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Old 03-16-2005, 06:48 PM
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oil pressure problem?What are probable causes.

Description by vendor, car pins needle at three bar cold idle but sags to 0 bar once warmed up at idle. Resumes apparent normal pressure at cruise he states but his normal may be sub standard as he does not state what that pressure is.. He's saying it's the sender but I do not think so. States car has 122k but pretty safe to assume has under 200k I think. Car is too good in general to have much more as seats look like brand new. Spring must be coming as I am getting the urge to go buy another car. Wife will shoot me but whats one more wound. Maybe just the o rings in filter,or relief valve stuck partially open? Perhaps obstruction in tube. Oh yes car is 85 300d. Could of course be something more serious and do not think can get a chance to check it out prior to taking car. Know it could be bearings but thought it would be knocking pretty bad with 0 indicated at idle. Suspect he has already checked sender out as a problem as it does not seem smart to sell a car with this problem if it can be rectified so easily. Keeps the price down for starters. Any ideals?
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Old 03-16-2005, 07:53 PM
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Well Barry, I guess nobody wants to see you get shot by your wife, so I'll pass too!

I think you've covered most of the obvious and are hoping for another possibility overlooked. There may be one, but I wouldn't buy it before I knew for sure!

Hopfully someone here can spare your life, or jeopardize it with an answer!
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Old 03-16-2005, 09:52 PM
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sounds like an oil viscosity problem

When was last oil change-any chance oil is fuel diluted? wrong type/broken down? An oil analysis may be in order, I DEFINITELY wouldn't drive it without an oil and filter change(at least).
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Old 03-16-2005, 10:07 PM
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Originally Posted by barry123400
He's saying it's the sender but I do not think so.
All of the diesel W123's that I have worked on had mechanical oil pressure gauges. Which means that they don't have a traditional electric "sender."
I would suggest connecting a direct-reading pressure gauge at the oil filter housing.

Last edited by tangofox007; 03-16-2005 at 10:34 PM.
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Old 03-16-2005, 10:08 PM
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Good thought bullwinkle, never occured to me in this day and age. But possible. He also states that he has been driving it in present condition for quite awhile in fact ever since he first purchased it. Could already have slight bearing or other damage.
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Old 03-16-2005, 10:35 PM
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a thread similar to this just resurfaced the other day. check and clear the pinholes at the top and bottom of the oil canister cap shaft.

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Old 03-16-2005, 11:05 PM
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Pull the dip stick and see if the oil is like water..
might be worth a change to decent oil (if the oil that is in there is old/too thin)
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Old 03-16-2005, 11:16 PM
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Change the oil, filter and o rings before you buy the car. See if that makes a difference.

Insist on an OE filter and at least a 15w-40 dino oil.
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Old 03-17-2005, 10:22 AM
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FWIW, the minimum acceptable oil pressure at idle is only 0.3 bar. (Per the 617.95 service manual.)
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