The past few days I've noticed that my temp gague is running slightly above it's usual position. Yesterday I was looking at it (after driving around) and it was jumping up and down. Anybody know what could cause this?

Merry Christmas,,

Hugh Sr.

1984 190d (W201) 133.232

The jumping might be related to a bad (engine) ground, at least that's what i'd check first.

__________________
General George - 1967 Land Rover 2a SWB 1983 OM617 Turbo

Top the coolant level, and see it that helps.

__________________
Rebe

Does jumping up and down mean the needle fluctuates with no change in load or even at idle, or does it seem particularly sensitive to engine load and airflow through the radiator?

Sixto
MB-less

If the fluctuating is seemingly random, this is what happened to me when the temperature sending unit was failing. It would read high for a while, then bounce back down to normal---sometimes just bounce around within a range.

A new sending unit cured the problem. But definitely check the wiring, connector at the head, and engine ground, as was mentioned, before suspecting the sending unit.

__________________
1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"

In agree to check the engine to body ground. I had that problem, would spike up high, and drop back and jump up again. turn off the engine, restart and back to normal.

I swapped in a new temp sender, even changed the gauge, still the problem.

Finally removed and cleaned ground strap and things were back to normal.

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

I have the same exact issue. Seems when my car gets up above 80 degrees or so it will randomly jump up to 100 and back down. It is very random. I have checked the battery ground and also changed the sending unit. Changing the sending unit made my car run a little cooler but the random fluctuation is still there. And have only seen it do this when the temp is reading above 80.

82 300D

__________________
1982 300D

Where are the ground straps located?

Hugh Sr.

1984190d (W201) 133,232

Ground strap is located beneath the car, connects the engine and body together. Most models it is located on the left side, below where the driver's feet would be.

Just to be clear, the engine temperature cannot change instantaneously due to the thermal mass of the engine. 10 to 20 degree swings over a few seconds are an electrical problem with the gauge system. Now if the temperature swings occur over a minute or so then you have a cooling problem.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech