What causes a car to heat up when it's not running?
My car seems to be running well, but I am worried that it can get hot when idling.When I am stopped in traffic, the temperature gauge goes up.It cools down when I drive again.Should I be concerned about the car overheating while idling?
There are a number of different problems that you might be dealing with if you have a overheating car.The most likely reason for this type of problem is that your fan isn't working, but the reason, and the fix, will differ depending on the car you drive.
Low coolant, air in the cooling system, a bad temperature sensor, and even a faulty gauge are some of the causes of intermittent overheating.
Depending on your problem, turning on the A/C or cranking up the heat may help roll back the temp gauge.The image is courtesy of Harry Heng.
When the engine is running or after you shut it off, some things cannot be checked.When the engine is still hot, don't check your coolant level.
The last thing you want is to be stuck in traffic when your car is overheating.The image is from the Creative Commons 2.0 website.
It might be helpful to understand how the cooling system works if you are driving down the road.The heat is exchanged with the air through your radiator.The water pump allows the engine to run at an appropriate temperature when the coolant is constantly cycled through.
When your car is moving air is forced through the radiator to get more heat.It is easy to see how this works when you stick your hand out the window of a moving car.
When your car is not moving, the radiator isn't as efficient.A fan helps things along.The principle is the same whether the fan is driven by a belt or electric.
Even though the engine isn't working as hard when you're idling, it takes more work to get the heat out of the car.This type of problem is usually caused by the fan not doing it's job, but it doesn't hurt to check other things first.
It is important to not let your engine get too hot.If you notice that it gets dangerously hot at idling, you should avoid driving in stop and go conditions until you can check it out or take it to a qualified technician.
There are a few things you can check after being stuck in traffic.Before you go poking around under the hood, it is important to let your engine cool down.The cooling system needs to be depressurized if you want to check the level of the radiator.
If the hoses are particularly hot to the touch, or feel taut when you squeeze them, that is a sign that you could be in for a lot of trouble.
You can remove your cap when it is safe to do so.If the coolant isn't all the way to the top of the fill neck, top it off with the appropriate type of antifreeze.You can get a good idea of which type to use by looking at the color of the coolant.
In some cases, the fill point is an overflow bottle.If you look at the side of the bottle, you may be able to see if the coolant is full.When it gets hot, the coolant expands so it may look full until it cools down.
It is not something to be aware of when dealing with the mixture of water and antifreeze.The reason is that it isn't as good at transferring heat as it is at not freezing.If you mix it with water, you will get the benefit of not cracking your engine block.
If someone replaced your coolant with a very strong mixture of antifreeze, it could potentially cause your overheating problems.Ten bucks is a good price for an antifreeze hydrometer.
Adding straight water and draining some of your antifreeze mixture may be able to fix your overheating problem.
Many cars that have a longitudinal engine use belt-driven fans, which essentially means that a fan is mounted to a pulley that is driven by an accessory belt.You can see this when you open your hood, since there is a big fan between the engine and radiator.
If your engine is running, your fan may be bolted straight to a pulley.It will be mounted to a fan clutch that only engages when needed.
The easiest thing to check is the fan belt.If it is loose, tighten it to fix your problem.If the belt is missing or damaged, then you should replace it and tighten it up, unless there is another underlying problem like a pulley.
The fan clutch bolts or screws to a fan pulley or water pump and allows the fan to engage or disengage.The image is courtesy of lw5315us.
The situation is more complicated if your car has a fan clutch.If the fan clutch isn't engaging when it needs to, that could be the reason that your engine is overheating.
The fan clutches are either electric or thermal.If your car has a thermal fan clutch, you can check to make sure it is plugged in and that the wires are not damaged.The wires could be damaged if the plug is disconnected.
Electric radiator fans are used in some vehicles with longitudinal engines.The fans are mounted on or near the radiator and are designed to switch on when there isn't enough air in the room.
If your engine is overheating, it is easy to tell if your electric fans are working or not.That is the problem if the engine is overheating and the fan isn't on.There is no power to the fan or the electric motor is burned out.
The electric fans are bolted to the radiator.The image is courtesy of David Brodbeck.
Turn on your air conditioning and see if you can test the operation of your fan.This will cause the fan to kick on.There is a problem if the fan doesn't turn on.
If the fan is plugged in, it's the easiest thing to check.It could be the problem if it isn't or there is damage to the wires.There could be an issue with your car's onboard computer.
You might want to check for power if you can safely access the fan power connection.Replacing the fan if it isn't on will be a pretty safe bet.
If you can't figure it out on your own, then you need to have it checked out.If you are stuck in traffic with no escape in sight, you may be able to bring the temperature down temporarily.
The electric fans may be forced to turn on if the A/C is turned on.Forced the fans to turn on may make up for the additional load on the engine.In some cases, turning on the heat may help.The reason is that your heater core is a small device that transfers heat from the outside to the inside of your car.When you turn on the heat, you get heat from the coolant.It may be enough to keep your engine from overheating so you can get to a shop.
He's no stranger to the inner workings of modern automobiles, as he worked in the north end of Seattle for a decade.He has been a writer for Lifewire.com since closing his shop in 2007.