The causes and consequences of engine overheating
The most typical causes of engine overheating are:
Engine overheating is quite a frequent summer problem. Let's look at the most common reasons why it may happen.
The first cause is a lack of coolant in the cooling system. In this case you may see stains of water or coolant on the exterior of the engine. If you start moving after a long parking, you may see a puddle of fluid on the ground at your parking place.
The second possible cause of engine overheating is the accumulation of dust and dirt on the radiator fins. This extremely deteriorates air cooling of the radiator, because the layer of contaminants prevents the air and the surface of the fins from direct contact, which reduces the heat exchange between the air and the radiator.
Another cause of engine overheating is a cooling fan failure. If your fan is driven mechanically from the pulley of the crankshaft, the problem may well be in low belt tension. If the fan is electrically powered the problem may be in a malfunction of the temperature sensor.
The fourth possible cause is scale deposition on the inner surface of the cooling system. The deposition may appear if you use too hard water (with high mineral or salt content). The operation of the thermostat gradually deteriorates and its movable part loses its resilience. In the end the thermostat loses its ability to react to the temperature of the fluid coming out of the engine. The result is that the fluid runs only through one of the loops, which leads to bad heating or overheating of the engine.
Deposits may also accumulate in the combustion chamber. This happens when excessive oil constantly comes to the engine cylinders. In this case, even despite great oil consumption, the lubricating ability of the oil falls down (this happens when a car has long been in use and has a high mileage). Just to note, this situation is extremely dangerous to gasoline engines.
The next cause of overheating may be long operation of the engine while towing or idling. All of these are abnormal modes for engine operation, affecting the engine.
Overheating may occur if a gasoline engine runs with abnormal combustion. Depending on how long you run a knocking engine and the intensity of detonation, its components may get damaged (classic issues are: burned-through pistons or block gasket, broken piston rings, worn crankshaft bearings). The other result is engine overheating. If this is the case, you can see typical signs of detonation – strong exhaust fumes, as well as distinguishable metallic thud.
Some more causes
Another frequent cause of engine overheating is misoperation of the ignition or the injection systems. If combustion is late the temperature of the exhausts will raise extremely high, because the fuel in the cylinders stops burning right before the opening of the exhaust valve or even later so the overheating is unavoidable.
The exhaust valve itself can burn-through as well. A crack in the valve will let the burning gas through during the process of combustion. This will cause the overheating of the exhausts and the engine itself.
Possible consequences of engine overheating
As a rule, when engine overheating occurs, the first thing to happen is cylinder head deformation. This connects the lubrication system and the cooling system to each other and the coolant starts coming to the lubrication system (the coolant level starts falling down rapidly). Oil, accordingly, goes to the cooling system. Another suffering component is valve stem seals. They can’t handle their function properly anymore and the engine starts to consume a very large amount of oil.
The following typical consequence of engine overheating is over-expansion of the piston rings. At a temperature much higher than they’re designed to operate at, they expand and damage cylinder walls, which expand much more slowly. That’s why engine overheating often causes the deformation of the cylinder walls.
Finally, engine overheating causes partial melting of the crankshaft bearings material and their tight bonding to the crankshaft. This happens because of liquefaction of the oil (in liquid form it loses its lubricating ability). The eventual sad consequence of engine overheating may come as a locked up crankshaft.