Well, I can reproduce the problem and see that after the car runs at
idle and slightly higher rpms for 4-5 minutes the cooling system
appears to pressurize, and along with the flashing red light and gauge
going to the top I can see coolant starting to trickle out from the
under the sensor where it goes into the reservoir.  the temperature is
definitely rising and the reservoir is pressurizing and spilling over
into the overflow tank.

If it was a head gasket wouldn't I see some other symptoms ?  such as
vapor from the tail pipe ?

-john

neil wrote:
> a failed (closed) thermostat?
>
>
>
> On 7/20/07, 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
>>
>
>
> --
> Neil Nicholson. 1981 Air Cooled Westfalia.
>
> http://web.mac.com/tubaneil