I have a 1997 hijet van 993cc which has recently begun overheating. Started with occasional boiling sound after engine stop, and getting hot while stuck in traffic. I have had a slight noise from the front of the engine for some time which I assumed meant either alternator bearing going or water pump. Took it for mot the other day and they said they couldn't complete test as it boiled over. Swapped fan switch (as fan had been temperamental occasionally) in rad today and still same although fan came on as it should. Re-filled rad with clean water to test, and as engine warmed up began running slowly back into expansion bottle but was frothy(?), no obvious sign of oil in water, or leaks anywhere, and engine seems to run ok, but seemed as though air in system or water boiling although correctly filled with bleed rubber above rad removed.

Methinks water pump probably gone, although would also like to replace engine side cap to be certain that is ok. Rang local dealer who quoted nearly £30 for just that cap! Will check if play at the end of the water pump pulley tomorrow and got friendly mechanic coming to look sunday. Anyone know what might fit as engine side cap that I can get elsewhere, and where to get a water pump if indeed it's that.

I know my local dealer just thinks of a price then trebles it for everything, but £30 for what is essentially a radiator cap (and have only just paid another £30 for the rad fan switch)!

Blown gasket.

Overheating could just be a thermostat stuck closed so the coolant boils.
Possibly a water pump problem but that can be checked by removing the radiator cap and reving the engine ... the water lifts up the radiators neck when the water pump 'drives' the coolant. However you have coolant being expelled into the overflow bottle and this suggests an expensive repair.

Coolant leaking back into the expansion bottle is usually due to a cylinder leaking through a head gasket into the coolant. The pressure leaking from compression of a cylinder forces the coolant from the engine block into the radiator and the excess is pushed into the overflow bottle. Oil may not be present since the leaky head might not be postioned across an oilway. Hopefully it is only a broken head gasket and not a cracked cylinder head. Don't drive knowing it is overheating .. a hot spot could develop and blow a hole in the cylinder head.

Smell the overflow bottle ....... does it stink of petrol or exhaust fumes? A certain sign is bubbles escaping from the overflow bottle .... bubbles smell of petro/exhaust fumes.