Why Is My Engine Overheating? (15 Reasons Why)

Generally, engines run pretty hot to keep it running smoothly. However, an overheating engine can be dangerous, and you should never overlook it.

If your engine is overheating, you will probably want to know why. We did some digging, and here is what we discovered!

Why Is My Engine Overheating?


1. Low Engine Oil

All cars require engine oil to lubricate the moving parts within a car’s engine, which will also help control the temperature within a car.

However, not having enough oil or oil that is very old that has deteriorated can make your engine overheat.

Further, this occurs because the moving parts in your engine will not move smoothly, and the excess friction will make the engine hotter, eventually overheating.

Luckily, you can avoid this by regularly changing your engine’s oil, which should be done every six months or 3,000 miles, depending on your car.

2. Improper Coolant

If you recently got a new brand of coolant in your car and it started overheating, you may be using the wrong kind of coolant.

Usually, this will be the case if there is nothing seemingly wrong with your engine, such as a leak.

Fortunately, you can flush the whole cooling system and then add the ideal type of coolant for your engine.

3. Bad Radiator

Your car has a radiator that takes heat out of its hot coolant to let the coolant cycle into the engine, which will cool it again.

However, a bad radiator will not cool the hot coolant, meaning that the hot coolant will stay hot, making your engine overheat.

Usually, you would need a mechanic to check what is wrong with the radiator, which could be a bad radiator cap, leaks, or a broken fan.

4. Faulty Water Pump

A water pump moves coolant fluid to let the coolant flow in your car’s cooling system.

However, a faulty water pump will not efficiently pump the coolant, which means that your engine will remain hot.

A water pump can be faulty due to various reasons, including a leak, but it is recommended that you check the pump shaft and impeller vanes.

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5. A Clogged Hose

If you notice there is no coolant leaking from your engine, but the engine is overheating, your coolant hose may be clogged.

Normally, a clogged coolant hose will occur because dirt or sediment from the road enters the coolant hose.

If the coolant hose is clogged, your car’s coolant fluid will not properly flow through your engine, which will make your engine overheat.

That said, you can tell if your coolant hose is clogged if you have a cool upper hose or a cold lower radiator hose.

6. Failing Engine Coolant Temperature Sensor

If you have a more modern car, your car will have an onboard computer that controls the cooling fan’s operation.

Generally, the onboard computer will rely on data from the engine coolant temperature sensor to know when it should turn on the fan.

However, the onboard computer would be unable to properly operate the fan if the engine coolant temperature sensor fails, causing the engine to overheat.

7. Damaged Thermostat

Similar to a regular thermostat, an engine thermostat regulates the temperature in your car’s engine.

Normally, the thermostat will stay closed if the engine is cold, keeping the coolant from moving from your car’s engine to the radiator.

However, the thermostat will open when the engine gets warmed up to let the coolant fluid enter the radiator.

As such, the radiator works like a heat exchanger to transfer the coolant’s warmth to the outside air, keeping the engine’s temperature within a specific range.

Still, a faulty thermostat stuck in the closed position will not let any coolant flow to the radiator when the engine is warm, leading to an overheating engine.

8. External Heat

External Heat

While your engine naturally runs fairly hot when you drive, the external temperature can worsen your car’s likelihood of having an overheating engine.

Normally, extreme weather would make your car’s engine overheat if you already have an issue that could make your engine overheat.

For instance, a small coolant leak may take some time for your engine to overheat, but hotter external temperatures can make your engine overheat faster.

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As such, an engine with no problems will not likely overheat from the hotter summer months unless there is an underlying issue.

9. Lack Of Coolant

If you have not changed your car’s coolant in a long time, your engine is properly overheating because there is not enough coolant in it.

Generally, your engine overheats because there will be no coolant circling throughout the engine, making the engine get hotter.

When your engine’s coolant level is below the ideal level, you can usually top it off with new antifreeze or coolant until it reaches the desired level.

However, you will need to mix water and coolant or antifreeze in an equal amount if you add new coolant to an empty reservoir.

10. Coolant Leaking Internally

If you suspect a coolant leak but do not see it outside your car, you may have a coolant leak inside your engine.

Normally, coolant will leak from within the engine because of a cracked engine block, cracked cylinder head, or damaged head gasket.

When the coolant leaks internally, the coolant will often contaminate the oil, and the coolant can enter the car’s combustion chamber.

When this occurs, there will be little to no coolant left in your reservoir, causing your engine to overheat.

11. Coolant Leaking Externally

Similar to an internal coolant leak, an external coolant leak can cause your engine to overheat, and external coolant leaks are easier to spot.

Generally, an external coolant leak can appear in various places, such as the radiator, hose, water pump, thermostat, etc.

12. Bad Cooling Fan

Your car relies on the airflow that comes from the radiator to reduce the coolant and engine temperature while it is being driven.

In other instances, such as when your car is idling, your car will rely on a cooling fan to keep the engine cool.

As such, a faulty cooling fan will lead to an overheating engine while you idle because nothing is cooling the engine.

13. Dirty Air Filter

Your car has air filters that keep debris, sand, insects, particles, etc., from reaching the engine while your engine sucks in air.

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However, air filters can get dirty over time, which can lead to an overheating engine if you ignore the air filters.

Dirty air filters will create restricted airflow, which will strain the fan motor in the air handler, causing the motor to burn out and make the engine overheat.

Also, if your air filters are in good condition, you can wipe them clean, but damaged air filters will need to be replaced.

14. Failing Drive Belt

If you have a failing or loose drive belt or serpentine belt, it could be a reason why your engine is overheating.

Normally, a loose or failing drive belt will cause other mechanical issues, such as making your water pump perform poorly.

As such, a drive belt that makes your water pump ineffective will lead to your engine overheating.

15. Faulty Heater Core

Your car has a heater core that functions as a small radiator that will use the hot coolant from your engine to warm the cabin.

However, the heater core can get plugged up, which will compromise the flow of coolant to the engine, which will make the engine overheat.

Additionally, a heater core can have a leak, which will mean there will be little coolant in your engine, leading to an overheating engine.

Generally, it is more common for a heater core to leak than to be clogged up, as it is harder for debris to enter the heater core.

To know more, you can also read our posts on why your check engine light is on, why your truck shakes when parked, and why cars backfire.

Conclusion

Normally, an engine will overheat because of an issue with the coolant, such as an internal or external coolant leak, a lack of coolant, or using the wrong type of coolant.

Also, other issues within your car’s cooling system can make your engine overheat, such as a faulty radiator, cooling fan, or heater core.

In rarer circumstances, extreme heat from the outside weather can make your engine overheat, especially if there is already a problem with your engine’s cooling system.

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