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-   -   '83 Mercedes 240D - My W123 Restoration Diary (https://www.team-bhp.com/forum/post-war/173972-83-mercedes-240d-my-w123-restoration-diary-10.html)

Not at all mate. This is not my thread but this is a thread for all things related to Old School Mercedes.

If there is any such group I would be interested as well. So long as the discussion is restricted to all things cars :-)

I feel I have been away from this post for a long time. But I have not been away from my car. So like all car enthusiasts it was time for me to enjoy the therapeutic qualities of an oil change.

The best Oil I could find, and of course a new filter.





Also new oil pan bolt. Again sourced at local spares shop along with crush washer.



Also managed to find these O Rings that maintain oil pressure. These are very important component of the lubrication system and often ignored. Mine were so brittle when I tried to pry them open the damn thing just cracked. I managed to get these at a rickshaw spare shop. Now that's interesting. The humble Bajaj Rickshaw comes to air of the Merc :)



Also changed the rear tranny oil and gear oil. Just to mention, Mercedes recommends Autmatic Transmission Fluid in its Manual Gearboxes. However I use proper hypoid 90wt gear oil.

Good job!
Where do these O rings sit. Part of the pump or so?
Thanks
Jeroen

Like so at the end of Oil Filter Shaft, the two of them.



I believe when these go bad the bypass threshold drops and you leak clean pressured oil and instead of the oil reaching engine some of it drops into the oil pan. SOme more information here. https://www.benzworld.org/forums/w12...ft-o-ring.html

This is the clogged oil filter by pass valve. If the filter clogs badly and thus creates too much back pressure this valve opens and the oil or parts of the oil are diverted around the filter. Better dirty oil going into the engine than no or too little oil.

Jeroen

That is what is labelled 23 in the above diagram. Here is a another one (where it is 19). The lower O Ring ( leads to \'c\', \'fine filtered oil to oil pan\' and the upper one leads to \'d\' which is \'oil return flow bore to oil pan\'.

When these become stiff and non-pliable the pressure release across these O rings stops. This results in a higher pressure across the check valve which then activates earlier in the crank cycle when there is a surge in oil pressure sending more dirty oil to the engine and more clean oil to the pan.



Another interesting feature of the design is the bypass mechanism is part of the filter housing and not the actual filter as in modern spin type filters. I'm sure there must be advantages of the newer design but to me it makes good sense for the car manufacturer to have a greater control over such specifications rather than filter manufacturers. I am aware that different filter manufacturers for the same applications will have slightly different pressure thresholds.

The MBIO has a whatsapp group for various cities and one for Pan India.

Is it mostly about the Oldtimers/Youngtimers? If yes I would like to perhaps join the group.

PM me and I'll put you on. It's for all years and models of Mercedes owners, but I think there is one for just the oldtimers and youngtimers as well.

The best Oil I could find, and of course a new filter.

Does synthetic oil make noticeable difference in W123?

No, not so far as I have heard. Everybody I know uses just mineral oil, some might go for a semi-synthetic. All W123 engines are build to last and they have, just with mineral oil

Well, it did make my engine feel a bit smoother. But there is no way of telling if this is placebo or real. And as always regular change intervals is much more important.

I have a rebuilt engine, new piston, rings, sleeves, top end, so the first oil I ran was a good mineral oil (Mobil Delvac) and then changed over to synthetic. But I'd probably be equally happy to run her on Delvac all the time.

NO offence, personally, I think it is placebo effect. I am always amazed when people report changing to a synthetic oil next engines revs better, FE improves, accelerates better, less noisy. This stuff is akin to snake oil!

Make sure to fit a good oil filter, just as important as oil change if not more important.

Jeroen

I bought the Mobil 1 5W50 because it is among the highest ZDDP concentration oils available. Since ZDDP is one of the primary friction modifiers and ZDDP breaks down with use, I'm not sure if it is just placebo or a real noticeable change. I have no data to support or refute either view.

Maybe we can do an experiment where we have one group of car owners who get an oil change and other do not, and we tell them both that we have changed oil. So a control experiment. And maybe also have scientific instruments that measure engine noise/vibrations. :)

That would be interesting.
On the other hand. These engines have been known to easily clock 500K with no overhaul, running on mineral oil. Why even bother?

Jeroen