Why Is My Car Overheating?

Symptoms and Fixes for an Overheating Car Engine

Why Is My Car Overheating? - Expert Advice to Diagnose & Fix

If your vehicle has been getting too hot, or is steaming, smoking, or giving off a sweet smell, your car is overheating. These are never good signs. An engine that’s overheating needs immediate attention. Allowing it to run can lead to serious and irreversible damage. An overheating engine that’s ignored will cost thousands to fix or replace.

In this video and the post below, we’ll highlight the most common signs and symptoms of car overheating. We’ll take a look at how you can diagnose different parts of your car that could be behind an overheating car. This will help determine if you have an issue with the engine itself or a different part of your vehicle. 

What Are the Symptoms of an Overheating Car Engine?

Symptom of Engine Overheating is a high temperature Gauge Reading

Here are some symptoms you should look out for when your car engine is overheating. 

1. A high temperature-gauge-reading that’s within the “red zone.”

2. Car smoking under the hood, grille, or underneath the vehicle. 

3. A sweet smell in the air caused by boiling coolant.

4. Coolant leaking from under the car. 

What to Do When Your Car Is Overheating

If you’re driving and you notice smoke or steam coming out of the hood, here’s what you should do. 

Step 1. Get off the road and park your car somewhere safe. Turn your vehicle off. You don’t want to leave it running while your car is overheating. Leaving it running with your car overheating will cause severe engine damage.

Set car to high heat with the engine off to cool off overheating car engine

Step 2. Put the key back in the ON position and turn on your blower motor. Set the heater to its highest setting to help draw heat away from the engine compartment.

Step 3. Check to see if you have any steam or smoke still coming out. If everything is clear, open the hood slowly. Watch out for hot air that may come up in your face. If you have any protective gear for your hands and eyes, put it on. 

Step 4. Let the hood stay open until all the heat dissipates from the engine compartment. 

Step 5. Once all the heat is out, it’s time to find out why your car is overheating. Below are some parts of your car that could be causing the engine to overheat. You can also watch this video to learn how to diagnose the problem.

Causes of a Car Overheating

1. Leaking Coolant

A cause of car overheating is Leaking Coolant

The most common cause of the engine that’s overheating is coolant leaking. In some cars, you’ll find a cooling system that comprises a pressurized sealed unit while in others, you’ll find a radiator with a separate overflow tank

Whatever the case may be, you’ll want to check the quantity of your coolant. If it’s below the recommended level, it may be the cause of your engine overheating. Coolant doesn’t just disappear. You’ll need to find out why it’s low. 

There could either be an external leak in the water pump or radiator, or an internal leak that sends the coolant to the engine cylinders. When the coolant gets into any of the engine cylinders, it gets burned up in the combustion process. This normally causes white smoke to come out of the tailpipe. 

Also, you may have coolant that is too old. The water that’s mixed with the concentrate may have evaporated over time leading to a drop in its level. At this point, you’ll need to flush it out of the system and replace it with some new coolant. 

2. Coolant Discoloration 

Whether your coolant is low or not, it’s always best to open the cooling system and check its quality. This should be done when the car has completely cooled off. Never open the coolant reservoir when the system is hot. 

Your car’s coolant performs several functions. It helps to cool the engine when the temperature is high and helps to maintain the right conditions when external temperatures are low. 

If you don’t have enough concentrate mixed with water, the latter could freeze when external temperatures fall below 32° Fahrenheit. If you have too much concentrate mixed with water, the system will not be able to dissipate heat effectively. This causes the engine to operate outside its optimum operating temperature, leading to overheating. 

Comparison of New Engine Coolant and Old Coolant From Car Overheating

Difference in old from car overheating and new coolant

To check the condition of the coolant, take a sample from the reservoir and compare it new coolant that has been mixed correctly. On this particular vehicle, there was a big difference between the old coolant and the new coolant. 

However, you can’t always go by looks. It’s important to test the fluids that run through your vehicle’s system. A coolant and battery refractometer is one of the best tools to use. You can get one at 1AAuto.com. All you have to do is put a drop of coolant on the refractometer. It will generate a chart that shows you the freezing point of the coolant. 

A perfectly mixed coolant that contains a 50-50 mix should have a freezing point of about -32° Fahrenheit. This is often more than enough in most areas. However, those that live in an extremely cold environment may want to use a different mix of about 60% coolant and 40% water. If your coolant test shows results that are off the recommended freezing point, you’ll need to flush the coolant out of the system and replace it. 

50/50 Prediluted Coolant
Concentrated Coolant

You can either opt for 50/50 pre-diluted coolant or concentrated coolant. If you go for the latter, follow the chart provided to learn how to dilute it yourself. Remember to always pick the type of coolant that’s appropriate for your vehicle.

3. Dirty or Clogged Radiator Fins Can Cause Car Overheating

Damaged radiator fins

When the coolant absorbs the heat generated by the engine, it’s sent to the radiator via tubes. Air is then let in from the outside and passed through the cooling fins to lower the temperature of the coolant. Which, then lowers the engine temperature.

If the fins are damaged, pinned over, dirty, or clogged, they may not be able to release the heat into the ambient air. This may then cause the engine to overheat. Most cars provide enough access to the radiator fins. If they are blocked by leaves, dirt, or bugs, they can be cleaned. 

4. Malfunctioning Cooling Fan

Cooling Fan

The cooling fan is located on the engine compartment side of the radiator. It helps to pull in air through the cooling fins to keep the engine cooled. Some vehicles have an electric cooling fan like the one shown above. It’s operated by an electric motor powered by the car’s computer. Others have a thermal fan clutch attached to the engine water pump. In both cases, if the fan does not work like it’s supposed to, you’ll have no air coming in. This can cause the engine to overheat. 

5. Failing Water Pump

Water Pump

Where the cooling system has a thermal fan clutch, the clutch is normally connected to the water pump via a pulley. The pulley is driven by the serpentine belt. 

As it rotates, it causes the impeller that’s found inside the water pump to draw coolant from one side and let it out through the other side. This helps to maintain a constant flow of coolant within the system. 

If your serpentine belt is too weak, worn out, or has fallen out; it may fail to rotate the water pump pulley as required. In some cases, you may have a weak serpentine belt tensioner that’s not able to put enough pressure on the belt. The belt may, therefore, not be able to turn the pulley fast enough for coolant to flow as needed. This may leave you with an engine that’s overheating. 

6. Malfunctioning Thermostat


Your engine thermostat may be located inside a housing that’s attached to the cooling system through a hose. When you take it out of the housing, you’ll notice that it has a spring. The spring contracts whenever temperatures rise within the cooling system. 

This allows the valve at the end of the thermostat to open, allowing the coolant to flow. This goes on until the engine gets to its normal operating temperature. If your thermostat is malfunctioning, it may prevent the coolant from flowing. This then causes the engine to overheat. 

7. Damaged Coolant Temperature Sensor

Coolant temperature sensor

The coolant temperature sensor (CTS) measures the temperature of the coolant and sends this information to your car’s computer. It tells the car’s system how much heat your engine is giving off. With this information, the computer can turn on the cooling fan and calculate the fuel-to-air mixture required within the engine. 

If the CTS is not functioning properly, it could cause your engine to overheat. You may also experience issues with how the vehicle is running. You can have your coolant temperature sensor checked to confirm whether it’s damaged. The wiring that connects to it could be chewed, broken, or frayed. 

8. Blocked Cooling System

A blocked cooling system will always lead to your engine overheating. To find out whether you have a blockage in your system, start by looking at the coolant. If you notice any foreign particles, your system could be blocked by dirt or debris. 

Check your cooling system hoses to see if they are pinched or collapsed. You can start with the heater core hoses which lead to the firewall. Check for leaks especially where the hoses connect onto something or are rubbed against other parts of the car. 

9. Flapping Air Dams 

Flapping air dam

Air dams funnel air to where the radiator is located. They are found at the front lower portion of the vehicle. In some cars, they are built as part of the front bumper while in others, they come as a separate part that can be attached or removed. If they are not connected properly, they could flip over and block air from getting to the radiator. This then causes the engine to overheat due to a lack of adequate airflow. 

10. Broken or Missing Skid Plate

Broken or missing skid plate

A skid plate is a material that is fixed to the underside of a car. In addition to protecting the parts of the car closest to the ground, it helps to streamline airflow and keep the cooling fans working properly. 

If your skid plate is broken or you had it removed, it may interfere with the aerodynamics of your car. This can limit the amount of airflow directed to the engine compartment for cooling leaving you with an engine that’s overheating. 

More on fixing the splash shield

11. Towing Too Much

Towing something super heavy can cause your engine to overheat. This is especially if you’re tagging along something close to or beyond the upper range of the car’s towing capacity. It causes a lot of stress to your engine which then produces a lot of heat. 

It’s always best to know your car or truck’s limitations. You must stay within the recommended capacity. Always consider the weight of the additional luggage you may have strapped to the roof and trunk/bed as you tow stuff behind you. It also counts when it comes to determining how much your car can handle. 


A car that’s overheating shouldn’t mean the end of the world, especially if you take care of it as soon as possible. It’s always best to address the problem immediately when you notice the temperature gauge shooting too high. If you keep driving, you could cause detrimental damage to your engine. 

The areas highlighted in this post are a good place to start if you’re diagnosing an overheating car engine by yourself. As you check for mechanical failures and other defects, confirm from your owner’s manual that you’re within your service intervals. If you’re behind on maintenance, you’ll need to catch up. 

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Why is My Car Overheating? Causes and Symptoms - 1A Auto
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Why is My Car Overheating? Causes and Symptoms - 1A Auto
Have you ever had to ask "why is my car overheating?" If you have, you know how scary and concerning the symptoms can be. Read how our mechanic diagnoses and fixes an overheating car engine.
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1A Auto
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