>I got a few weeks ago the same problem than yours and I change the cap, but
>I'm not sure the problem is really fixed. Also the level of coolant is
>changing pretty often in the expansion tank. Sometimes it's full, sometimes
>it's half full. Any idea about this? I don't really trust the van right now,
>that's why I don't go very far from home. What a shame!! I should ad it's a
>turbo diesel but I think there is nothing to do with the cooling system.
>
>Thanks for any good advice,
>
>Philippe Oudot 
>'89 16" Syncro TD Oettinger
>French Syncro Club

Philippe, you may also have a leak in the cooling system, letting
air in and coolant out. On my diesel Vanagon I've had coolant
leaks in many places over the years: 

1/The "fitting" on the head where the coolant bypass hose is attached. 

2/The block heater installed in one of the freeze plugs in (underside of)
the engine block.

3/Where the upper radiator hose attaches to the radiator. I have metal
pipes under the bus. Newer models have plastic i believe. Note
that the pipes (at least on my bus) are several pieces, joined by
short pieces of rubber hose. Every such joint is a possible
place for a leak. There is at least one pair of joints under the bus
(just behind the fuel tank), and one pair in the front, near the
radiator.

4/The heater valve on the passenger side under the dash. These valves
seem to be junk. The new VAG replacement I bought leaked worse than the 
old one I replaced!

If you have a leak and air in your cooling system you will see different
levels of coolant in your expansion tank and overflow tank because
the air bubbles expands when the engine is warm and contracts
when cold. This "breathing" combined with a properly functioning
pressure cap will try to refill the cooling system from the overflow
tank.

Martin (Diesel VW Westfalia)
--
Martin Jagersand                 email: jag@cs.rochester.edu
Computer Science Department             jag@cs.chalmers.se
University of Rochester          Fax:   (716) 461-2018
Rochester, NY 14627-0226         WWW: http://www.cs.rochester.edu/u/jag/