It sounds like a head gasket problem. The combustion gas may be leaking through
the stainless steel gasket rings on the top of the cylinders into the cooling
system, which forces coolant out of the expansion tank back into the reservoir
tank. If you see the reservoir tank gaining coolant (higher level) it points
the the gasket problem.

This happened to my westy when it was almost a new car. Try to re-torque the cylinder
head nuts. But before that you need to loosen all exhaust headers. You will also need
to remove the intake system in order to gain access to all head nuts. All head nuts
should be torqued to 50 NM. This will not fix the problem if the heads are warped already.

My recent rebuild of my 1.9 engine had a very slight leak. It was first noticed from the
higher than normal temperature and slight increase of coolant level in the reservoir
tank. After re-torquing the heads the problem was completely eliminated.

David

--- John Goubeaux <john@UCSB.EDU> wrote:

> I have a situation where my 90 vanagon, after running for a few miles
> began to exhibit "cooling system problems":
> The temp needle went to the top and the red light began to flash. I
> drove a little while longer and idled downhill home.
> Coolant was leaking out of the (it looks like top of )  pressurized
> coolant reservoir and as well as being under what looks like higher
> pressure than normal. The car did not appear to be overheating. After I
> stopped the engine I could hear pressure noises (what sounded like fluid
> shifting around as the engine cooled off)
>
> Does this point definitively to a head gasket leak? If not what are the
> other possibilities?  My coolant reservoir  had signs of leakage around
> the top where the sensor fits into it prior to this and this was pointed
> out to me by a mechanic.
>
> Thanks !  -john
>

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