As your temperature gauge rises higher than normal, going closer to the red zone, you are given the first indicator that your engine is overheating. The second indication is the warning light your vehicle has to tell you the car is running hot. This light is typically found on the dashboard, and you may see steam rising from the bonnet. When any of these signs appear you need to stop driving the vehicle. To continue driving is asking for brutal and costly injury to the engine.
At any time that you see a warning light that your engine is running hot you should pull of the road and turn the car off. You should not continue to a service station or mechanics garage. The injury to your car will be a lot worse, especially to the cylinder head. The cylinder head can warp or crack under increased temperatures, and is very costly to swap out.
Once safely parked on the side of the road, switch on your hazard lights to warn any following drivers of your problem. Providing that there is no fire present you can open the bonnet, to give the engine a chance to cool down, however do not be tempted to touch any of the engine parts at this point, as it is very likely that you will be burnt.
Be prepared that it may take quite some time for the engine to cool down sufficiently so be ready for a long wait. If your vehicle has overheated when it is dark, switch on your sidelight bulbs to improve the visibility of your vehicle to other road users and consider turning on your headlight bulbs to help you see what your are doing.
Once the engine has cooled down you will probably need to top up the coolant level. In an emergency it is fine to use ordinary water but make sure it is not too cold or it could crack the plastic water reservoir. If you need to add a lot of water to your coolant it will significantly dilute the concentration of the antifreeze within it, and this will eventually need to be remedied by a qualified mechanic to prevent the coolant freezing during the winter.
Even if the engine has cooled down the coolant may still be hot and undoing the coolant filler cap can release scolding hot steam onto your hand. Therefore wait until the radiator is cool enough to touch before opening the coolant filler cap and cover your hand with a rag for added protection.
Reaching out at arms length to fill the container will help stop you from being hit with hot coolant. You will want to stop and check the levels of the reservoir to ensure you are not over filling it. There is a maximum and minimum line on the container. You will need to check that the temperature gauge is back to normal levels before driving again.
Remember that whilst your car is safe to drive again, there is an underlying problem that caused the overheating, so avoid a long journey and take it to a suitable garage to be checked out as soon as possible. However, if the engine overheats again, shortly after you have set off, you need to pull over and call a roadside recovery service as you have a serious problem that will require the services of a garage to fix it.
When packing for a motoring holiday it is also a good idea to pack some spare Car Bulbs as well, just in case a bulb does blow during the holiday, as finding a replacement abroad can prove difficult. It is also a good idea to install long life Headlight Bulbs before setting off, as this will reduce the possibility of a bulb failure even further.
