Hello guys, I am at a loss here and I would appreciate some ideas.
I recently bought a w123 200D that was really cheap for prices here in Spain, no rust, perfectly preserved, always slept in a garage etc...

The issue is the car shows 0.3-0.5 oil pressure at iddle, which is above the 0.3 minimum requirement in the OM615 manual, but not normal in any way.
The thing is I brought the car using the highway and the car never got hotter than 90Cº and as soon as I pass 2.000RPM the oil pressure goes up to 3 and stays there as long as I don't go back to iddle.

What could be causing this? I thought about the bearings or a head gasket issue but since the engine is not overheating, I have no smoke, when RPM go up I get to 3 oil pressure and the engine starts and works fine I am wondering where this is coming from.

I recorded two videos to show you the issue in detail:
1- https://www.youtube.com/shorts/PRLVvnOqDwE
2- https://www.youtube.com/watch?v=c7KMB8EjbEU

A partly stuck open oil pressure relief valve in oil pump could do that.
Did you buy the car this way?

Us single viscosity 30wt oil and see if the oil pressure goes up.

Generically trouble shooting this on any vehicle you would hook up another more accurate pressure gauge to see what is really going on.

Not sure where you can get a fitting to do that that.

Also when I removed the oil line that goes to the gauge from the oil filter end of it the tubing and inner fitting were supposed to remain stationary while the threaded part unscrewed. But there was so much rust and crud they were stuck together. I had to cut the plastic tubing to remove it.

See post 33. The large fitting is the one that screws in at the rear base of the oil filter housing and the smaller one screws into the back of the gauge.

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84 300D, 82 Volvo 244Gl Diesel

I had forgotten about it. But in the past, I had pulled the central steel tube out of the oil filter cap and drilled and tapped the center of it for a fitting. The centra steel tube is just pressed inside of the aluminum cap.

See post 13
http://www.peachparts.com/shopforum/diesel-discussion/353335-where-sense-oil-pressure-617-a.html

That also reminds me of something I should have thought of first. The bottom of that central steel tube has 2 O-rings. When those O-rings get hard or crack the idle oil pressure can be low.

Post 26 has a picture of the 2 O-rings on the tube end.
http://www.peachparts.com/shopforum/diesel-discussion/308259-om617-o-rings-oil-filter-shaft-2.html

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84 300D, 82 Volvo 244Gl Diesel

Before doing anything else do an oil and filter change with the correct viscosity oil for your climate. Also replace the two small o rings on the bottom of the oil filter cap. Use a quality German filter. Re-test.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Oil pressure is at it's worst when the oil is hot and the engine is at idle. It is also very much affected by the viscosity of the oil being used. Do you know what viscosity oil you are using? I would guess you should probably be using a 15w40 diesel oil but a 20w50 diesel oil would give a higher idle oil pressure. The stresses at idle are low so 0.5 bar is fine but 0.3 sounds a bit low. The number after the w in an oil viscosity rating is the rating at operating temperature. Most old diesels require a 40 but a 50 is thicker so will give a higher idle pressure. If you are using say a 30, try a 40 and a new filter before you decide you have a problem.

Diesel oil is black soon after an oil change so if you want to be sure it was changed you must look at the stick before you drive home.

It is normal to keep the coolant down a couple inches in a radiator IF you do not have a overflow tank. If you do have such a tank it should keep the radiator full.

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'97 E 300 D

Iirc, the oil filter in the 200 is a can with a central bolt.
The bolt should have o-rings on it, that redirect oil at a trickle to the bypass element of the filter for soot capture.
Check those o-rings, and as mentioned, check the pressure bypass device for damage.
The early motors also use a thin shaft to drive the oil pump, i have read they sometimes slip.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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My drivers:
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1987 300TD
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I did, I remember checking the oil pressure, but we were moving so it did show 3bar, I should have checked while stationary, but since the car was super cheap and in great condition I did not check further (not like I would not have bought it if I had seen the issue)

I have discarded a gauge issue since the car reacts super slowly when I start moving in 1st gear, which can be caused by low oil pressure.
I have decided to change the oil pump and see where to go from there.
My issue is the same this user described, so I am guessing the problem could be the same https://www.peachparts.com/shopforum/diesel-discussion/60931-300d-no-oil-pressure-2.html

Yep! That is the first thing I tried, no change to oil pressure unfortunately, I am betting on the bearings or the oil pump.

I took the car to a mechanic who changed the oil filter, but unfortunately it did not do anything, I am assuming he took care of the o-rings since he is an expert on Mercedes vehicles, but I will ask him.
The issue is I am getting next to 0 oil pressure at iddle, and it builds really slowly when accelerating, though I do get to 3 when I pass 2.500-3.500RPM, could that amount of oil pressure loss be due to the o-rings?

The car:


Thanks guys!

O rings cause the pressure problem? I don't think so.

Had a 615 in a 220D had pressure like that as I recall, never was a problem. Ran really well.
The oil pump is easy to change on that car and a couple of bearings are accessible through the lower pan.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

The mechanic will replace the oil pump this week and if that does not work we will change the bearings.

This is an issue affecting tons of people from what I have seen in these forums and reddit, so I will make sure to share the progress in case others have this issue in the future.

Why not check a bearing clearance when the oil pan is removed to replace the oil pump?

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I told the mechanic about the bearings so I guess he will check that, I will check with him though just to make sure, thanks for the reminder! Otherwise, I plan on doing a valve adjustment as well once the issue is fixed.

One more question guys, I am replacing the oil pump, the thing is, does that include the oil pressure relief valve? Or is that a different part not included in the oil pump itself?

Here are some schematics I cannot seem to make sense of since my mechanical knowledge is close to 0:



Also de price, in case someone has this issue in the future and wants to have a price reference:

I am quite certain (99.9 %) the oil pump has its' own check valve and will come with it pre-installed.

In post #8 changing the oil filter was mentioned. Was the oil also changed?

Which type oil filter housing does your car have? It should be topside on the left rear corner of the engine. I hope your mechanic uses quality german filters e..g., Hengst, Mahle, Mann or OE MBZ.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thank you so much for taking the time to reply.

It was, we did change the oil filter and the oil itself (items in red), I think he said he was using a Mann oil filter.



And this is my oil filter housing: