On my 1982 300D I recently replaced the Thermostat (On Saturday the 15th) because the old one was stuck open. I knew this because on my trip out to Ft Worth during the day time the temp would sit at 80C and fall to 60C when the sun went down, also the heater wasn't very warm. I was driving at a very nice clip so having the temp under 80C was kinda a dead give away.

Anyways, when I was in the garage replacing the thermostat I drained the radiator of it's fluid and proceded to remove the old thermostat and put the new one in. I didn't have a single problem and I put the T-stat in the right direction (not sure if it could go in backwards). I then put it all back together and filled the resevoir back up with new Antifreeze while letting the engine idle with the heater on. It took about 5-10 minutes for it to get to 80C when the temp dropped back down to about 60 (cause of the cold coolant getting into the Engine). After it got back up to 80 I decided to take it for a little spin to see how it did with air flowing through the radiator. After 5 minutes the temp jumped to 100. Since I never saw this sort of behavior from my temp gauge I desided that I'd better stop my test and let some air work it's way out of the system.

Now we jump to today (the 19th). The temp is doing a lot better then on Saturday. Instead of jumping to 100C after a few minutes it works its way slowly to 80 then a little quicker to 85-90 and then hops between 100-95C (with the Heater on the whole time). I don't dare turn the heater off.

I know that this is way to high especially since it's only 65F outside. Could it be that the temp gauge is wrong?
I don't think there's any large amount of air in the system because the water level hasn't been going down the last 2 days when I checked it in the morning (I drive it 20 miles everyday at least, so its safe to assume the bubbles have worked themselves out.) I also know that the themostat is of the 80C variety and it's from the local MB dealer (has the star on it and all).


Any insight would help. It's very disconcerning when the temp is just sitting at ~100C.

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2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/showthread.php?p=852260

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP