240D oil pump rebuild

[76w115]

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.

[Shern]

Originally Posted by 76w115

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.

[vwnate1]

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

[Shern]

Originally Posted by vwnate1

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

Those are the two.

[barry12345]

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.

[vwnate1]

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 .

[76w115]

Originally Posted by vwnate1

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 .

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.

[Diesel911]

Originally Posted by vwnate1

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 .

I don't know if that is so on the 1979 but there is an anti-drainback valve in your 1982. It is in the bottom lower 1/4 of that tube that attaches to the Oil Filter to Cap.

[76w115]

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.