In a car engine, multiple metal parts rub against each other at high speed, creating a lot of heat. If heat production isn’t controlled somehow, the temperature will quickly rise beyond the normal operating temperature, leading to engine seizure in a jiffy. To ensure engines stay cool and last as long as possible, car manufacturers invest large sums of money to design the most efficient cooling systems.
Unfortunately, as soon as a component fails, the system will be quickly overwhelmed by the heat. When it happens, it’s vital to react correctly to prevent extensive damage to the engine’s internal components. Since time is of the essence when an engine runs hotter than it should, here’s a brief overview of why your engine might be overheating and what you need to do to keep the repair bill as low as possible when it occurs.
Common Reasons Why Your Car Might Be Overheating
The cooling system in your car is a sophisticated group of parts working in unison to prevent your engine from overheating. Your car’s system works by pressurizing a coolant and water mixture and circulating it through the engine and into the radiator using a pump. Heat is extracted from the coolant when air passes through the radiator’s cooling fins.
A car may overheat for a variety of reasons. Any of the key components in your cooling system can fail and invariably result in your engine running above the normal threshold.
Coolant leaks
Cooling systems leaks are pretty frequent and may lead to multiple problems. For starters, the cooling system on your car is a closed system, meaning that the coolant level shouldn’t decrease. It can sometimes evaporate slightly, but a significant decrease often indicates a leak. If your car leaks coolant, your engine will risk overheating once the coolant level is low enough.
Furthermore, cooling systems also need to be pressurized to work efficiently. Liquids boil at a higher temperature when pressurized, and cooling systems use this property to their advantage, allowing the coolant/water mixture to reach a vehicle’s average operating temperature without boiling. If there is a leak in the system or the radiator cap doesn’t seal correctly anymore, the coolant will most likely start to boil. It won’t be able to dissipate heat, and the temperature will rise uncontrollably.
And that’s not good at all…
Mechanical Problems Leading to Overheating
Various mechanical problems can also cause the cooling system to fail. The most common reason, and also the least expensive one to repair, is a faulty thermostat. With time, thermostats tend to stay stuck in the closed position, preventing the coolant from circulating into the engine’s water passages. A clogged radiator or heater core will also cause the same problem.
A defective water pump will also prevent the coolant from moving around. When it happens, it’s sometimes possible to see coolant coming out from under the water pump. Unfortunately, replacing a water pump is often quite costly because of the extensive work required to access it.
There are also more severe reasons for overheating. A cracked or blown head gasket will allow the coolant passage to communicate with the combustion chambers or oil passages, and oil may contaminate the coolant. When they rise, pistons can also create excessive pressure in the system leading to ruptured hoses and large coolant leaks.
Radiator and Heater Hoses
All cars have two large hoses running from the water pump to the radiator and from the radiator to the engine. Since both are made of rubber and since rubber tends to dry out and crack with time, it’s common for these hoses to crack and leak.
Two smaller hoses also run to your car’s interior and connect the heater core to the rest of the system. If they start to leak, you should be able to see coolant under the right side of the dashboard.
You should also look for leaking hoses near the intake manifold on the top of your engine. Car engines typically have several small hoses to channel coolant to the intake system. These hoses become brittle over time and can start to leak.
Broken Belts and Faulty Pulleys
Your engine will have at least one belt driving the water pump. The drive belt may also power the cooling fan on older car models, which is why it’s sometimes called a fan belt. Like rubber hoses, rubber belts also dry out and break with time.
A common component that fails is the tensioner pulley. Its job is to apply a specific tension onto the drive belt. When the tensioner pulley’s bearing wears out, the pulley might seize and break the belt.
Electrical Problems Causing Overheating
Most of today’s vehicles use electric fans instead of a fan driven by the drive belt. However, the cooling system on most vehicles is efficient enough to cool down the engine when driving under normal conditions. The cooling fan is then only used when idling for a long time or in extreme heat conditions. If your engine only overheats when idling, that might be your problem.
Cooling fans have fuses that can blow up when too much electrical current passes through, which typically happens when a fan motor is about to seize or has a short-circuit. If your fan’s fuse is blown, make sure to find what caused the problem in the first place before actually replacing the fuse.
To troubleshoot and repair an electrical problem, you’ll need to get your hands on your car’s cooling system electrical diagrams. Even though such diagrams can sometimes be found on the internet, the safest bet is usually to get a digital copy of your car’s repair manual. Everyone knows that the information and data found on Google are not always accurate, to say the least. Just play it safe and get a quality repair manual instead.
Getting an Overheating Car Off the Road
If your engine is overheating, you must stop driving as soon as possible. Your engine will, without a doubt, fail if you continue to drive with an overheating condition. You should immediately stop your car in a safe place before trying to figure out why it is overheating.
The first thing you should do is figure out if the problem is something you might be able to fix. Open your hood and inspect the engine bay for leaks. Can you see steam coming out from somewhere? If you have a leaking radiator hose, you may be able to make a temporary repair to get home. Duct tape can sometimes do the trick if you aren’t far from a repair shop. If the reason your car is overheating is serious, like a blown head gasket, you will need to have your vehicle towed.
Sometimes, you may be able to use some tricks to solve problems that cause overheating. If the small hoses on the intake manifold start to leak, for example, you may be able to use a piece of heater hose to replace the leaking one. Then, connect one of the heater hoses from the water pump to the other heater hose fitting at the intake manifold. You will not have a heater, but you’ll be able to get your car home.
It is important to remember that you should never pour cold water into a hot radiator. The temperature difference can cause rapid thermal expansion that can crack your engine. Instead, keep the key ON to keep the fan blowing. Turn on the AC to start the second fan too. You can also cool off a hot radiator by spraying it gently with running water.
Wait until the engine is cooled, start the vehicle again and keep your eye on the temperature gauge. If the temperature begins to rise over the standard value, stop the car again and have it towed.
Frequently Asked Questions (FAQs)
Can a bad PCV valve cause overheating?
No — a bad PCV valve does not cause overheating.
Since unburnt air/fuel gas passing the piston rings and landing in the crankcase/oil pan creates excessive and potentially damaging pressure, the PCV’s job is to recirculate the fumes back into the cylinders so it’s appropriately burned and processed by the vehicle’s emission system.
A bad PCV valve will usually stay open, allowing excess air into the cylinder, and causing a lean air/fuel mixture, which can surely be a concern but won’t make your vehicle overheat. A bad idle, engine surging, a check engine light coming up, or sudden oil leaks are common symptoms of a bad PCV valve — none of them, however, leads to overheating.
In Brief
An overheating car is a very stressful situation. The best thing you can do is to let the engine cool off before testing it again. If the problem comes back, get the car safely somewhere you’ll be able to investigate further. Most cooling system problems are pretty easy to diagnose and fix, even though some conditions may be harder to troubleshoot than others. In all cases, make sure to get your hands on your car’s repair manual and follow the manufacturer’s recommended troubleshooting procedures. When in doubt, you’re sometimes better off asking a trustworthy mechanic for advice. When dealing with a car’s cooling system, the last thing you want to do is to eyeball it and half-ass a quick repair. Never forget that fixing it right the first time is always the best way to save on car repairs.
Good luck!
