10 COMMON REASONS FOR OVERHEATING CAR PROBLEMS -

Overheating car problems are one of the most common problems a driver and car owner can encounter.

The cooling system of the car is under constant pressure and high temperature which, over time causes material and parts fatigue.

This is why this problem is more often in used cars.

Hopefully, this article will help you solve the engine overheating car problem or at least find out the reason why it’s happening.

Besides the article, you can watch a YouTube video at the end of the article or on our YouTube channel.

WHY IS THE ENGINE COOLANT SYSTEM SO IMPORTANT?

This question is perhaps a nuisance but I guess a few words of introduction won’t hurt.

Anyway, the inner combustion engine produces a lot of heat while running. If that wasn’t controlled by the coolant system, the engine would overheat and get damaged.

So, proper engine cooling is at the same level of importance as proper engine lubrication (engine oil).

If you’re interested in exactly how the coolant system works, click here for a great explanation on Wikipedia.

OVERHEATING CAR SYMPTOMS

The temperature gauge needle starts rapidly moving over the middle: the first and most obvious sign. Always pay attention to the gauge while driving as this enables you to act on time and perhaps prevent engine damage.

Lack of power: once the overheating starts, you’ll notice pretty soon that the car is losing power. It is simultaneous with the engine temperature going up.
Warning light on the dashboard: in most cars when this light goes on, the car is very close or is already overheating.
Steam comes out of the engine bay: yes, just like in the movies. This is the final phase in an overheating car. This happens if you continue driving despite the overheating problem. When this happens, the engine has already had a major overheat. In this case, just pull to the side of the road, pop the hood and stay away from the engine bay until it cools down.

For some useful tips on what to do if the engine overheating problem happens, click here to read the article.

OVERHEATING CAR DAMAGE-WHAT CAN HAPPEN?

If you take action on time, probably nothing. The car engine has a short period of tolerance to this problem and if you react properly, the damage will be minor or none.

On the other hand, if you drive an overheating car for a prolonged period of time you will cause major damage to the engine.

All parts of the cooling system are more or less expensive or complicated to replace (depending on the car model, vintage, accessibility, etc). The point is that a more or less expensive and replaceable car part can cause major damage to the engine.

By major damage, I mean a blown head gasket which means opening up the engine (taking off the cylinder head, repairing or replacing the cylinder head, etc.) In any case a very costly and timely repair.

To put it simply, a cheap part like a leaking hose can cause a partial or complete engine overhaul.

If you’re in a situation where an engine overhaul (rebuild) is imminent, click here for some advice on that topic.

Whatever the case may be, all of this can be prevented if you pull your car to the side of the road once the overheating problem starts. In some cases, you may be even able to do the repair yourself (like a broken hose or loose clamp).

With an overheating car, attention and prevention will save both your car engine and money.

10 COMMON REASONS FOR OVERHEATING CAR PROBLEMS

The reasons are sorted from the most common to the more rare problems.

1. TOO LOW OR TOO HIGH LEVEL OF ENGINE COOLANT

This is the most common reason for overheating.

Various reasons can be a loose cap on the coolant reservoir, small, barely or non-visible leaks, low-quality coolant that evaporates over time, and others.

The opposite is too much coolant which produces additional pressure in the system.

Additional pressure also leads to car overheating.

The system pressure is normal when the coolant level is between minimum and maximum (the middle mark).

Make regular check-ups of the coolant system and everything should be OK. If needed, add some, but to the middle mark on the coolant reservoir (bottle).

Adding coolant frequently means that you have a problem; for instance a leak somewhere in the system.

Take care of it as soon as possible as it can lead to bigger problems and expenses.

2. COOLANT HOSE LEAKS

Another very common mishap that causes engine overheating.

Over time, due to variations in temperature and a harsh environment, the hoses get brittle and lose their elasticity (ruptures and small cracks start to appear).

This eventually means leaks and losing coolant which will cause car overheating.

Coolant hose leaks are best solved by prevention.

The best way is to make an inspection from time to time (perhaps once a year) to see that all of the coolant hoses are still flexible and elastic.

This is done by hand; just give the hose a press or a slight bend and see if the surface of the hose shows any cracks. Small, minor cracks mean the hose is at its end and you should replace it as soon as possible.

Replacement is pretty simple and, again depends on the accessibility of the hose. Mostly a do-it-yourself-job.

3. LOOSE HOSE CLAMPS

A very common cause of engine overheating.

Over time and due to pressure, the clamps tend to loosen up or even break.

Furthermore, the hose that the clamp holds in place gets shrunk over time, causing the clamp to lose grip.

A loose hose means leaking and this means an overheating car.

Solving this problem is very simple, just buy the same coolant hose and the same diameter clamp and replace it.

If it’s accessible (which is not the case with many modern cars), you can do it on your own.

More about how to solve various coolant leak problems in a separate article which you can read by clicking here.

4. BROKEN THERMOSTAT

The thermostat is essentially a switch. Better said a valve that automatically reacts to the coolant temperature.

It’s located in the coolant system so it can prevent or allow the flow of coolant. When the engine is cold, the thermostat is in the closed position (coolant flow is closed). This means that the engine heats up more rapidly.

Once the engine starts reaching its working temperature, the thermostat starts opening thus letting the coolant flow freely through the entire system.

If the thermostat is faulty, it gets stuck (unable to release or stop the coolant flow).

If it gets stuck in the open position, the car cannot reach the working temperature and the engine stays cold.

However, if it gets stuck in the closed position, then you get an engine overheating problem due to the lack of proper coolant flow.

Be prepared for at least one encounter with this problem, especially if you own a high mileage car.

Not that much of a fuss to replace, not even that costly. Mostly depends on the accessibility of the thermostat housing.

5. THERMAL SWITCH (COOLANT FAN SWITCH) ON THE RADIATOR

The thermal switch is an electrical switch that reacts to the temperature of the coolant.

This switch activates the radiator fan once the coolant exceeds the working temperature.

It works on the same principle as a thermal switch on a clothing iron, for instance.

When the airflow through the radiator is weak (for instance in city driving), the fan has the main role in lowering the coolant temperature.

Over time, due to material fatigue, the thermal switch tends to malfunction thus not activating the fan. This leads to the rise of coolant temperature and eventually engine overheating.

The solution to these problems is a thermal switch replacement, any improvisations are not possible.

The switch is usually located on the car radiator, it’s easily recognized as a big screw with wires or a wire connector coming from it.

Replacing it is a simple job (screw out-screw in), the only problem can be the accessibility to the switch itself. Thanks to most engine bay designs, it can be a pain to replace. Not impossible, but still a pain.

6. BROKEN WATER PUMP

The car water pump keeps the coolant flowing through the engine.

The pump is belt-driven so once you start the car the water pump immediately starts to push the coolant through the engine.

It is essentially an engine-driven turbine.

The most common faults that can cause a water pump failure are the impeller fins being damaged/broken or the water pump bearings wearing down.

Replacing the entire water pump is the solution in this case.

This used to be fairly simple with older car models. The car water pump was mounted on the outer side of the engine and driven by a separate ribbed V-belt. If the water pump broke, you could change it without a big intervention.

But with today’s engine layout this is mostly not possible.

In today’s cars and even most used cars, the water pump is driven by the camshaft timing belt.

This means that the water pump is a part of the timing belt system and if it fails, it can cause major engine damage.

This is, in my opinion, the bad side of that engine construction.

The good side is that the water pump is changed every time you change the camshaft timing belt.

If it’s done properly, with quality parts, and with a guarantee, you should never encounter a water pump problem.

So, just make the timing belt replacement on time, with quality parts, find a good mechanic, and you’ll probably avoid this problem.

If you want to know what are the most common signs of a bad water pump, click here for a separate article on that topic.

7. CLOGGED OR CRACKED CAR RADIATOR

A car radiator’s main purpose is to lower the temperature of the engine coolant.

The coolant carries away the engine heat and once it’s inside the car radiator it’s cooled down by the airflow.

Coolant flows nonstop during driving through the radiator.

Over time, due to all kinds of dirt and filth, the fins and small pipes on the radiator get clogged up.

This leads to less airflow through the radiator and this again means less cooling down.

If cracked, you’ll recognize it by the leaks that start to appear around the radiator and frequent coolant loss in the system

In this situation, engine overheating is inevitable.

The two most common ways of solving this are radiator cleaning or complete replacement.

Cleaning can be done (in case of a clog) by flushing the inside of the radiator (there are various products that you can buy).

The outside cleaning is usually solved by a good pressure wash.

In case of a crack, I could only recommend a complete replacement.

Any mending or improvisation is possible but is mostly short-lived.

Whether replacing or cleaning, it’s a pretty complicated job mostly due to accessibility issues. In most modern cars it involves much disassembly.

You can read more on how to fix a car radiator leak by clicking here.

8. CLOG IN THE COOLANT SYSTEM

The coolant system is highly dependent on a good and proper flow through the whole system.

Coolant goes through various hoses, the radiator, canals in the engine block, etc. that can get clogged over time.

To tell you the truth, this is a problem that is rarer as it takes a lot of time for the clog to build up.

The most common causes of these clogs are using tap water instead of coolant (which causes scale build-up), using some sort of leaking “remedies” (especially when the radiator is leaking), or hoses of small diameter that are more prone to clogging up.

Using low-quality coolants can also cause problems (high-quality coolants contain substances that help prevent clogs).

In any case, better safe than sorry when it comes to clogs.

Use quality coolant (recommended by the manufacturer), change old coolant hoses on time (both for cracks or clogs), and avoid using tap water in the system (only in emergencies).

If the clog is somewhere in the engine canals, replace the old coolant and flush the engine out completely.

9. CRACKED OR DAMAGED HEATER CORE

This is also a problem that rarely occurs.

Mostly happens to older cars.

You see, besides the engine radiator that cools down the engine coolant, there is another smaller one.

It’s basically the same as the engine radiator (similar construction) and its main task is to heat the passenger cabin.

Hot coolant goes through the heater core and the cabin ventilator blows air through it, thus causing the cabin to heat up.

Breakdowns are rarer with heater cores, mostly because of the fact that they are inside the passenger cabin and more protected.

However, over time, due to material fatigue, it can start to leak or clog up.

You’ll notice this problem since coolant leaks into the passenger cabin before engine overheating starts.

Replacement is not that much of a problem (same principle as the engine radiator).

The bigger problem is reaching it in the cabin. Lots of trim dismantling, bad working positions, and lots of tight spots are just some of the reasons why this breakdown is so complicated.

In this case, I would only recommend a replacement with a new heater. I don’t even recommend repairing the old one (only if it’s a rare car model and the cabin heater is hard to find).

Just imagine tearing apart half of the car cabin and then putting it all together only to see leaks after a few days.

You can read in more detail about the bad heater core problem by clicking here.

10. BLOWN OR DAMAGED HEAD GASKET

Between the cylinder head and the engine block is the main seal that assures a perfect connection.

Without it, the engine would not function properly. The moment the car is started, oil and coolant would leak everywhere and the engine would lose compression in the cylinders.

When the head gasket is damaged, besides leaking, oil and coolant get mixed up together. The reason is that the gasket separates these liquids and their canals in the engine block from one another.

Tell-tale signs of this problem are constant overheating (less, in the beginning, progresses as the gasket sealing gets worse)

But most evident is that when you open the coolant reservoir, you’ll see a foam-like substance inside. This is the result of the coolant and engine oil mixing together.

Once you see this, you’ll surely know that the head gasket is totally blown and you need a replacement ASAP.

It is possible to continue driving (depending on the previous level of overheating) but the situation will get worse over time.

You have to know that this is a very costly repair as it means opening the engine. Any delay on this repair will only get you into more expenses.

If you drive a used old car, make sure that you ask for the repair price. A lot of times the repair is simply not worth it.