Club 80-90 Forums

Hi,first time i've posted so here goes.
I bought my van(1.9 dg waterboxer 1986)backend of last year and on the way home disaster struck,the expansion tank burst(too much pressure or old age,who knows?)Anyway got home and bought a new one from justkampers.Fitted it and all seemed well for a while,then a coolant leak started from the passenger side water jacket/cylinder head coolant gasket.Bit the bullet and whipped the head off and replaced gaskets etc.
Now to the problem,with the expansion tank full to the top when cold and once the engine gets warm and up to pressure it seems rather than open the valve in the cap to allow water into the top up tank it leaks from the seal around the cap instead.Surely if the pressure was getting too much the pressure should be relieved to the top up tank?
When i bought the new tank i noticed before fitting it,it had a max mark about half way up the tank,should the tank just be filled to this mark or should the tank be full to the top?If i have the level half way up the tank there are no leaks but i think gradually water will be drawn from the top up tank until the expansion tank is full again and then the leak will start again.I'm thinking maybe the pressure cap is faulty?I have only the original one from the tank that burst and the new one that came with the new tank.I'm finding it difficult to believe both are faulty.
If anyone has had a similar problem i would be glad to hear how you solved it.
Thanks in advance for any help/advice.
member no 2912

Expansion tank should run between max and min marks.

Non-VW pressure caps are notorious for causing problems. Pay the extra nd buy a genuine VW cap from your main dealer, or Baxter sells `em and will post you one, £11.00 I believe?

I think people by the VW caps as there have been issues with GSF ones in the past maybe JK source from the same supplier? I dont think the expansion tank has a max mark as it should be full, or else it won't work as there won't be a vacuum to suck back the liquid from the top up bottle, maybe someone with a little more knowledge can help more, is it on the wiki, top of page>/?

Am I getting mixed up again? When I say expansion tank I mean the one that you DONT top up through the little service hatch , the one with the blue cap with the hose on the cap, this should be full????

The tank should be full, the cap allows the expansion to the "top up" tank
You must ensure the rad is bled correctly too..

You should fit a new cap...
its possible the tank is a "second" and the thread and seat area are not in exact alignment...

Westy.Club.Joker wrote:Expansion tank should run between max and min marks.

Just to remove any confusion, the expansion tank is the one under the engine lid with the pressure cap, the top up tank is the one you fill from behind the number plate flap,

the expansion tank should be full to brim, the top up tank full to fill hole when engine cold , it will sort its own level out, the is no min max on expansion tank if its the correct one.

Thanks for all the replies,didn't realise non genuine caps caused so many problems.Maybe the original cap caused the original tank to burst and maybe the replacement cap doesn't work properly(lot of maybes in there).Shall try a new vw one and hope for the best.

I do not have a dg engine but a 1.6td diesel.But i no about the g.s.f cap problem .I replaced a new g.s.f with an other but still the tank spewed out coolent .When a VW replacement cap was obtained the tank did not leak and kept its preasure.

Hi finally got a new vw cap and fitted it,had to replace the hose with a longer one as the pipe ended up facing the wrong way.The good news is that when the engine gets up to temp ie. the fan cuts in there are now no leaks from the cap.Still no release of pressure to the expansion tank but this could be due to the pressure not being high enough,maybe when the weather gets a bit warmer and the cooling system has to work a bit harder this will change.Thanks again for all your replies.