So the mystery continues. We just motored for 3 or 4 hours with NO problem. But just prior we were making oil (diesel into the crank case).
The chronology and symptoms go like this:
A couple of weeks ago we left anchor
and after about 45 minutes I noticed oil pressure was continually dropping. It always drops as the engine heats, but this was going below low-normal. We stopped and found the oil level on the stick to be about 3x higher than the max line. We had checked oil level before starting the engine that day and it was fine.
We limp into Port Dover, have ~7 litres of oil/diesel removed, install a new lift pump and fill with 30 weight oil. All good.
Engine runs great for another ~12 hrs, and then four days ago during our pre-start checks we find the oil is once again way up the dip stick with the same oil pressure drop.
We change the oil, removing about 7 litres once again (so there must be at least 3 litres of diesel in there) and run for about 1.5 hrs. After that time there was some increase measured on the dip stick. We took out ~4.5 litres of oil/diesel so there was probably about 1 litre of diesel in the oil.
Refill with 30 weight, and then motor
another 3 hrs. Just checked and oil is fine. Going down, as per normal!!
- We had that idle adjustment device on the injector pump fixed with epoxy
(JB weld). The pump was not removed.
- We had an oil leak
, but that was coming from the remote oil filter
cap, and seems unrelated.
- we have a small diesel leak in the return line. Seems to produce no more than a few spoonfuls over many hours, but it is dripping over the block.
- today I took apart the old lift pump. I could see no perforations or problems with the gasket. Locking bolts all seemed snug. Mechanism seemed to work. As you know though, I'm not much of an expert. It's possible I missed something.
Apparently there are only two places diesel can enter the crank case; at the lift pump membrane or via the gearing shaft on the pressure pump. But in both cases you'd think the problem would be consistently there. Our problem is beginning to appear intermittent. There is about 1200 hrs on the engine hour meter. She seems to run well.
Thoughts? Are there any tests we could perform?
theory is that there is a specific RPM
that sets up a vibration which somehow let's diesel through at the pressure pump. The only other thing I wonder about is oil levels. I believe we've not had problems when the oil levels are high.
Why go fast, when you can go slow