[Walt Fricke]

Otto

Nothing bimetalic about the thermostat. It works on wax!

That tiny piece which looks like a nail (round flat head, small shaft under it) is forced out of the wax filled capsule as the wax expands with heat. It seems impossible that wax pushing on such a small diameter rod would generate the needed force, but it does.

I have tested several of these units, some of which worked, and some of which did not. Those which did not didn't budge when tossed into boiling water. But I don't recall whether I tried to push the plunger piece back in, and if so, how hard it was to push.

I have been fortunate in having oil temperature gauges which have temperature markings on them, so I don't know just what 9 and 10 o'clock represent in degrees F or C (but lots of other 911 owners do know these things). The thermostat should open at about 90 degrees C or 180-190 degrees F. So first thing I'd want to do would be to assign temperatures to these gauge readings, lest it isn't as hot as you think and that's why the thermostat isn't opening.

But if the 10 o'clock angle puts the needle up in the upper red zone, I guess it is hot.

The next thing to consider is the condition of the piping and front cooler. If it is blocked (or a line squashed flat), not much hot oil will circulate.

I would agree that a new thermostat (or its innards) should work well for more than two years.

Walt