without a thermostat is that your car’s heater won’t function as expected. The heaters typically use hot coolant from the engine to warm the car’s interior if this is what the driver wants.

However, with the coolant constantly being cooled by the radiator and the fact that it doesn’t have enough time in the engine to warm up, there’s a lack of heat to warm up the interior. Even worse, the blower motor will still likely work which is the component that burns the most fuel (even if it is a small amount).

Is There A Difference Between Cold And Warmer Climates?

One thing we do want to emphasize is whether running a car without a thermostat is better or worse in different climates or if it makes no difference at all. The short answer is that it does make a difference; here’s why.

As we already established, having coolant run through the engine freely all the time will result in lower than recommended engine temperatures. There’s too much coolant in the system, and the engine can’t heat up enough.

However, this problem is less severe in warmer climates. That’s because the engine has an easier time heating up in warmer temperatures, diminishing the effects of the surplus of coolant in the system.

On the other hand, driving without a thermostat in colder climates will result in severe problems much more quickly. In colder climates, the engine is already too cold, and coolant is also running through its system (which shouldn’t be there).

Depending on how cold it is outside, this can result in significant engine wear and potential check engine lights. Do not drive your car without a thermostat in colder weather.

How Long Can You Run A Car Without A Thermostat?

This entirely depends on the climate you live in. In warmer temperatures, it’s theoretically possible to run your car without a thermostat for its entire life. In colder climates, your car may not survive a single trip because of the engine’s lack of properly warmed-up lubricant.

Is It Illegal To Run A Car Without A Thermostat?

Running a car without a thermostat is not illegal in any state. This is because a thermostat is not a safety risk and won’t affect other people on the road, or people inside the car, unlike driving without a differential, without a catalytic converter, or even without a cabin air filter. Instead, you’ll only do damage to your car over time.

What Causes Your Thermostat To Go Bad?

While the thermostat controls coolant flow, it must do so in good condition. If not, it will wear out faster. A bad thermostat could be caused by:

Overheating

The thermostat uses the heat it senses from the engine to open and close the valves. Then allow coolant to pass unto the radiator. If for any reason, the engine overheats, it affects the thermostat. This is because internal thermostat components are designed to function under normal operating temperatures. Hence, intense heat may damage its components.

Slush

As time goes on, most automobile coolant gets contaminated and wears out. When the coolant becomes contaminated, it changes into a thick slush-like substance. This slush may enter the thermostat, restricting the coolant’s flow or even stopping it.

The slush also causes the thermostat not to take proper readings. It also causes delays in opening and closing valves. This, in turn, causes the engine to cool too much, causing the thermostat to fail.

Duration Of Use

The thermostat continuously works with hot and cold coolants. After doing much of this work, it gets worn out. This will occur slowly that you won’t even notice it’s getting worse. Until one day, it shuts down completely. This is not new; most vehicle parts work that way. That’s why you need to replace them after some time. In the case of a thermostat, expect the part to last around ten years.

Improper Installation

When a thermostat is installed wrongly, it can quickly go bad—for example, installing a jiggle valve upside down. When this happens, no air will enter the cooling system. Another case is the thermostat being installed backward. In this case, the part that is supposed to face the engine will face the radiator.

This will make the part supposed to sense heat face the radiator instead of the engine. With this wrong installation in place, the valve will not open on time.

How Much Does It Cost To Replace A Thermostat?

Typically, it costs between $140-$300 to have a professional replace it. This includes installation and purchase costs. However, this amount may vary from car to car.

If you’ve got more questions then consider checking our articles on whether you can drive a car without a title, or if it’s legal to drive a car without a bumper, and many more!