thal

Hi All,

Started noticing my themperature gauge rises to the highest white line ( the one before the red overheat line), then it appears the thermostat opens and the gauge drops back to the first intermediate white line. Is this symptomatic of a sticking thermostat? I don't seem to recall this behavior previously. Although I confess I have been working on the car for the lastm couple of years and forgot past behavior.

Thanks in advance.

mark kibort

they rarely stick . what you probably have is air in the system or a leaky rear seal on the t-stat, if you have a newer car, OR just not enough water in the system, (should be over the seam of the overflow tank)

quick check: when it goes red initially, go to the radiator and feel the heat distribution. it will be cold near the bottom driver side most likely. yes, it could be sticking, but again, that rarely happens.

thal

thanks mark, i'll check tonight.

Tails

To verify the function of the thermostat, remove it and put it in a pot with a thermometer and heat the water up and record the temperatures of opening, when it is fully opened and and the distance the valve has travelled.

The WSM has a full description of the operation and testing of the thermostat.

Tails 1990 928S4 auto

dr bob

There is some hysteresis in the thermostat. The behavior you observed is very normal, and it's quite likely been doing this before and you just noticed. Of course, now your driving will suffer as a consequence. You'll be staring at the temp gauge, watching for it to open initially and let a charge of cold water run through the motor. Use your bad eye on the gauge, and save your good eye for the driving chores.

thal

roge-o on that one Bob. no, i'm ready for both eyes on the road.

thanks.