Engine Overheating: Top 9 Causes and How to Avoid it?

Engine overheating is not just a minor inconvenience. It is the root cause of almost all car problems. If not addressed promptly, it can lead to severe damage and costly car repairs.

In this blog post, we’ll explore the top 9 reasons why engines overheat. We’ll also provide actionable tips to help you prevent this issue before it becomes a major problem.

So, without any further ado, let’s get started!

What is Engine Overheating? What are its Symptoms?

Simply put, engine overheating occurs when your engine generates more heat than it can effectively dissipate. All the internal combustion engines generate power by burning fuel.

However, not all the heat generated by burning fuel turns your wheels. The engine components also absorb a part of this heat that must be removed. Different mechanisms are in place for effective heat removal. The most common one is water cooling.

We’ll discuss the specifics of heat removal later, but here’s what you need to know. If any component of the cooling mechanism isn’t working properly, the engine overheats.

And overheating is unlike other minor issues with your car. It can cause serious damage to crucial engine components, leading to problems like warped cylinder heads and blown head gaskets.

Now, the big question is, why is your car’s engine overheating? That’s what we’re going to discuss mainly today. But before that, you have to know for sure that your engine is overheating. The first sign is usually the temperature gauge soaring into the red zone. That’s usually enough.

Still, here are a few other symptoms you should keep an eye on:

• Steam billowing from under the bonnet.
• Unusual noises coming from the engine, like knocking or rattling.
• A sweet smell coming from the engine bay (usually indicative of coolant leaks)
• Loss of power and high fuel consumption.
• The engine suddenly cutting out.

All these things are potential signs of engine overheating.

Top 9 Causes of Engine Overheating (+How to Fix)

Once you have established that your engine is overheating, you can look for answers to why is my engine overheating. So, here are the top 9 reasons that can cause your car’s engine to overheat. As each issue is unique, so we have added a quick fix for each one as well.

1. Faulty Water Pump

The most obvious reason behind the engine’s overheating is a failed water pump. The water pump operates by drawing cold coolant from the radiator. It then pumps this coolant into the engine block, absorbing heat from critical components.

After that, the coolant returns to the radiator to dissipate heat and cool. This cycle maintains a consistent operating temperature in the engine. So, when the water pump fails, coolant flow is disrupted. Since the engine can no longer dissipate heat effectively, it overheats.

How to Fix it?

To address a failing water pump, you should first diagnose the issue. Look for signs such as coolant leaks or unusual noises from the engine coolant. However, if you confirm that the pump is faulty, there’s no other solution than to replace it.

You will need to drain the coolant and remove the attached components. After removing the old pump, install the new one and ensure all seals and gaskets are replaced to prevent leaks. Finally, refill the cooling system with fresh coolant and bleed any air from the system.

2. Thermostat Stuck Closed

After that, the thermostat valve plays the most important role in regulating coolant flow in your vehicle. When the engine is cold, the thermostat remains closed, preventing coolant from circulating to the radiator. This allows the engine to warm up quickly, reaching its optimal operating temperature efficiently. Once the engine warms up, the thermostat opens, allowing coolant to flow, thus maintaining a temperature for optimal performance.

However, things can go severely wrong when the thermostat gets stuck closed as the coolant cannot flow to the radiator. It causes the engine temperature to rise uncontrollably. This situation often arises due to mechanical failure or corrosion within the thermostat that prevents it from opening.

How to Fix it?

To resolve this issue, check the coolant flow when the engine warms up. If there’s no circulation, the thermostat is likely stuck. Replacing it is usually the solution and can prevent further damage.

However, ensure that you use a thermostat that matches your vehicle’s specifications for proper functioning. After installation, refill the coolant and check for leaks before running your engine.

3. Coolant Leaks or Low Coolant Levels

Coolant is the soul of your car’s cooling system. However, if there’s not enough coolant in your car’s system, it can lead to overheating issues. Now, this can happen due to two simple reasons. One is that you haven’t checked the coolant levels in your car for a long period.

The second reason is leaks, which can be a bit of a headache. Coolant leaks can occur from various sources, including hoses and the radiator. If levels are severely low, you might notice puddles under your vehicle or a warning light on your dashboard.

How to Fix it?

If you’re simply dealing with low coolant levels, the solution is quite simple. All you need to do is top up the coolant, and you’re good to go. However, dealing with leaks is tough.

You have to inspect all the hoses and connections for signs of wear, damage, or leakage. If you find a leak in the radiator or water pump, these parts may need replacement.

4. Clogged Radiator and Hoses 

If coolant is the soul, then the radiator is the heart of your car’s cooling system. Similarly, the hoses connecting the radiator with the engine block also play a crucial role. Radiator hoses come in two main types: the upper hose and the lower hose.

The upper hose carries hot coolant from the engine to the radiator, while the lower returns cooled coolant. If the hose or the radiator gets clogged, it can lead to significant engine overheating. Radiator and hose clogs are quite common. Dirt, debris, or corrosion can build up over time, leading to blockages that cause overheating.

How to Fix it?

To remove the clogs, you have to flush the radiator using a radiator flush solution designed for this purpose. This process helps clean out any debris that may be obstructing flow.

Check hoses for blockages and replace any that appear damaged or corroded. Additionally, inspect the radiator fins for dirt or damage that could impede airflow.

5. Cooling Fan Not Working

The primary function of a radiator cooling fan is to enhance airflow through the radiator. This helps dissipate heat from the engine coolant.

While driving at higher speeds, natural airflow through the grille is usually sufficient for cooling. However, at low speeds or when idling, this airflow diminishes significantly. It makes the fan essential for maintaining optimal engine temperature.

Radiator fans can be categorised into two types: mechanical and electric. Mechanical fans are typically belt-driven and engage when the engine reaches a certain temperature. They operate through a fan clutch that allows them to spin faster or slower based on engine heat.

Electric fans, on the other hand, are controlled by temperature sensors and can turn on or off automatically as needed. This capability allows them to provide cooling only when necessary.

When a cooling fan fails to operate correctly, it can lead to engine overheating. Without adequate airflow through the radiator, the coolant cannot effectively dissipate heat. This situation is particularly problematic during stop-and-go traffic or when idling for extended periods.

How to Fix it?

First, test the cooling fan’s operation by observing whether it activates when needed. If it does not work, you may need to test the fan motor or relay responsible for its operation.

If repairs are needed, you may need to replace faulty components such as the fan motor, temperature sensors, or even the entire fan assembly in some cases.

For mechanical fans, ensure that the fan clutch is functioning properly. Additionally, check all electrical connections to ensure they are secure and undamaged.

6. Electronic Defects

The entire cooling system works in a coordinated manner. However, like other systems in modern vehicles, it also relies on electronic components and sensors. The primary sensor used by the cooling system is the coolant temperature sensor (CTS).

The CTS continuously monitors the engine coolant temperature and provides feedback to the ECU. If the temperature exceeds a predetermined threshold, the ECU activates the cooling measures. It includes turning on the cooling fan or adjusting the coolant flow through a thermostat.

If the CTS fails to provide accurate readings, the ECU may not trigger necessary cooling actions. This may lead to engine overheating.

For instance, if a CTS incorrectly reports a low coolant temperature, the ECU might delay fan activation. Conversely, if it falsely indicates high temperatures, it may shut down cooling systems prematurely. These miscommunications can result in excessive engine temperatures.

How to Fix it?

To address electronic issues, run diagnostic tests using an OBD-II scanner to check for error codes related to your cooling system. Identify any faulty sensors or modules that require replacement and take action accordingly. Also, inspect wiring connections for security and corrosion.

7. Low or Dirty Engine Oil

Engine oil lubricates moving parts within your vehicle’s engine, but that’s not the only thing it does. Another critical role of engine oil is to help cool down the engine. As the engine operates, it generates heat from combustion and friction between moving parts.

Engine oil helps dissipate this heat by circulating through the engine and carrying heat away from critical components. This cooling effect supports the vehicle’s overall temperature management system. It prevents overheating and ensures optimal performance.

When oil becomes contaminated with dirt, sludge, or metal particles, its ability to lubricate effectively diminishes. This increased friction can cause excessive heat build-up within the engine.

Additionally, low oil levels reduce the volume of lubricant available to circulate and cool engine components. Without adequate lubrication and cooling, parts of the engine can overheat.

How to Fix it?

To avoid engine oil-related problems, regularly check oil levels. If levels are low, top them up with quality oil as recommended by your manufacturer’s specifications. Similarly, changing the oil regularly is also essential. Follow manufacturer recommendations for intervals between changes.

Using high-quality oil filters during changes also ensures that contaminants do not circulate through your engine’s lubrication system.

8. Air Pockets in the Cooling System

Air pockets in a car’s cooling system are trapped bubbles of air that disrupt the flow of coolant. These pockets can form for various reasons, such as leaks, improper coolant changes, or radiator flushes. When air enters the system, it creates blockages that prevent coolant from circulating effectively. This leads to uneven cooling and can cause localised overheating in the engine.

How to Fix it?

To eliminate air pockets in your cooling system, you need to bleed the system effectively. Then, fill the radiator with coolant until it reaches the appropriate level. Next, start the engine and let it run for several minutes. This allows the coolant to circulate and helps push any trapped air out.

While the engine is running, you should observe the coolant level. If it drops, add more coolant as necessary. You can also gently squeeze the upper radiator hose to help dislodge any trapped air.

After a few minutes, turn on your car’s heater to its maximum setting. This will help circulate coolant through the heater core and remove air pockets.

Once you believe all air has been expelled, turn off the engine and allow it to cool down completely. Check the coolant level again and top off if needed. Repeat this process if necessary until no more air bubbles appear in the system!

9. Excessive Engine Load

This last one is not a cause per se, but yes, it can also cause your car’s engine to overheat. Some people have to drive with excessive loads. This puts extra strain on your vehicle’s engine and cooling system. This causes engines to overheat more quickly than normal conditions would allow!

How to Fix it?

There is no fix if excessive load is causing your car’s engine to overheat. All you can do is manage the excessive load effectively while driving. Reduce unnecessary weight inside vehicles whenever possible! Remove items not needed during trips. This will lighten overall loads significantly!

Also, heavy towing beyond the capacity limits specified by manufacturers should be avoided. Always check these limits beforehand so you don’t exceed them unknowingly!

Our Top Tips to Prevent Engine Overheating

There are two main causes of engine overheating. One is neglecting maintenance, and the other is a component reaching its lifespan. The maintenance part is quite important as it can help extend the lifespan of critical components like the water pump.

Still, here are some expert tips that will help you keep running on the road smoothly:

• Coolant is the soul of your car’s cooling system. Make it a habit to check coolant levels in your car every week or at least twice a month.
• The quality of coolant is as important as its quantity. Use only manufacturer-recommended coolant mixes, and don’t try to save money by choosing cheaper brands.
• Don’t take engine warning signs for granted. Overheating can trigger not only the temperature warning but also the engine management light. So, watch out for these signs.
• Ensure you are using the correct type of oil for your vehicle and check oil levels frequently. Low or incorrect engine oil can increase friction and heat within the engine.
• Minimise idling time, particularly in hot weather, as it restricts airflow to the engine and can lead to engine overheating.
• Avoid aggressive driving habits such as rapid acceleration or high-speed driving. It can put extra stress on the engine and lead to overheating.
• Have your cooling system flushed and cleaned every 40,000 miles. It will help remove any build-up that could impede performance.
• Schedule regular check-ups with a mechanic to inspect your cooling system, including the radiator, thermostat, and hoses. It’s recommended that this service be done every year.

Frequently Asked Questions

1. Is it safe to drive if my car’s engine is overheating?

It depends. If the temperature gauge is just approaching the red region, it’s generally safe to drive a few hundred miles. Let your car cool down and see if the issue persists. Slight engine overheating is quite common during harsh summers, especially if you’re driving an older car.

However, if you see the temperature gauge climbing quickly, you should stop immediately. Extreme overheating can cause severe damage to your engine. You risk warping the cylinder head or damaging the head gasket. In the worst-case scenario, overheating can also seize the engine.

2. Why is my engine overheating, but the coolant is full?

Your engine can overheat even if the coolant is full. As explained in detail above, there are multiple causes of engine overheating. For instance, an airlock in the radiator can reduce coolant circulation, even if the reservoir appears full.

A stuck-closed thermostat will also prevent the coolant from flowing properly through the engine. Additionally, a malfunctioning water pump or a clogged radiator can restrict coolant flow and cooling efficiency.

3. Is it safe to check the engine compartment while it is overheated?

No, it is unsafe to check the engine compartment while it is overheated. The engine and components can reach extremely high temperatures, posing serious burn risks. Opening the hood too soon may release hot steam or boiling coolant, which can cause severe injuries.

You must wait until the engine has cooled down completely before inspecting it. This usually takes at least 30 minutes after turning off the vehicle. When you do check under the hood, wear protective gloves and safety glasses for added safety.

4. What should I do if my car is overheating?

If your car is overheating, you have to take immediate action to prevent further damage. However, the exact course of action will depend on the severity of the issue. So, when you first notice the signs of engine overheating, pull over safely and turn off the engine.

Allow the engine to cool down for at least 30 minutes before opening the hood. Once cool, check the coolant reservoir level and look for leaks or damage in hoses and connections. If the coolant is low, add the appropriate type of coolant or water as a temporary fix.

Then, continue to drive, keeping an eye on the temperature gauge and listening for unusual noises. If the temperature is still rising, stop and call for roadside assistance or a road truck. Avoid driving until you identify and fix the problem to prevent further damage.

5. How to check the engine coolant levels?

Here’s how you can check the engine coolant levels correctly:

• First, ensure your vehicle is parked on level ground with the engine turned off.
• If your car’s engine was running, wait until it cools down.
• Open the hood carefully and locate the coolant reservoir.
• Look for markings on the side indicating “low” and “full” levels.
• If the coolant level is below “low,” add a mixture as specified in your owner’s manual.
• Use a funnel for accuracy and avoid spills on hot components.
• After adding coolant, replace any caps securely before closing the hood.
• Drive for a few miles and repeat this process once again.

Wrapping Up: Causes, Symptoms, and Prevention Tips for Engine Overheating

In conclusion, engine overheating is not something that you can take for granted. Even if there is so much as a hint that your car’s engine is overheating, you must take action.

And prevention is even better than cure. It can save you time, money, and frustration. So, schedule regular maintenance checks and monitor your engine temperature gauge regularly.

Use our tips to keep your car running cool and smoothly for years to come. Please read our blogs to learn more about car maintenance and keep your vehicle in top condition.