Perkins 4.108 making oil

[Marathon1150]

This topic has been covered before a couple of times but the Perkins 4.108 is a great engine with a couple of factory flaws and I am hoping to learn more about others experience with the engine making oil, or the experience of others who have had a similar experience with other engines.

This story starts about a year ago when we discovered that our previously low oil leakage 4.108 engine had a pool of what seemed to be oil underneath it but the dipstick showed that the oil level was above the max mark. For the 15 years that we have used this engine (currently approx 3000 hours), keeping the oil level just below max would maintain the oil at that level between changes that were done every 100 hours. A quick discussion with a mechanic (by radio because we were in an anchorage in the Sea of Cortez) suggested that diesel may have entered the oil circulation system. I used the "halo" test on a paper towel and the results were fairly clear that his diagnosis was correct. We were able to mostly sail back to La Paz where the mechanic removed the injection pump and replaced some seals. Problem solved.

Very recently however, the engine is both leaking oil and making oil. But the dipstick measurement is going up very slowly. The halo test is not indicating diesel but the amount of diesel intrusion could be so low that it is not detectable with such a crude paper towel chromatographic test. Or is it possible that water is entering the lubrication system and because it is below the oil, not detectable using this test?

My understanding is that diesel can enter the lubrication system of Perkins 4.108's at the point where the injection pump enters the block or, via the mechanical lift pump. Are there other vulnerabilities?

The engine has also just developed a leak from the front shaft of the freshwater pump. Is there a point where water could be entering the lubrication system from that pump? Or from the raw water pump?

Apologies for the long post and grateful for any advice.

[Mike OReilly]

No added wisdom here Jean-Paul, except to say we also experienced the 'making oil' problem a few years ago. Turned out to be the same issue: diesel getting in through the injector pump crank seal. We initially suspected the lift pump, but after swapping that out, we confirmed it was the high pressure pump.

I'm not aware of any other point of ingress for diesel, but I am far (very far) from an engine expert. Hopefully someone else will chime in.

[Marathon1150]

Thank you for the response Mike - I did read all of the thread that you started I believe more than 10 years ago. I found it very helpful in refining my thinking about our problem and as you note, our initial problem was the injector pump. Fingers crossed that it is not the problem again - getting it out and back in, is incredibly difficult. Beneteau must have believed that no engine work would ever be required on this boat so they made engine access ridiculously difficult.

I haven't had a look at the lift pump yet, but will in the next day or two.

[NorthCoastJoe]

Be very careful, the Perkins 4108 that was in my boat put enough diesel into the crankcase to cause it to runaway. Oil level was rising slowly at first, drained and refilled with fresh oil then it dumped over a gallon of diesel in a short time ( less than 15 min) that caused the runaway. The freshly rebuilt injector pump seal failed.

After the runaway it's junk, I saved the starter, raw water pump, and alternator if anyone wants them.

[Marathon1150]

[QUOTE=NorthCoastJoe;3827501]Be very careful, the Perkins 4108 that was in my boat put enough diesel into the crankcase to cause it to runaway. Oil level was rising slowly at first, drained and refilled with fresh oil then it dumped over a gallon of diesel in a short time ( less than 15 min) that caused the runaway. The freshly rebuilt injector pump seal failed. /QUOTE]

Thanks - sounds bad. I intend to check the lift pump and then do an oil change. In this particular boat it would not be a big surprise, but would be a big disappointment, if the problem is with the injector pump. Getting it in and out is hugely difficult and damage to the new seal(s) could certainly be possible.

[Mike OReilly]

Originally Posted by Marathon1150

Thank you for the response Mike - I did read all of the thread that you started I believe more than 10 years ago. I found it very helpful in refining my thinking about our problem and as you note, our initial problem was the injector pump. Fingers crossed that it is not the problem again - getting it out and back in, is incredibly difficult. Beneteau must have believed that no engine work would ever be required on this boat so they made engine access ridiculously difficult.

I haven't had a look at the lift pump yet, but will in the next day or two.

Was it that long ago...? Time flies. Happily, my 4108 has run pretty flawlessly since that event. It would seem unlikely you're getting a repeat of the same injector pump problem. I was told at the time that the lift pump is the most common cause. On our engine, it is far easier to replace.

My injector pump is also incredibly hard to get at. We had to remove most of the coolant system, and shifting other things around. In doing so, we ended up torquing a lot of high pressure fuel lines, creating small cracks that were nearly impossible to see. We spent months chasing down air leaks -- and got really good at bleeding the engine.

Hope you're able to solve your problem soon.

[boatpoker]

If there is water in your oil it will make it a light creamy colour. You don't need the paper towel test to see it.

Diesel in your oil will make little difference to the colour but you should be able to smell it.

[Marathon1150]

Originally Posted by boatpoker

If there is water in your oil it will make it a light creamy colour. You don't need the paper towel test to see it.

Diesel in your oil will make little difference to the colour but you should be able to smell it.

Thanks. The oil is not creamy but remains black. No detectable smell of diesel but I suspect that the amount of diesel, or whatever, very small. I'm trying two things based on advice from a marine engineer friend:

1. water detection paste on the dipstick should identify water contamination (Gasoila paste); and
2. turn off the fuel supply.

The level continues to go up very slowly, despite not running the engine. I'm not sure if this would happen if the diesel lift pump diaphragm has an issue but apparently if the contamination is diesel from the fuel system, turning the fuel supply off upstream from the engine will provide some information. I installed a valve just downstream from the RACOR primary filter so this will be really easy to do.