When your engine overheats

When the alarms start screaming and clouds of steam erupt from the engine, the first reaction is often to shut it down completely. This is generally NOT the best option.

If you immediately turn off the engine, all water flow (no matter how inadequate it may be) immediately stops. The areas around the cylinder heads will continue getting hotter with no water movement, and serious damage (a cracked cylinder head) can result.

The best option is to throttle right back to idle and take the engine out of gear, but leave it running. This will allow what water is left to continue to flow around, and at least distribute the heat evenly.

In most cases you’ll find the engine temperature drops below the danger zone within a minute or two. While waiting, open the engine cover and see if you can spot the problem. Beware of burns from steam, and never open any coolant filler cap while the engine’s hot.

Once the engine temperature stabilises (hopefully it is now back to normal operating temperature), you can the safely turn it off and attempt to diagnose the problem. Check the raw water inlet and the pump impeller.

If you are in a safe location, wait half an hour or so until the whole thing is cool enough to remove the cap and top up the coolant (some of this will have steamed off). And then make the decision whether to limp home at slow speed or call for assistance from Coastguard.