Originally Posted by JCL

Overheating can also be caused by the engine working too hard (such as pulling too big a load) in too high an ambient temperature, ie producing more waste heat than the cooling system can get rid of. In that case, turning the engine off is the wrong thing to do, as you put the engine into a hot soak, and the block temperature will climb once you cut the coolant flow. The right thing to do in that case is to remove the load and let the engine cool.

Given that this is a BMW site, readers should be aware of the need to bleed the cooling system. Often you can't just fill it with coolant or water, you have to take the air locks out.

When routinely changing or adding coolant, always use an approved coolant type for your particular vehicle. There are different types of coolant, and you need one compatible with the components in your cooling system.