Let's start with some basics. Cooling system should have pressure
    all the time while running. You can test this by squeesing a
    rad. hose.

    Sound to me that you have a bad Rad. Cap. They get clogged
    easy. It should maintain pressure on the system when hot.

                     Eric

On Fri, 12 Sep 1997, Brendan Irwin wrote:

> List,
>
>         I have recently gotten an '87 Westy and have been gleaning lots of
> great info from you all.
>
>         Now, I have a question. This van shows lower temps on hotter days and
> hotter conditions such as in town. When out on the freeway, the temp
> goes above the led, when I would think it should go down.
>
>         If I pull over after a run on the freeway, with the higher temp
> reading, the overflow tank overflows. However, the hoses to and from the
> radiator are not hot at all, and the fan is not going.
>
>         In town, on hot days, the rad is nice and warm, the fan operates
> occassionally, and the temp is about in the middle of the led.
>
>         This leads me to believe that the air cooling of the engine while
> cruising on the freeway leads to a water temp insufficient to keep the
> stock 87C thermostat open. When stopped suddenly, the thermostat cannot
> react fast enough to bring the radiator online before the boil-over
> occurs.
>
>         My question is this: Has anyone explored this problem before? Has
> anyone put the 80C thermo from the '79 Audi 5000 in? (I did this
> morning, but have yet to test it)
>
>         Any suggestions?
>
> Thanks
> Brendan
>