Nearly all vehicles manufactured these days come with internal combustion engines, which are notorious for being very inefficient because they produce a large amount of heat in order to get going. The heat is produced within the engine by friction and combustion, and internal combustion chamber temperatures can reach as high as 1093 degrees Celsius. Without a proper cooling system in these extreme conditions, overheating occurs and causes a number of problems.
Hoses Under Pressure
If you are driving a car that is overheating but still has coolant, as in the case of having a faulty thermostat, the high temperatures can cause the antifreeze to boil, expand, and cause intense pressure within the radiator hoses. This can potentially result in hoses suddenly bursting or spraying hot coolant from a weak or broken seal.
Warped Cylinder Heads
Many vehicles are equipped with aluminium cylinder heads, and aluminium is not a material that can withstand a lot of heat without warping or melting. If you let your car overheat and keep driving, the cylinder heads will eventually begin to warp. When this happens, it can lead to a blown head gasket, which would require a lengthy and expensive repair. It also conflicts with the combustion process as the heads do not perform as well when they are warped. The signs of having warped cylinder heads include decreased engine power, misfiring, oil leaks or excessive oil burning.
Blown Head Gasket
The worst-case scenario when you drive your car too long while it's overheating is a blown head gasket, because not only is it devastating to your vehicle, it's also one of the most costly repair jobs you'll ever have. When the head gasket blows, it allows engine coolant to leak and mix with the engine oil. Needless to say, vehicles are not designed to function properly with antifreeze in the oil. The symptoms of a blown head gasket include milky engine oil, thick white smoke coming from the exhaust, and severely decreased engine performance.
Melted Engine Components
A lot of other components surround the engine compartment that are subject to damage from intense heat. Welds, seals, sensors, belts, electrical wiring, and parts like the exhaust manifold, steering column and fuel pump are all at risk when you drive your car while it's overheating.
Damage to Exhaust System
Despite the fact that the car is overheating, an ample amount of hot gases still are travelling and exiting through the exhaust system. This can cause significant damage to the exhaust manifold and catalytic converter if the temperatures are high enough for a long period of time.