Saturday, April 13, 2024

Why does my car overheat when the heater is on?

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Let’s say you’ve been driving your car for a while now. You turn the heater on to keep away from the cold weather – and then, your engine suddenly starts overheating.

This makes your car smell funny and damages your engine whenever your heater is on.  If you’re experiencing these issues, it’s time to check your car’s coolant system.

It’s important to eliminate any burdens your car systems have. Issues with your coolant levels and, excessive dust found in the air filters of your car – make your car overheat.

When not cleaned often, dirt puts pressure on your car system and, heats the coolant in your car. This can permanently damage your car if left unattended for too long.

The inner parts of your car could be causing overheating issues too. The valves of your engine won’t allow for proper combustion to occur if it’s clogged or damaged.

All these issues make it harder for your car to function properly. As a result, your car starts overheating when you turn the heater on.

It’s time you take a look at why your engine overheats when you switch the heater on, and what you can do to prevent it:

The Reasons For Car Overheating When Heater Is On

The top reasons for car overheating when the heater is on:

  • Clogged & Damaged Car Systems

This is a very common reason that your car is underperforming. It’s time to check the filters of your radiator, fuel tank, A.C., cabin filter, etc for any possible debris on them. Any issues that arise because of clogging or excessive dirt on your car’s filters – need to be cleaned.

  • Bad Thermostat

Your car overheats because of the dysfunctional thermostat it has. When you notice that your thermostat is stuck, it stops the coolant from successfully reaching the radiator. This causes problems with your car engine – and raises the temperature of your car.

  • Valve Problems

When there are valve clearance issues in your car, it causes your engine to start performing at lower levels. The valves of your car should be at an optimal level – with not too much or too few gaps in the tops of the valve stems. It’s advisable to check your valve clearances every 15,000 miles to stay on the safe side.

  • Less Engine Oil & Coolant Level

Drops in the level of oil or coolant in your car will cause major overheating issues. This is because your car needs a certain level of lubrication to function optimally. When it doesn’t get the required amount of liquid level it needs, it gets hectic for your car to perform its best.

  • Dysfunctional Car Fans

The cooling fans of your car – such as the ones in your radiators, are responsible for keeping your car at a suitable temperature to function properly. When they don’t work well, it could be because they are damaged or worn out.

This is a serious problem and requires immediate fixing, or it can permanently cause car damage.

  • Leaks & Pump Issues

The leaks in your car prevent it from maintaining and moving coolant – at required levels throughout the systems of your car. Any leakage or pump issues make your car overheat and cause smoke to come out – if too damaged or left unfixed for too long.

  • Car Sensor Problems 

The sensors in your car – such as ECT & FTC sensors can make it harder for your car to reach an optimal temperature and makes your engine fail. This is because it makes the fans of your car function poorly, and your engine doesn’t stay cool.

Ways To Prevent Car Overheating When Heater Is On

  • Maintain Oil & Coolant Levels

Topping up the coolant and oil levels at required intervals makes it easier for your car to function smoothly. It also reduces the amount of pressure your car exerts to work. For your car to drive swiftly, you need to fill up its fuel and coolant levels often.

  • Clean Car Often 

It’s important to keep your car clean for it to work properly for a long time. The inner parts of your car need to be cleaned as much as the outside. A dirty car that’s filled with debris only wears your car down. Not only does your car underperform, but you can feel your car dragging when you drive it.

Therefore, you can either get your car cleaned by professionals – or give it a quick clean often.

  • Fix Any Leaks Or Pending Repairs 

If your cooling system has leakage, it results in car overheating. This can cause major drivability issues and stop your car from working. Any repairs your car may have – especially repairs for its cooling & water pump system, radiator, engine, etc. need to be attended to immediately. Leaving repairs for too long can cause long-term car problems.

  • Keep an Eye On the Temperature Gauge 

Never let your temperature gauge go too far ahead either on the cold or hot side. Ideally, its needle should be pointing at the center. This shows that the temperature of your car is at optimal levels. It helps you keep an eye out for overheating issues before they occur.

  • Don’t Overwork Your Car 

When you drive your car for too long or it stays in hot weather a lot, it causes car overheating. Even when your car has pending repairs and, you keep using it without fixing them – it not only causes overheating but also makes damages your car permanently.


When you notice that your car has started overheating, it’s important to prevent putting any further pressure on it. Getting it checked soon will help you prevent major repairs in the long run. And, if you want your car to work for a longer time – regular maintenance is key.

Keeping coolant levels in check, tanking up fuel at required intervals, and cleaning your car often – will help you prevent it from major overheating in the long run, especially when you switch your car heater on.

Your engine is sure to get damaged if your car overheats for too long. In that case, getting a replacement would be necessary. Check out budget-friendly used engines for sale for your car today – select from the largest inventory in the U.S.

Premium quality and mechanically tested used engines and transmissions available- with warranty & 100% ASE Certification. Contact us now- tel:1800-518-9776

Frequently Asked Questions

Why does my car overheat when the heater is on?

A problem with the airflow in the engine of your car makes it overheat when the heater is on. A good amount of heat needs to exit the car engine, or it causes immense overheating that damages your car.

Can a heater core cause overheating?

Yes, a heater core causes your engine to overheat. This is because your heater core may be defective. It’s important to check the gaskets and if any repairs are needed, it needs to be repaired soon.

Why does my car overheat but the heater blows cold air?

When your car overheats while your heater blows cold air – it means your coolant levels are at optimal amounts in your car. The problems are with the inner parts of your car. Cleaning air filters regularly helps air flow and greatly reduces overheating.

How can I prevent my car from overheating when I use the heater?

You reduce your car from overheating – clean all the air filters of your car often. It’s important to also get the pumps checked. This helps in lifting burdens from your car engine and helps it work faster while maintaining good airflow.

How do you temporarily fix an overheating car?
There are a few ways you can temporarily save your car from overheating:

1. Save your car from the sunlight
2. Maintain coolant and oil levels
3. Clean all existing air filters and pumps.
4. Fix any faulty leaks.
5. Check on your car often.

Why would my car overheat but my heater blows cold air?

Your car overheats but your heater blows cold air because of your coolant. When the coolant levels in your car are at an optimal temperature, it keeps your heater cool. The overheating in your car, in that case, is due to other inner car part problems.

Does the heater pull heat from the engine of my car? 

The heat that comes from your radiator can make your engine hotter. It’s best to let any hot air out from your car engine – and let it cool down for a while.  Temperature lowering can save your car from overheating, and combustion.

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