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  #1  
Old 05-28-2002, 03:04 PM
Randall Kress
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Fluttering Oil Pressure Gauge

My oil pressure needle has been fluttering all weekend, even in the heat. The pressure is where it should be, just the needle jumps, with no surge in idle or anything. Does anyone have any thoughts on the matter?

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  #2  
Old 05-28-2002, 03:06 PM
turbodiesel
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My 83 300D did that too, but only after a very long drive. Not sure what the fix is, but I hear it is pretty common and nothing to worry about.
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  #3  
Old 06-11-2002, 01:38 AM
PSetzer
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I noticed my '79 240D's oil gauge needle was "jumping" when i would press and release the throttle during driving,and when i shut it down and it cooled i checked the oil level and it needed some oil so i added the correct amount and now the needle is stable.
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  #4  
Old 06-11-2002, 08:42 AM
WmHarlow
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Randall,

I wouldn't worry much. Mine has done this a couple of times, but only if it was more than a quart low and driving on the back-country roads. Check your oil level, I believe you may just be a little low. Also, how long has it been since you changed the oil? Have you changed brands or weight? These may be a shot in the dark, but I always check the obvious before replacing sensors or tearing down the oil pump .

Let us know what you find...
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  #5  
Old 06-11-2002, 10:47 AM
Randall Kress
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The issue comes in extreem heat... The oil level is fine, but the oil does need changing... Well, I will see when I get the car back from the shop.
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  #6  
Old 06-11-2002, 11:43 AM
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The 300DT is equipped with an oil cooler. When the oil temperature is below the set point, there is a by pass to enable the oil to warm quickly. When the oil reaches the set temperature, a valve open and the flow (or a part of the flow) is sent to the oil radiator.
My guess is maybe when the regulation valve open and close, it disturbs the oil pressure and it generates some fluttering effect on the needle.
It's just a hypothesis.
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  #7  
Old 06-11-2002, 12:30 PM
WmHarlow
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Excellent Theory!

If the temp were just right, the valve would not know which way to go. I could see the pressure jumping a few PSI. I wonder if this is what is going on?
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  #8  
Old 06-11-2002, 01:06 PM
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There is a fix for a fluttering or trembling (as M-B calls it) oil gauge needle. Install part no. 123 542 00 74 into the oil pressure line at the gauge with the tip end going in first (see, M-B engine manual pg. 18.4 - 005/8). What this means is that a trembling oil gauge needle is normal and nothing is wrong. My needle would tremble at an idle after a run on the highway with 10W-40 oil (for winter driving, about 2 hours long in S. Tex.). I would switch to 20W-50 for the 11.999999 months of summer we have and the needle would not tremble. I now use 15W-40 Chevron Delo 400 oil and the needle does not tremble.

Good Luck!
Tom
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  #9  
Old 06-11-2002, 03:10 PM
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My old '79 300D's oil gauge did that for years, new oil or old. Eventually the gauge started to leak and I replaced it. The new gauge didn't do it. Then the new gauge started to leak and I replaced that. The next gauge didn't do it either so I don't think that the leaking was the cause. I don't think it's related to the oil necessarily either. You could just have an old gauge that is flaky at the lower pressures. My old car is still on the road and going strong (my friend owns it) so I wouldn't worry too much.

Frank
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  #10  
Old 06-11-2002, 06:04 PM
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What about those of us who have an electronic oil pressure guage and have this 'trembling'?
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  #11  
Old 06-11-2002, 06:53 PM
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ck42:

That's a good question. I looked in my repair CD's for all W123 diesels to 1985, found the info about the change to a wire sending unit for oil pressure (guess too many leaks on the old style pressure line ruining nice clothes), and did not find a reference to the trembling oil gauge needle. Off hand, I would suspect the electrical circuit or gauge (loose connections, failing sensor at the oil filter, bad ground, etc.) - however, I do not know.

Bo (ID loubapache) bought some M-B tech bulletins a while back and he may have one covering trembling oil gauge needles. Send Bo a private message/email asking if he has a tech bulletin for this problem.

Good Luck!
Tom
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  #12  
Old 06-11-2002, 09:03 PM
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oil pressure gauge fluttering

randall, mine did that too - in the heat and after a highway run
say when you come off an exit and right down to idle. I didn't worry about it as with any rpm's it always went back to the top.

But that was a couple of years ago and now it doesn't do it.
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  #13  
Old 06-12-2002, 10:58 AM
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What you describe is completely normal. After a long ride (especially with high temperature) my owner's book mentionned than the oil pressure can drop to 0.3 bar when the engine is at the idle. Of course, when you accelerate a little, the pressure should go back to 3bar.

Personally, I have never seen the needle of the oil gauge below about 1.5 bars.
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  #14  
Old 06-12-2002, 11:30 AM
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Thumbs up

Sorry, thank you to correct me
Personaly, I have never seen a high frequency 'flutter' of the needle at idle.
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240D 1984 252 000 km
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  #15  
Old 06-13-2002, 12:44 AM
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Other goofy gauges

Is this tremble common with the other needles in the cluster? My fuel needle does this when I'm around half a tank, and my temperature needle does it from time to time. Doesn't bother me, but if you know why or a fix I'd liketo know. Also my tach sometimes doesn't come up at start up, and I have to rev it for it to read anything... what's up with this? It doesn't do it consistantly.

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