Peter Krogh wrote:

>  my rising coolant mystery.

Peter, I don't mean to be picky  here, but my understanding of the cooling system
is that the tank with the coolant level sensoer in the top of it is the expansion
tank, and the tank into which the excess coolant flows  is the over flow tank. As
the coolant heats it expands, building pressure, at the preset pressure in the
overflow cap, the little valve in it opens and allows the expanding coolant to
escape in to the overflow tank, which in turn has three little holes in it near
the top rear that allows the coolant to literally flow out on the ground if the
tank fills up.

A little over two years ago I had a really wierd cooling problem. When the engine
began to warm the coolant and the coolant began to expand, the coolant did not
overflow into the overflow tank. Instead, the pressure continued to build as the
coolant got hotter and hotter until the coolant level sensor was literally blown
out of the expansion tank, with coolant going everywhere. So, I relaced the
pressure cap with a new one. In addition, about the same time, I discovered I had
a stuck thermostat which wasn't helping matter. Replacement of the pressure cap,
and the thermostat eliminated the problem.

You might look into pressure cap and thermostat replacement.

John Rodgers
88 GL Driver