How to Fix an Overheating Engine

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It’s the last thing anyone wants to see on their dashboard — their temperature gauge slowly creeping into the red, while lights start to flash across the console. If your engine is overheating, that means your car is sidelined until you can fix it. How can you repair an overheating engine, and is it something you can do at home?

What Causes Engines to Overheat?

Your engine maintains a lower operating temperature by the cooling system, which includes hoses, a radiator, a thermostat and various sensors that report to the engine control module, the computer under your hood. Any failure in any one of these things could cause the engine to overheat. Let’s take a closer look at three of the more common causes of cooling system failure.

1. Failed Thermostat

The thermostat is a simple switch that reacts to heat. When the engine is cold, it remains closed keeping the coolant in the engine. As the engine heats up, the thermostat opens and allows the coolant to flow into the radiator. If the thermostat is stuck closed, it can cause your engine to overheat because the refrigerant is trapped in the engine.

Swapping out a thermostat is pretty easy. Just remove the upper radiator hose, remove the thermostat housing, replace the thermostat and the gasket that sits between the housing and the engine block and replace the housing and hose. Thermostats, in most cases, will cost you less than $20.

2. Lack of Coolant

While your engine is cold, take a look at your coolant reservoir. If you don’t have enough coolant in your engine, it will overheat because there isn’t enough liquid to carry the heat away from the combustion chamber. The source of the leak might be obvious — especially if you’ve found puddles of antifreeze under your car as it cools — or it might be internal. If there are no apparent leaks, check your oil. White or milky oil is a sign that you’ve blown your head gasket and the coolant is leaking into your engine oil.

If there are no detectable leaks, you have enough coolant in your radiator and the engine is still overheating, you can also try including a coolant additive the next time you fill up your radiator. These lower the running temperature of your coolant, making your engine run up to 10 degrees cooler, preventing overheating.

3. Internal Clogs

Just because your radiator looks okay on the outside doesn’t mean the coolant is flowing freely. If the coolant can’t move, it’s going to continue to pull in heat until it can flash-boil inside your engine, doing damage to the cooling system and venting all your antifreeze.

Clogs can be small or large and can appear anywhere in the cooling system. The most common clogs are found in the radiator, as well as in the hoses that move the fluid too and from the engine block. This problem can be an easy fix. In many cases, all you need to do is flush out your cooling system with a regular garden hose. Radiator flush can also help because it adheres to the particles that can gather together and create clogs.

If flushing your radiator doesn’t work, you may need to resort to replacement instead.

Don’t panic if your car starts to overheat. Start by pulling off to the side of the road and shutting off the engine. Try not to drive it until you’ve figured out precisely what is causing the problem. Driving a car while it’s overheating can cause damage, and most cars will shut off automatically if the engine temperature climbs too high.