I just bought a nice, clean 1987 300D turbo with 108,000 miles. Everything seems to be in great shape but I have noticed the temp runs a bit low. It has a new OEM radiator and I'm wondering if it might have had a thermostat for a gas engine installed by mistake. In highway and city driving the temp never goes above 80 and if it is cold out (about 30-40F) and I'm on the highway the temp drops down to below 60. My older 123 300D runs a consistant 85-90 no matter what and seems diesels should run a bit hotter. Are my temperatures normal for the 6 cylinder or do I need a new thermostat? Thanks.

lrg

__________________
LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

I think you need a new stat.

The OEM sta should start opening at 80 deg C.

Mine stays around 85 deg C once warmed up, on the highway or in the city.

Thanks, that's my guess too. I'll try putting in a new one tomorrow and see what happens.

__________________
LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

I own two of these cars, my sister has one, and a friend has one too. They should never run below 80C, at least in ambient temps down to 30F (doesn't get colder than that where I live.) If you're seeing 60C on the gauge either the t-stat is faulty, or the temperature gauge is incorrect (probably the sender, a $10 part), or a poor electrical connection.

My cars run between 80-90C most of the time, and up to 95-100C in the summer (in blistering 105F ambient temps!), but they NEVER drop under 80C after warmed up.

Tip: Don't use an aftermarket t-stat, get one from the dealer or an OEM one from a Mercedes parts source like FastLane, BenzBin, MegaParts, Wholesale Parts, etc...


Good luck,

__________________
Check out my website photos, documents, and movies!

Thanks Bo and gsxr for the input on this. I discovered the thermostat was broken and not closing all the way. My temp is now a very steady 85+/-. An added bonus is that the engine is now warming up faster and much smoother when up to full temp. I haven't checked yet but my guess is the mileage will be better too. It's amazing such a small change can make such a big difference. Thanks again for the help.

lrg

__________________
LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

lrg:

Did the same thing to my 300D this fall -- as soon as it got cool out, the temp started to sag. Mighty cold in that car with no heat!

You should be in great shape now.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!