I have tried 2 brand new brand name 80 degree C rated thermostats in my '83 300DT. The car consistently runs at 95 degrees C. Even after I put in a new temperature sending unit. The original thermostat that the car came with when I bought it a few months back, makes the car run at 80-85 degrees. I replaced it only because it evidently was sticking open a bit as it took a long time for the car to warm up. Now I put it back in the car. It runs steady at 80 degrees and never goes beyond 85. The only penalty is that the car takes much longer to warm up.
I replaced the thermostat in my 300SD about three years ago. The car steadily runs at 85 degrees C and warms up pretty quick.
What I have concluded is that at some point all these new 80 degree rated thermostats have been calibrated to actually open at about 90 degrees C. For what reason I have no idea - maybe hotter running diesel has less harmful emissions? At any rate, I really believe that there is nothing wrong with my car or its cooling system, except I cannot find a new 80 degree thermostat!
because they evidently do not make them anymore, despite stamping 80 degrees on them.
I hear similar complaints from other people. In fact, there is a long article on the same subject on dieselgiant.com Has anybody put one of these new thermostats in water to see at what temperature it opens? If anybody knows of any new thermostat that actually opens at 80 degrees that fits these cars, let me know. I am getting really tired of this. Now I have a brand new radiator sitting in a box, which will evidently do nothing, because it will run again at 95 degrees with one of these stupid new thermostats!
