I have a 1984 300d, just noticed the oil pressure gauge is pegged at 3. Even after changing the oil it has made no difference. This has just happened over the last day, always ran right where it was suppose to. Any ideas what could be causing this? I searched high and low but only came up with threads that discuss low oil pressure.
Thanx Jimmy

3 is the normal pressure for these vehicles... I have no idea why MB decided to install an inadequate gauge... I would love one that goes up to 9 or so, just to know where the oil pressure really is...
it should be at 3 at idle when cold, then after it warms up, as low as 1.2 is fine.
if it still stays pegged at 3 after a long drive, you may have too thick oil in there, should not be above W40 in these cars..

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1987 190D 2.5Turbo
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1987 300TD
1987 300TD
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3+ is good...

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'97 Jeep ZJ Laredo
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Can be a shot oil pressure relief valve...
Pressure relief valve on oil pump engine 616,617 8.0 or 7.0 (8.0 or 7.0 atu)
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=123132&M=617%2E912&GA=722%2E118405&GM=716%2E005++++++++++++++717%2E400&CT=M&cat=143&SID=18&SGR=015&SGN=01
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Engine/615/18-005.pdf
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Engine/615/18-215.pdf
Good luck,may want to check with oil pressure manometer first....

Can you explain what you mean by 'always used to be right where it was supposed to'? Pegged is where it is supposed to be over about 1500 rpm's. If your gauge was not pegged under those conditions in the past, it seems that it had some problem in the past and it has now been resolved.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

At idle it was always just under 2, now at idle it is pegged at 3. In the past when I increased the rpm's it always jumped right up to 3. Have been using 15w40 and I have not changed anything. Just don't want to get stuck anywhere.
Thanx Jimmy

At a hot idle just under two is typical on an engine that has any kind of miles on it. I have seen a freshly rebuilt engine that maintained just under 3 at a hot idle but a year later it was back to just at tad over 2. If your engine is in good shape at a cold idle it should be 3 but once it warms up expect it to drop to somewhere around 2.

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green 85 300SD 200K miles "Das Schlepper Frog" With a OM603 TBO360 turbo ( To be intercooled someday )( Kalifornistani emissons )
white 79 300SD 200K'ish miles "Farfegnugen" (RIP - cracked crank)
desert storm primer 63 T-bird "The Undead" (long term hibernation)

http://ecomodder.com/forum/fe-graphs/sig692a.png

possibly a faulty gauge? I would suspect it more in a w126, as its electric

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1981 300SD 512k OM603

Since I got it six months ago, my 240D has always run at 3 - idle or revving.
Oil change didn't change a thing. I am running 5-40 (I think), but I live in a hot climate (We had one or two nights below freezing this winter).
Had someone say they thought I had a faulty guage or sender, but it sits at zero with the key on but engine off, and gently rises to 3 within a few seconds of starting it up (probably less than 2 seconds, actually). It seems to be no problem for me - my car runs great! Starts before the starter even gets around once, no smoke, smooth idle, etc...

The 300TD does idle at or a hair below 2, then up to 3 as soon as the accelerator is pushed.

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT