Heat is an engine’s biggest enemy. The damage caused by overheating can be catastrophic and may require an expensive repair if the problem is not caught in time.
During the hot summers of today, coupled with ongoing construction going on in various areas of Karachi, traffic jam has become a normal occurrence. Massive traffic jams are observed in several areas of the city on daily basis and sight of cars stranded on the side of the road with the hood open and smoke billowing out due to engine overheat is a pretty common sight.
It’s better to know what exactly causes the engine to overheat and what can be done to prevent your engine from overheating.
What is overheating?
An engine operates efficiently at a certain temperature. That temperature, even though it is too hot to touch by hand, is significantly cooler than it would be without a cooling system. Overheating is when the temperature of the engine climbs to a point where mechanical damage can occur. Steam coming from the engine bay, a temperature gauge reaching the red zone, and engine warning lights on your dashboard are signs that your vehicle may be overheating.
The cooling system
Regardless of displacement, every engine has a cooling system. Modern vehicles are equipped with a cooling system that circulates coolant throughout the engine and through a radiator to dissipate the heat.
Cooling system in a vehicle consists of many components including a water pump, a thermostat, a heater core, a radiator, coolant hoses, and the engine itself.
How it works?
The water pump has an impeller that circulates the coolant. The impeller is like a fan or windmill, and is turned by the serpentine belt, or chain. The coolant flows through the engine’s coolant jacket, which is a labyrinth of channels through the engine block. Heat is absorbed by the coolant and carried out of the engine into the heater core.
The heater core is a small radiator inside your vehicle to warm up the interior. A valve controls how much hot coolant passes through the heater core to warm the air temperature inside. The coolant then passes through a hose toward the radiator.
The radiator is essentially a long tube that is bent into shorter coils. The air passing by the coils disperses the heat from the coolant inside, reducing the temperature of the coolant. After passing through the radiator, a hose carries the cooled fluid back to the water pump and the cycle starts over.
Why an engine overheats?
There are several causes of overheating. Almost all of them roots from the lack of coolant circulation but can be caused in different ways.
Cooling system leaks
A leak in the cooling system doesn’t directly cause the engine to overheat. The direct cause is air entering the cooling system. When a leak is present, the coolant level drops and air is sucked in and circulated. Air is obviously lighter than coolant, and once it rises to the top of the cooling system it causes what is known as an airlock. An airlock is a large bubble that can’t be pushed through the cooling system by the coolant flow. That means that cooling system effectively stops circulating and the coolant remaining inside the engine becomes super-heated.
A blockage in the cooling system is another indirect cause, as overheating is actually due to a lack of coolant circulation inside the engine. When the cooling system is blocked and the coolant can’t circulate to the radiator to disperse heat, the engine overheats. A few common of obstructions are:
- A thermostat that doesn’t open when it should.
- A mineral deposit blocking the radiator.
- A foreign object inside the cooling system.
Water pump malfunction
A water pump failure is one of the more regular causes for overheating. The water pump is the most active component in the cooling system and is responsible for maintaining coolant circulation. Over time, the bearing or impeller inside the water pump can wear or break, and the impeller will no longer turn. When this occurs, it’s usually a short time until the engine overheats.
The coolant isn’t concentrated enough
One of the important reasons is the fact that most people use plain tap water instead of coolant which is a very bad idea itself. Water boils at around 100° C (212° F) and has the tendency to evaporate at high operating temperatures, thus with no liquid left within the cooling system the engine quickly overheats. On the other hand coolant will begin to boil between 240° C and 270° C and since it doesn’t easily evaporates means it stays in the cooling system while keep doing its job.
Old/ substandard engine oil
A lesser known system that assists in cooling the engine is the engine oil itself. It plays a large part in engine cooling and also in preventing excessive temperatures from building up. The engine oil lubricates internal engine parts to prevent friction, which is the main cause of heat inside an engine. Use of substandard engine oil, old oil that has lost its viscosity, or an engine oil that is low in level can also result in engine heat up.
How to prevent engine overheating?
The best way to avoid engine and vehicle trouble due to overheating is to prevent an engine from becoming overheated in the first place. Here is what you should do:
- Ensure that coolant levels are maintained and there are no leaks that would cause coolant to leak out.
- Dirty or inadequate engine oil cannot dissipate heat. Check the oil level and viscosity. Change the oil before a long trip or if it looks past its prime.
- Confirm radiator hoses are in good working order and do not look worn out.
- Have a mechanic check that a radiator fan is working and that there is adequate air flow through the radiator.
- Be aware of engine temperature by periodically watching the gauge on the dashboard while driving.
Lastly, follow these steps if your car gets overheated.
A computer animation professional with over 23 years of industry experience having served in leading organizations, TV channels & production facilities in Pakistan. An avid car enthusiast and petrolhead with an affection to deliver quality content to help shape opinions. Formerly written for PakWheels as well as major publications including Dawn. Founder of CarSpiritPK.com