> I've own my 87 GL since new and it now has 211,000 miles on it, new engine
> now, never replace the radiator and I was wondering if its time to do so
> because of the slow traffic/hi altitude over heating. The expansion tank
> when it over heats empties into the overflow tank and exposes the sensor

I don't think this would happen is the system is working like it's supposed
to... shouldn't expose the sensor...
It sounds like you have air/gas in the system... either the cooling system
wasn't purged of air properly or you may have combustion gases getting into
the coolant system... I guess it would also be possible for air to enter
they system if you have a leak somewhere high in the coolant system....
would maybe suck air into the system upon cooling down?

and
> the red like begins to blink. If I relive the cap on the expansion tank I
> can get the coolant to suck back the expansion tank.

not sure what you mean by 'relive the cap' but you shouldn't have to do
this... I'd replace the cap on the expansion tank pronto....

Good Luck,

bill

 I had to do this all
> the way home the other day when I went in to hi altitude roads.
> Any help will be appreciated
> Dan
>