I have a 1993 300D 2.5L turbo. Just bought it and when I travel 30 miles or so the engine temp only gets to about 65C or so (it never seems to reach the 80 C line). Is this too low? How does one replace a thermostat (any step by step instructions)? Is this a big job? Could it be something else? The outside temps are 40-70 C right now as a reference - not running any A/C.

Sounds low to me. Not sure on the replacement on your car but its generally a DIY job. BTW, when you say you are not running the AC, do you mean you are running it in economy mode? You should really leave the system in full auto year round.

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Bill

Backyard Shadetree Mechanic, 30 years running.

1987 300TD
1988 300E (sold, sniff)
1999 S320
1981 Volkswagen Rabbit Truck (Diesel)
2001 Ford Expedition
1988 Suzuki Samurai
On my list to buy: R129, for me, and a R107 for my wife.

Think I'd check the sender, its grounds and also shoot the lower hose with an IR thermo before replacing unless you have little or no heat.

Assume your daytime temps were intended to be listed in F, rather than C. At 70C you'd def have the AC on...

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)