I was having trouble with my 84 280e getting hot. It never boiled over but the temp would go up to near 100 and wouldn't cool off without shutting the car off and letting it sit for a good while.

This was after having the clutch fan fail a while back. I replaced the clutch fan and this overheating pattern appeared. Before the failure of the clutch fan all had been fine.

So I bought a new stat but it was a cheapy thing, all that I could find locally on short notice. So I decided to test them both with the pan of water boiling method. I found that the old sat would begin to open at a fairly low temp and would finally open fully. The new stat would open all at once at or near a given temp. I did not have a thermometer to be able to tell exactly what temps all this was happening.

I was dubious but decided to put in the new cheap stat. It worked perfectly.

So I guess bottom line is that all stats do not fail the same way. And if you have a cooling component failure which allows the temp to go up pretty high, it may cause a failure of the tstat.

Also a stat that opens and closes in a pan of boiling water does not necessarily work well enough to cool your engine correctly.

And although they look very similar and have the same outside diameter, the 280 stat is not the same as a diesel stat. The disc on the bottom of the 280e stat is larger, and the 280 stat has a bleed device which allows a bit of water to flow through outside the normal passage. I cannot imagine what the function of that is since the stat is a bypass stat and always is flowing water one way or the other.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.