Who isn’t instantly frustrated and anxious when they notice their temperature gauge climbing towards the red zone? Odds are, you’ll find yourself asking “Why Does My Car Overheat?”
Today, we’re out to answer exactly that question!
First off, a word of caution. If you are in a vehicle that is overheating, do not try to drive farther. Pull over, stop driving and turn the vehicle off. Actions can be taken to assess any issues, though the best course of action is to have the vehicle towed to your mechanic of choice.
The Cooling System
Here’s what happens when the engine is cold
A cold engine isn’t ideal since fuel doesn’t vaporize as well at cold temperatures. Additionally, the oil is thick and sluggish when cold, so it can’t circulate through the engine as well as it should. So, it needs to heat up – fast.
Believe it or not, the cooling system is designed to help. The moment you start the car, the water pump begins to propel the cold coolant from the lower tank in the radiator (basically, the bottom section) to the cold engine block. From here it travels through channels in the casting to the cylinder head, and then back towards the pump.
Now here’s the clever bit. Located close to the pump is the thermostat. If the coolant is too cold, the thermostat remains closed, preventing it reaching the radiator and causing it to be pumped straight back to the engine uncooled, as well as around the cabin heater.
The coolant begins to warm up very quickly, helping to carry heat around the engine and accelerating the warming-up process, so improving the engine’s efficiency.
Here’s what happens when the engine is hot
An engine’s maximum operating temperature is around 250 degrees Fahrenheit but when the coolant reaches around 195 degrees, the thermostat opens, diverting the hot coolant to the radiator via the upper radiator hose and into the upper radiator tank.
Wax inside the thermostat melts and expands, pushing it open. Incidentally, this change in temperature is being monitored by a sensor that relays the data to the car’s engine control unit, which makes small running adjustments to the fuel and ignition systems as necessary.
On the latest cars, the operation of the thermostat is controlled directly by the engine’s computer. No more thermostatic wax. This allows a more precise control of the coolant temperature, further reducing emissions and increasing efficiency.
Why Does My Car Overheat?
As you can see, there are quite a few parts to your car’s cooling system working together to keep the engine around it’s optimal 195 degree temperature. If one of those parts fails to do it’s job correctly, overheating is usually the result.
The most common cause of overheating is a low coolant level due to a leak that went unnoticed for a period of time. if your cooling system doesn’t have enough coolant, it won’t be able to work as effectively. This, in turn, will cause the temperature of the engine to rise. We recommend checking the coolant levels regularly, since it’s easy to take a quick look while you’re checking your oil or refilling your wiper fluid.
The next most common cause is a faulty thermostat. The thermostat controls the flow of the coolant. When your engine is just starting, the thermostat valve stays closed, and the coolant doesn’t circulate. Once the engine reaches operating temperature, the valve will open and coolant will begin to flow through the engine. A faulty thermostat might remain closed even when the engine is hot, which can quickly lead to overheating.
The third most common cause is a faulty radiator fan. The air that flows over the radiator helps remove the heat that the fins have grabbed from the coolant, but air only does that when your car is moving. So, when your vehicle comes to a stop, the radiator fan will kick in. This fan moves air across the radiator. If it’s broken, your car may begin to overheat when it’s idling, only to cool down again once you start moving.
These aren’t the only possibilities, though. A blown head gasket, faulty water pump, clogged radiator, and even dirt & debris in the radiator’s cooling fins can all lead to an overheating car. As we mentioned earlier, if you notice that temperature gauge start to climb, pull over and assess the situation!
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