I had this problem and it turned out to be a hairline crack in the
reservour bottle near the coolant level sensor.
Replacing the resevour and putting in a new sensor for goo measure cured
the problem.

Todd
'88 Westy

Thomas Brobst wrote:

> If it helps I've had a similar problem for many years on my 84 GL.
> Everything is running just fine and, all of a sudden, I have a
> flashing red
> light on the temp gauge. I comes and goes. When it happens  I just check
> the mirrors for white clouds of coolant vapor behind the van. There's
> never
> anything. It's an electrical thing in my case. My diagnosis says it's in
> the wiring not the gauge pack or the sensor. So I just check the coolant
> level occasionaly live with it. But then, I'm lazy.
>
> Tom Brobst
>