Hi all,
I decided to replace the air box thermostat on my 92 wagon, not knowing if it ever had been replaced and as preventative maintenance before winter. A few weeks ago, I had replaced the flexible metal pipe directing warm air to the air box from the right engine side (it was falling apart and full of gaping holes so even if the thermostat worked, it may not have done the job.

Anyway, got the airbox out, and figured out how to pop out the thermostat. The flap was closed at room/garage temperature (about 15C). I noticed that the thermostat in there had a short stem coming out of it, maybe 5mm. Whereas the brand new thermostat I ordered for my car has a stem about 1.7cm at room temperature. That would leave the flap wide open at engine cold and ambient temperature 15C. I tested the new thermostat by immersing the metal base in very warm water (80C?) and came out slightly, to about 2.1cm. I tested it then by putting it in the freezer for a couple of minutes and it retracted to about 1.6cm (from 1.7 at room temperature).

1. Why is the new one so much longer than the original/old one? Was I sent an improper thermostat?

2. Assuming the new one is correct, what do I do to make it close the flap at cold temperature (cut the stem)? Will 5mm travel from frozen to very warm be enough to effect a full travel of the flap in operation?

First time I've taken these suckers apart, so I'm a little baffled and will welcome words of advice. The Bentley manual is not very helpful, and the Haynes is even worse.

Thanks.