Please don't let it be the Head Gasket

jeremy · Post by **jeremy** » 17 Dec 2006, 21:50

The normal failure of a water pump is for its glands to fail as anyone who has ever owned a car made by Rover or BMC or any of its limbs will be able to tell you. If the glands go the thing continues to pump but just leaks.

Its a very simple device - basically a pulley, a seal, a bearing and an impeller fitted on a plate and in turn bolted into the water jacket. As its simple it is reliable, and normally failure will be leakage or bearing failure. Both will not really impair its pumping ability.

Just occasionally (and you're more likely to be run over by a bus twice on the same day) the impeller drops off, in which case it will stop pumping altogether. It is also possible for the impeller to corrode badly causing a drop in output but this is unlikely too.

If the impeller were to drop off the forced water circulation would cease. There would be a little thermosyphon circulation but this would be confined to the engine itself. (based on hot water rising)

If the water boiled it would produce steam BUT when it cooled the steam would condense back to water. The process of boiling would NOT introduce any gas into the system. Any gas MUST come from elsewhere - like through the head gasket.

Post by **Peter.N.** » 17 Dec 2006, 22:26

The head gasket will only cause all your symptoms if it is leaking so badly that it is blowing a lot of the water out soon after you start it. When you have filled the system with water and started the engine, how long does it take for the pressure to build up? can you see any water being ejected? do the radiator hoses go hard almost immediatly? If the gasket has failed badly or if the head has cracked, it will normally blow large quantities of water from the header tank when you rev the engine (without the cap on) If you are not immediatly losing a lot of water when you rev the engine, I am baffled!

tomsheppard · Post by **tomsheppard** » 18 Dec 2006, 21:04

Standard test for head gsket failure will be described in a minute.
Firstly though we need to assess the lack of water in the heater matrix. If the tap doesn't open then the water don't go in and you get an air lock, no matter what the bleed screws are telling you. You have to be sure that the heater is full by warming the car gently until the stat opens(Top hose suddenly becomes hot, likewise radiator). Check radiator to see if it is warm all over. If not then blocked rad or air lock in rad and in all probability game over with HG.
The test goes like this. With the engine fully topped up to its maximum level and stone cold, start the engine, run it at idle for 45 seconds and switch off. Remove cap. Fountain? HG gone. No fountain, 99% certainty that HG is ok.

jeremy · Post by **jeremy** » 18 Dec 2006, 21:24

Tom

The heater on the ZX is an air blender and has no water valve. From what others say it would seem the Xantia is the same.

Mariner · Post by **Mariner** » 18 Dec 2006, 21:42

Tom,

your head gasket test is very straightforward thanks I will try tomorrow. I think Richard you mentioned this earlier also but I had to read quickly as I was at work so missed your point.

I will post the results tomorrow also.

What i am also going to do is check for water pump failure. I have been told that if I remove the pipe from the head next to the thermostat housing and then rev the engine, if the pumps working it should pump out water. Is this about right?

By the way thanks to everyone on this thread for their input.

Mariner · Post by **Mariner** » 19 Dec 2006, 11:20

Well thanks to everyone on this thread I know the cause and outcome of failure.

The water pump isn't working even when the engine is revved.

The head gasket has definitely gone (water erupts out of the radiator cap after only ten seconds of running)

I will therefore be getting rid and have a few almost new parts on it to sell, I'll put these on the for sal forum.

Thanks again for everybody's input.