240D oil pump rebuild
 

My '76 240D w115 oil pump seems to be losing its prime after sitting for long periods of time. On initial startup it takes a full 10 seconds to peg the oil gauge. I'm sure it is not the gauge, because the engine is definitely smoother and quieter once it reads full pressure. Once on the road, it behaves quite well, holds appropriate pressure, and doesn't smoke any more than expected. It only sees about 200 miles per year, but I'm afraid to start it up too many more times before I attempt a fix. I know the pump is still available, but I recall seeing somewhere deep in the forums that someone here rebuilt their pump, complete with instructions and part numbers. That thread has proven to be elusive, despite numerous searches. Can anyone help with this? Has anyone here rebuilt their own oil pumps? It should be noted that this is a relatively new issue. Before last year, the gauge took just a couple of seconds to rise to the top. Now it is much longer.

This may not be helpful at all, but just in case... I was having a similar issue and it turned out to be those two little o-rings on the housing shaft that needed replacement. Guess they were releasing some pressure because as soon as I changed them out, the oil pressure gauge would peg a few seconds after started the car.

? Guessing you're talking about the 6 & 7 MM O-Rings in the oil filter's shaft ? .

Those are the two.

Never had to deal with that area thankfully. Do the two o rings prevent the oil draining down when the engine is off if functional? If so you could not develop readable oil pressure until the filter chamber is refilled first.

I am sure of nothing in this area but just some thoughts. More likely wrong but why not just change the old probably bad very tired old o rings and see what results? I certainly would before digging into the oil pump. Many oil filter setups if not most have an anti drain back valve.

Those o rings are probably well over any reasonable service life expectation of use anyways. New oil filters of some brands even include the o rings I think.

Actually the first poster to respond pointed out that indeed they created an identical problem on his car.

Oil Pressure Issues
 

Thanx Shern ;

I have the very same issue in my '82 240D and was wondering what to look at next since the rest of the engine is essentially new .

I was wondering if there was an anti - drainback valve in that canister .

Thanks, I changed all the o rings on the last oil change. It's due again, since it's been well over a year (closer to two). No rush because it's only been about a thousand miles. When I change it again, I'll change the o rings too. The oil pan is dented--been that way since I got it, and I have a new one to put on. Since I'm doing that, the oil pump is right there. That being said, I'll remove the filter canister first and confirm that the o rings are in there, and in the right place.

I am wondering the same thing about the oil pump. Seems a check valve, if there is one, may be getting weak. The car only has 76k miles but sat in a garage for many years.

OM616/617 Oil Filters
 

? I thought they were all the same ? .

Mine too is out side the engine, left rear .

The OP has a W115= different in many ways.

Halfway through 1976 they changed to the w123. Mine is a March 1976, still a w115. Confusing sometimes to get parts, you really have to enter the vin number, especially when ordering from the dealer.

Does the oil filter housing have the spring at the inside bottom and both filters in it i.e., the primary and the secondary. Check that the camshaft oiling tube is in place, not loose and creating a loss of pressure.

How bad is the dent in the oil pan? Does it seem bad enough to be related...causing a restriction in the rubber foot on the oil pump pick-up screen?

Also check that the pump is bolted up tightly.

Good luck and keep us posted!!!

I too thought that was a gas engine only set up of an early vintage. You might consider posting this problem in the vintage section of the site as well. It also was mounted horizontal as well. I never owned a 115 diesel.

Or is it basically the later diesel filter set up just mounted lower? Well since it has O rings in there it is not like the gas engine oil filter setup. After some thought it possibly is just the same type filter housing mounted in a different location on the block.

I guess I still learn something every day. This model in diesel was really scarce even when new in my current area of the country. At the time the 114 gas models sold fairly well. I saw no visual difference between the 114 and 115 models.

Anyways it probably still is just the o rings. A pretty easy fix.

Still there was a 114 coupe with this engine in it sold used locally about ten years ago that sounded factory. Special order I wondered or converted?

Thanx for the clarification Rich ! I'd missed that .

Yes the filters and spring is all there. I even checked the schematics book when I put it back together to make sure. The pan is dented enough that it might cause an issue. It is also possible that it was made worse when I raised the engine recently to change the front vibration damper. I plan on pulling the pan this weekend--or at least not starting the car until after I've had the chance to do the work. I'll keep everyone posted....