When your car overheats, there’s more than just the immediate inconvenience to consider. Being stuck by the side of the road is bad, inconvenient and maybe even dangerous if you’re stuck on a fast road.
But your car’s engine could be on the way to serious damage that could be very expensive to repair. Specifically, an overheating engine is prone to distorting and cracking. Aluminium blocks and heads are most in danger, but even heavy old-style cast-iron power plants are open to damage.
If cracking or distortion does occur, you are looking at stripping down and replacing some of the most expensive mechanical parts in your vehicle.
A blown head gasket
The head gasket makes a seal between the cylinder head and the engine block, and stops the coolant, lubricant and combustion gases mixing. As the engine overheats, any small distortion may put extra pressure on the head gasket, leading to a ‘blow’. At this stage coolant, lubricant and combustion gases mix, leading to a range of problems.
Lubrication problems and piston damage
If the damaged gasket subsequently leaks coolant, the engine will tend to overheat again. But that’s not the whole story. Coolant can find its way into the crankcase or the cylinders, mixing with the oil and reducing its effectiveness as a lubricant. In the longer-term, this increases wear in the cylinders and to the piston rings. Less efficient lubrication can also lead to more overheating, feeding a vicious circle of damage-overheating-damage-overheating.
Back to basics
While engine problems can be both cause and effect of engine overheating, the most common cause is simply ineffective cooling. A faulty thermostat can stop coolant circulating; a leaky hose can let coolant escape; and so can a corroded or damaged radiator.
Other sources of overheating are problems with the radiator fan and its thermostat, which may cause the fan to switch on too late or not at all. A failing fan will cause the engine to operate at a higher than optimal temperature, again potentially leading to other damage.
Maintenance is key
Although the consequences of overheating are complex and may well require the services of a qualified technician, it’s generally easy to make sure things don’t get out of hand. Regular simple checks and being aware of what’s happening with your vehicle should be sufficient. Make sure you’ve checked your coolant levels, fan, fan belt, radiator and hoses. A little maintenance can save lots of bother and expense.