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  #1  
Old 02-28-2007, 10:12 AM
Mookie32
 
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Oil Pressure guage stays up at 3

My oil pressure gauge bottoms out when the enging is off but then shoots up to 3 when the engine is on. This is despite a massive oil leak and the dip stick telling me that I'm down 3 quarts.

The leak is coming from the oil return tube coming off the turbo and I can't get a clear picture of whether the tube is busted or the grommet is broken.

Any ideas?



1985 300SD Turbo.

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  #2  
Old 02-28-2007, 10:30 AM
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When the engine is cold, that is a normal oil pressure.

The oil leak from the turbo oil return tube would likely be from the O-rings hardening at the joint where the 2 sections mate. Also, the grommet at the bottom gets pretty hard and fails to seal. From what I've read this is a pretty common oil leak area on this engine but really simple, and inexpensive, to repair.
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  #3  
Old 02-28-2007, 10:31 AM
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If the gauge is staying pegged at 3 bar even when at operating temp, then its most likely your electric pressure sender going out. The W126's have an electrice sender at the oil filter housing that is known to fail, whereas the W123's have a straight oil feed line to the cluster.
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1984 300D 225K
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  #4  
Old 02-28-2007, 10:32 AM
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oil return tube is not under pressure, it just gravity drains to the pan, so it leaking will not affect your oil pressure. also being down 3 quarts will not affect your pressure, that is, unless you are stopping or starting or turning and starve the oil pump of oil. the 8 quart system most of us have really gives us a pretty safe margin of leakage...
how are you reading the dipstick to show 3 quarts down?
John
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"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
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1987 190D 2.5Turbo
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  #5  
Old 02-28-2007, 10:34 AM
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Oil pressure

That is the oil pressure not the oil level and is measured from the oil pump
so you can still be low and have good oil pressure witch is a good thing to have
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  #6  
Old 02-28-2007, 11:08 AM
pjc pjc is offline
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The oil pressure sender is a $50+ part. Anyone know of a way to test it to be sure it's bad?
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  #7  
Old 02-28-2007, 12:25 PM
Mookie32
 
Join Date: Aug 2006
Posts: 35
Quote:
Originally Posted by vstech View Post
oil return tube is not under pressure, it just gravity drains to the pan, so it leaking will not affect your oil pressure. also being down 3 quarts will not affect your pressure, that is, unless you are stopping or starting or turning and starve the oil pump of oil. the 8 quart system most of us have really gives us a pretty safe margin of leakage...
how are you reading the dipstick to show 3 quarts down?
John

I eyeballed the dipstick, made an estimate, put in 3 qrts. and the dipstick had oil right at the full line. Not scientific, but I think it works.
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  #8  
Old 02-28-2007, 12:30 PM
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Ahh, that makes sense.
I was wondering if I was missing some mark on mine.
John
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #9  
Old 02-28-2007, 01:50 PM
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Once the wire for my oil pressure sensor came off and the gauge went to 3 bar, since i had had this car for two years I knew what the oil pressure should have been at that temp, so I checked out the oil pressure sensor and sure enough the wire was just dangling. So check that first.

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