This isn't the worlds greatest problem, but my Add Coolant light (and it's horn) comes on once in a while on the 85GSL. Rad is topped up, and I even topped up the o'flow tank. Car doesn't overheat. Maybe it's just a bad sensor, but maybe it's trying to warn me of something else in the cooling system. Hmmm.

B

 

your rad. cap could be leaking, check it for cracks in the rubber seal. also check the water pump , it might be leaking too

 

Same problem. Went away for several months, now it's back. Car always runs cool and cooling system hasn't lost a drop. I pulled the sensor once and the coolant was right up to the top of the sensor hole.
I may just replace the sensor -- they're pretty cheap.

 

I had the same thing happen to me. The wire on the sensor had a crack in it. I just replaced the sensor. I think it was about $20 with shipping.

 

I had the same problem for a while. Mine was the connection between the two wires. I cleaned it up and it now works good.

 

I had that happen to me too, It turned out to be the rad cap(it was leaking).

I bought a new one, and it went away immediately.