Ok, I am really hoping someone can help on this one.

This is regarding 1980 300D.

I am having temperature issues. Usually I'll be driving along and the temp guage reads around 90 degrees which I feel ok about. That's what my last 300D ran at. But randomly, I can not find any kind of pattern here, the guage will jump up to 100 degrees and sometimes even creep beyond that. When I say jump, I don't mean it creeps up there, it literally snaps up there, and will snap back and forth between the two temperatures and . It seems like the slower I'm going, the less it happens but I've not had the car long enough to say for sure.

Does anyone have any idea what might be going on? Is my T-stat snapping open and closed? I hate having an engine run at 100 degrees. That can't be good eh?

Thanks,

read

Hello,
It sounds to me like your gauge is bad if its jumping around randomly. My 83' 300d has a hotter thermo, so it runs at 90 to 105 all the time. I did this so my wvo system gets lots of heat. This is just my opinion, but I think that anything under about 115 is ok. I think the car was designed to run a bit cooler, but the cast head should be able to take a bit more heat. I drive up and down steep grades all the time and I have yet to overheat. Please let me know if anyone disagrees!!
Cheers!
Lukas

If the gauge is jumping that fast, it may be a problem with the gauge only. Is the fuel gauge also jumping around? I fixed my jumpy gauges by adding an extra ground wire from the instrument cluster to ground.

Fuel guage does not work at all.

clean the gauge fuse contacts in the fuse box, replace with copper element fuse. If still happening, then the cluster needs to come out and the electrical plug needs cleaned or secured better or another ground added.

Sounds like a loose ground to me.

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Ok, I'm feeling much better about the whole scenario. If that's all it is, I will take care of it. I bought a new T-stat in anticipation of that being part of the issue, but it can't hurt to have that on hand.

thanks!

That's exactly what my gauge did before I repaired the connection to the sender. When it got hot, the contact would get loose and the gauge jumped around.

But it's also not unheard of that a thermostat will stick, but that would not "jump" around, it would be more like an adjustment.

__________________
'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

http://i16.photobucket.com/albums/b1...oD/bioclip.jpg

wouldnt the 80 be a mechanical guage for oil pressure?

so ground wouldnt affect it.

tom w

__________________
[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.

Yes, but it's the temp gauge thats acting up on his car. On my 240D the temp and fuel gauge would jump around in perfect unison with a bad ground.