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How to Diagnose Why Your Car is Overheating

How to Diagnose Why Your Car is Overheating

This article examines the causes for a car to overheat and relates what various symptoms point toward.

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A car that is overheating is a cause for alarm for most drivers. Thoughts of cracked heads and engine blocks begin to swirl through your mind. The fear of being stranded and having to pay high towing and repair bills lurk omenously. In many cases, if you pay attention to the symptoms, you can diagnose the problem. This will allow you to decide whether to tackle the job yourself or head to the mechanic. Here is a list of the most common causes of a car to overheat.

The coolant level is low.

In hot weather, the coolant in your engine can become low due to evaporation through the overflow reservoir. As hot coolant is pushed into the reservoir, a certain amount of steam is produced. Over a long time, this can lead to lowering coolant levels in the system. It may also be that the system was not filled properly after the last cooling system repair or maintenance. This is easy to diagnose. Remove the radiator cap when the car is cool and look at the fluid level.

You have a leak in the engine cooling system.

Leaks can occur in a car’s cooling system in a variety of ways. The radiator or heater cores can become old and develop pin holes that leak coolant under pressure. Likewise, radiator and heater hoses become weakened by the high pressure that they sustain until the hose ruptures and leaks coolant. Just before the water pump fails, it will often leak cooling fluid from the weep hole on the bottom of the pump. Cars have a freeze plug in the engine block. This plug sometimes fails and allows fluid to escape. There are also a few places around the engine where gaskets can leak coolant. These leaks are usually either diagnosed immediately when the hood is raised while the car is hot, or antifreeze will be found on the ground under the car when it is parked.

The thermostat is bad.

Most of the time when thermostats fail, they fail to open. This means that the thermostat acts like a plug in the cooling system and keeps the antifreeze from circulating through the radiator to cool down. The result is that the vehicle overheats. When there are no system leaks and the water pump is not bad, the culprit is usually the thermostat.

The water pump is failing.

If the water pump does not circulated the coolant, your car will overheat. Water pumps usually signal their impending demise. Most water pumps will emit a high pitched squeeking sound that is hard to miss. When you start to hear the squeek, you will only have a few days to fix the problem or risk being stranded. The second symptom is the water pump starts to leak fluid from the weep hole at the bottom of the pump. This is a sign that the internal seal is failing. When this sign shows up, get the car fixed quickly because it will continue to get worse.

Your cooling system has trapped air.

This one can be a little hard to diagnose. Some cars have a bleeder on the thermostat housing that can be opened to release the trapped air. Most of the time trapped air is the problem when the car overheats within a short time of a major cooling system repair.

The radiator cooling fan is not working.

Check for this problem by starting the car and turning the air conditioner on while the car idles. The cooling fan should come on within a short time of enabling the air conditioner. If it does not come on, you need to make a repair. This repair might be replacing the fan. You may also have a cooling fan relay that has failed. The third possibility is a blown fuse other electrical problem.

The radiator core has become clogged.

This is a problem for older and high mileage vehicles. Oxidation, scale, and sludge can conspire to clog the radiator core. It can even be the result of adding too much stop leak to the system. Using a good quality radiator flush in the cooling system may help, but probably you are headed for a radiator replacement.

Your radiator cap needs to be replaced.

A bad radiator cap can make you feel stupid in a hurry. Without a radiator cap pressure tester, it can be quite difficult to diagnose. If your radiator is spilling fluid around the cap as soon as you stop the car when it is overheating, you have found the problem. Unfortunately, this is not the usual symptom of a bad cap. If you have a shop or parts store in town with a cap tester, take it in and have them check it for you.

You have a blown head gasket.

You usually do not have to wonder about this one. Huge plumes of white smoke billowing from your exhaust pipe will tell you that coolant is pouring into your car’s cylinders. If it leaks to the outside, you will see puddles of coolant under your car that are not located near anything that should leak. In extreme cases, the car simply will not start after you have turned it off when it is hot.

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