Overheating engine can be a frustrating thing and drivers can try all kinds of different recommendations from the internet to cope with the problem. One of the very common things you can find in forums and some blogs is to turn on the AC to cool the engine. But does it actually work?
In short, running the AC will not cool the engine and even vice versa – it will make the engine work harder and heat up even more because of extra loads on the alternator. The fact that AC produces cold air is only true for the interior but in the engine bay, it will only cool one small aluminum pipe that connects the AC radiator with the interior of your vehicle.
So, no, it doesn’t make sense to turn on the AC to cool the engine. But I want to give you a more detailed overview of the problem.
Here’s what I will cover in this article:
- Can running AC somehow affect the engine temperature?
- Should you turn on the AC when the engine is overheating?
- How can you cope with the overheating engine in your car?
- Can you drive further if the engine is too hot?
Does AC affect the engine temperature somehow?
I don’t know where this myth started but it became like an infection. I personally knew some guys who turned on the AC in their vehicles once they saw that the engine temperature gauge showed overheating. This is the most counter-efficient thing you can do, in this case.
Actually, your AC does affect the engine temperature but it only makes it hotter. Here’s how it works:
- once you turn on the AC, the air-conditioner compressor activates and starts pumping freon;
- the AC compressor is driven by the drive belt that also drives the alternator and other equipment under the hood of your car;
- to drive the compressor, the engine needs to produce more power and this puts some more load on the engine;
- as a result, the natural heat is produced even faster than if you didn’t turn on the AC;
- also, the AC radiator cools the heated freon and changes the way the engine cooling system radiator works.
In the end, you get more heat produced in the engine than before. Also, this will change the gas mileage because now the engine will start rotating the AC compressor which is not that easy to do. The compressor takes a lot of power from the engine. That’s why, if your engine is not that powerful, you will actually feel that it lost some power and now doesn’t accelerate as fast as before.
So, yes, the AC in your car can affect the engine temperature. But it won’t cool the engine down. It will only add some heat to the engine bay making it even harder for the engine to survive when it’s overheating.
When can turning the AC help cool the engine?
The answer is never. Turning on the AC will only make things worse and heat up the engine even worse. I described the reasons before. Actually, if you see that the engine is overheating, it’s important to try and relieve stress from the engine by turning off everything that loads the alternator and other units connected to the drive belt.
What should you do if you see the engine overheating?
If you find that the engine overheating, it’s important not to ignore this problem. Your first task is to prevent the engine from failing and the second important task is to understand what is wrong with the vehicle and what you should do.
Here’s what to do in the first place:
- Stop the vehicle and turn off the engine. This will at least prevent the engine from failing and will obviously help you save the unit.
- Open the hood but don’t touch the engine or radiator. With the hood open, the engine will cool down much faster.
- Look at the coolant level. It’s quite obvious that you should check the coolant level in the reservoir. But don’t open the reservoir till the engine is cool!
- Locate any coolant leaks. Maybe, you will see some coolant leaks that will explain to you why the engine was overheating.
- Turn on the ignition and see if the check engine light stays on. If it does, you should read the codes with the scanner or plan a visit to a trusted repair shop.
Unfortunately, you can’t check the thermostat or the water pump right on the roadside. But if you have the OBD2 scanner, you can see the codes in the ECU and decide what is wrong with the car. Even the cheapest scanner may help because it will show you the code and then you will be able to google it and see what it means.
What can cause sudden engine overheating?
There are numerous problems that can cause engine overheating in your vehicle. While the most common ones are thermostat failure or low coolant, there also can be problems with the water pump, blockages in pipes, low efficiency of the coolant, etc.
Also, the engine may start producing more heat. And this is another problem you should consider. In this case, the engine may be poorly lubricated, worn out heavily, or even at the edge of dying.
But sometimes, overheating may be just because of the too-hot weather and difficult driving conditions. For example, driving in a traffic jam may cause overheating because the air doesn’t cool down the engine coolant radiator.
If the reasons for engine overheating are not clear at once, you should visit the repair shop and have the car inspected. Usually, it’s not that hard to find the actual reason and repair the engine so that it didn’t overheat anymore.
Can you still drive if the engine is overheating?
It depends on how badly it is overheating. If the temperature is 10% higher than the normal working temperature, you may keep driving but keep an eye on the gauge to stop the vehicle once the temperature goes higher.
Actually, it’s recommended to stop your car immediately in those cases only when the engine temperature is in the red zone of the temperature gauge. But I wouldn’t wait that long. I would stop my car and turn off the engine if the temperature is 20% higher than normal.
There are some negative things that may happen with an overheated engine:
- it may wear really quickly because of bad friction;
- it will heat even faster once the friction becomes abnormally tight;
- there may be scratches in the cylinder block;
- at a certain moment, the engine may get stuck and this will be a huge problem;
- overheated engine head may change its shape a little and this will turn into a disaster;
- overheated oil is not viscose enough to lubricate the engine, it becomes much less efficient;
- overheating may lead to slow or quick engine death depending on your situation.
The consequences may be disastrous. So, if you see the engine overheating, you should stop the car and turn off the engine. This is the only right way to act in this situation. Let the engine cool down and then you can drive until you see the needle in the temperature gauge going up again.
It doesn’t mean you need to call a tow truck and spend a lot of extra money. But you obviously need to let the engine cool down before you continue driving. If the engine overheats again, you should plan your visit to the dealership or to the repair shop to have the car inspected and repaired if needed.
Final thoughts
So, the AC will obviously not help you cool down the engine. It will only make it produce more heat and put more load on the poor engine. If you see the engine overheating, you should stop the car and try to figure out what’s happening. Even if you can’t locate the problem, just let the engine cool down and then drive further. But don’t let the engine overheat to more than 20% over its working temperature.