1985 300D.
I am having an issue with either coolant temp or coolant temp readings and hope someone can help. Our temp gauge started reading low around 40c to 60c. It had always read around 80c before then. I assumed the thermostat.

I replaced it, and am still having the same issue. I tested the old thermostat, and it opens in some hot water no problem, so I have to assume there is another issue. (unless both thermostats are weak?) As I'm fairly certain there is no air bubble, and the aux pump seems to work (heat and defrost work at idle). The coolant temp sensor is my next suspect, unless there are some other options you all may advise. After some research that seems the likeliest culprit though. What say you guys? Anything else that can cause this condition? Thanks!

__________________
1984 Astral Grey 300TDT - The French Fry
1979 Yellow 300SD - The Pomme - SOLD
1985 Light Ivory 300DT - Fritz
1987 Anthracite Grey 300SDL - ?

i'd check sending unit

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

Sinner,

Do you mean the temp sensor mounted in the head? That is the part I'm referring to. How does one check that? Resistance? What should the readings be? At what temps?

Thanks

__________________
1984 Astral Grey 300TDT - The French Fry
1979 Yellow 300SD - The Pomme - SOLD
1985 Light Ivory 300DT - Fritz
1987 Anthracite Grey 300SDL - ?

well they do wear out,it would be a cheap fix,or borrow a infared thermometer

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

Coolant temp sensor installed. Issue resolved. Thanks.

__________________
1984 Astral Grey 300TDT - The French Fry
1979 Yellow 300SD - The Pomme - SOLD
1985 Light Ivory 300DT - Fritz
1987 Anthracite Grey 300SDL - ?

For future reference, Diesel Discussion is the more correct forum to post this in -- it's right below Tech Help on the list.

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."