the operation of the 928 thermostat is different from other cars. The thermostat closes on a cold engine, and opens on a warm engine. Its not a good idea to drive without a thermostat because it will definitely trigger overheating, which is other that you would expect.

Here's some additional info:


From: Wally Plumley [wplumley@avana.net]
Subject: [928] Re: thermostat
At 02:16 PM 7/24/00 +0000, eds928gt@freewwweb.com wrote:

Not exactly. When the engine temp is lower than the temp setting to open the thermostat, it is CLOSED. While it is closed the water in the engine is recirculated. When the temp reaches that needed for opening the thermostat, it OPENS and allows cooled radiator water to circulate through the engine. When the thermostat is fully open, the section that allows water to recirculate in the engine gets closed off.

Caution. Never run a 928 without a thermostat.

This leads to an interesting problem. When the thermostat on most other  cars fails on the road, causing overheating, you can usually just remove the thermostat and continue on your way. Doesn't work on a 928 - so what do you do?
One of the 928 Owners Club members was faced with exactly that problem on  the way to Wichita. Luckily, he had read on the list that he couldn't just remove the thermostat, so he didn't make that mistake. What he did was to take the thermostat out and place an 11 mm socket between the operating disk of the thermostat and the engine housing. When he reinserted  (carefully!) the thermostat, the socket pushed it to the open position -
Problem Solved!!
I think that it was Fred Clark, but I may be wrong about that. Darned clever, in any case.
Subject: [928] Re: thermostat

If you look at the 928 thermostat you will notice an extra plate on the bottom. When the engine is cold, this plate is up and allows water to circulate throughout the block. This reduces hot spots during warm ups. As the valve to the radiator opens, the plate closes the recirculation through  the block. If you run without a thermostat, the water will take the path of least resistance and just circulate in the block with very little going through the radiator.