Why Do Cars Overheat?

Why Do Cars Overheat?

Though rare with modern vehicles, even a well-maintained car can overheat. A car engine whose temperature runs too high can threaten your safety and cause damage. If your car’s temperature rises too fast or rises beyond safety limits, the best thing to do is kill the engine and have the vehicle towed to specialists. 

The most common reason cars overheat is a faulty cooling system. Other causes include low oil level, malfunctioning thermostat, worn-out accessory belts, and faulty radiators. 

There are many different causes for an overheating car engine. Knowing what the problem is can lead you to an appropriate solution that protects you and your car from damage and injury. The steps you take could mean the difference between replacing a $30 thermostat or paying thousands for major repairs. Here are the top causes for car overheating. 

Faulty Cooling System

Why Do Cars Overheat?

All car engines have a cooling system that makes use of some fluid to keep the temperature of the engine down. If the cooling system has a leak or blockage, the coolant might not circulate as it should. Circulation can also be affected by a malfunctioning pump. 

When the coolant doesn’t flow through the engine system, parts of the engine can become too hot. Improper circulation can overheat your engine even during freezing weather, not only in hot climates. 

Check your coolant level whenever your car’s engine shows signs of overheating. Ensure there’s enough coolant in the system. If the coolant level is low, that may indicate a leakage, blockage, or pump defect. Contaminants within the coolant may also lead to high temperatures. 

In most types of cars, you can easily check the coolant level yourself. Pop the hood of your car and carefully open the radiator cap. Ensure the radiator cap has cooled down before attempting to open. To be safe, wait at least half an hour after switching off the engine before you check the coolant level. 

Keep in mind that if the engine is hot, the coolant will be under high pressure. So when you open the radiator cap, the coolant will jet out in a very hot stream. This could easily burn you and others around you. 

Leaking Coolant

The most common cause of a faulty cooling system is when the car coolant leaks out. In normal situations, the coolant flows through the engine depending on how hot the engine is. The thermostat regulates the coolant flow, releasing more when it’s hot and less when the engine is cool. 

When there’s a leak, the flow is compromised. If you suspect a coolant leak, some of the most common leaking points could be:

  • Hoses
  • Radiator
  • Water pump
  • Freeze plugs
  • Head gasket
  • Thermostat housing
  • Cylinder head
  • Automatic transmission

Malfunctioning Thermostat

Your car’s thermostat controls how much coolant is released into the engine system. When the engine runs too hot, more coolant flows through. 

However, when the thermostat malfunctions, it may not be capable of dispensing the correct amount of coolant. Too little coolant in a running engine will most likely result in poor engine heat transfer and an overheating engine. 

Replacing a malfunctioning thermostat takes just a few minutes and doesn’t cost much. Check your thermostat each time you take your car in for service. If your thermostat has a problem, unless you’re sure of what you’re doing, let an expert take care of making the replacement. 

Worn Out Belts

If your car engine is running dangerously hot, some of the first things you should check are your fan belts, serpentine belts, and other accessory belts. If any of the belts is either loose or slipping, that could be the cause of the rising temperatures. 

Your car’s fan belt is powered by the car engine. The belt works by spinning some engine components, thus providing power to the cooling system, a/c system, electrical system, and steering system. 

If any of your engine’s belts wear out, become damaged, or get loose, the engine components won’t be able to spin at the correct speed. Slower speeds lead to decreased power for all or some of your systems, including the cooling system. 

By not replacing or tightening your belts in time, you may end up paying thousands for repairs and replacements. Apart from the cooling system, some other dangers include dimming headlights, radios not functioning, and batteries not charging. 

Most vehicle manufacturers recommend changing your belts after every 75,000 to 100,000 miles. Regular inspections can check for thickness, cracks, wear, and tear to determine whether you need a replacement. 

Radiator Problems

Why Do Cars Overheat?

For most engine types, the radiator keeps the engine at an ideal automotive temperature range of between 195 to 220 degrees Fahrenheit (90 to 105 degrees Celsius). If the engine gets any hotter, the heads and pistons may melt or soften, leading to malfunctions.  

A radiator works by conducting heat from the cool air outside the running car through the hot engine via the flowing coolant. If the air can’t cool a properly-flowing coolant, the engine will heat up excessively. Some of the most common causes of radiator trouble include:

  • Poor airflow through the radiator
  • A clogged or blocked radiator. Rust, sediments, and small insects can plug the circulation paths.
  • Accumulated contaminants in the radiator’s water jackets
  • A deficient radiator cap, releasing pressure
  • A collapsed radiator hose

Low Oil Levels

Engine oil keeps the moving parts lubricated and functioning properly. If your engine oil is low, there will be greater friction between moving parts. Additionally, there will be more stress on your cooling system which will have to work harder to keep your engine within a safe temperature range.   

In addition to lubricating moving parts, engine oil removes a significant amount of engine heat. If your engine level is low, your temperature control will be compromised. If your car overheats, check your oil dipstick. 

Most car manufacturers recommend checking your oil at least once every month. When you check your dipstick, you’re checking the oil level and for signs of oil contamination. To check your dipstick:

  1. Make sure the car engine has been off for at least ten minutes. 
  2. Pull out the dipstick.
  3. With a clean lint-free rug, wipe off the whole metal length of the dipstick.
  4. Insert the dipstick back into the pipe. 
  5. Pull out the dipstick again and check the thin film of oil against the markings on the dipstick. 
  6. If the oil reaches the point marked ‘Full’, rub a little between your index finger and thumb. If it leaves a dirty smudge then you need to change your oil. 
  7. If your oil is in the ‘Add’ range, you need to top up your oil. 

To top up, find the cap indicated as ‘Oil’ or ‘Oil Cap’. In some cars, the cap might be blank. Some cars may also include a description of the grade of oil to use. Unscrew the cap and add oil. You can recheck your dipstick after about an hour of running the engine. Ensure you check at least ten minutes after switching off the engine.

Gui Hadlich

Hey there! I'm Gui. To be honest, I'm not really that interested in cars. But what I'm really, really not interest in is spending lots of money fixing my car up. Thankfully, I have a father-in-law who's obsessed with cars and a brother getting a PhD in internal combustion engines, so I get to learn about fixing cars. And with Fixing Engines, I hope to help you save a lot of money and take good care of your cars.

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