Kobelco SK200LC-IV, crankcase vent blowing oil

[obleck]

Hello all, SN YQU3362 on this girl, mid-late 90's. Cummins 6bt5.9, though I don't have the engine SN available yet.

(I'm an amateur mechanic, but this one I haven't learned about yet.)

I've got a lot of oil coming out of the crankcase vent hose on the side of the block, on the hydraulic pump end of it.

I'm looking around and it seems it's either a backed up "crankcase ventilation system" (hopefully), or blow-by (hopefully not). The engine does run well, doesn't blow smoke at all, and has oil checked regularly, but this is a new phenomenon. Hopefully there is some filter in there that's clogged?

Thanks in advance!

 

[heymccall]

Oil level good?
Oil not diluted?
Does it puff out the oil filler cap or dipstick, when removed?

 

[obleck]

Oil level good?
Oil not diluted?
Does it puff out the oil filler cap or dipstick, when removed?

Oil seems fine and level maintained.
Puffing: hmmm. Don't think so, but I'll watch for that next time.

In the theoretical event of puffing or such, what would be your diagnosis?

Is there a crankcase vent "part" that should get replaced? I see various versions of breather/filters online.

 

[ahart]

I can tell you from direct experience, they can still run good, start easy and have plenty of power with issues. I’ve got a ISC 8.3L in my service truck, drove it home from Florida (1200 miles) blowing a gallon of oil every 100 miles out the blowby. All 3 rings on 3 pistons were broken in multiple pieces. You’re definitely right to be digging deeper on it though. As heymccall suggested, fuel dilution will cause heavy oil out the blowby, also I’ve heard of turbocharger causing heavy blowby when under a load though I’ve not experienced it personally. Hope you don’t end up where I was:

 

[obleck]

I can tell you from direct experience, they can still run good, start easy and have plenty of power with issues. I’ve got a ISC 8.3L in my service truck, drove it home from Florida (1200 miles) blowing a gallon of oil every 100 miles out the blowby. All 3 rings on 3 pistons were broken in multiple pieces. You’re definitely right to be digging deeper on it though. As heymccall suggested, fuel dilution will cause heavy oil out the blowby, also I’ve heard of turbocharger causing heavy blowby when under a load though I’ve not experienced it personally. Hope you don’t end up where I was: View attachment 253569

Thanks for the insight. When you say "fuel dilution", are you talking about water in the fuel? I was having some of that for sure. Would that lead to broken rings? (ugh....) What about that vs "oil dilution", which I don't have (ie no water in oil, at least insofar as it's black, not gray)

 

[ahart]

Fuel dilution would be a leaking injector or pump seal of some kind putting fuel into the engine oil making it thinner than normal which would cause it to slobber oil out of the crankcase vent. If this were happening I think you would see the oil level going above the full mark on your daily engine oil level checks.

 

[obleck]

Fuel dilution would be a leaking injector or pump seal of some kind putting fuel into the engine oil making it thinner than normal which would cause it to slobber oil out of the crankcase vent. If this were happening I think you would see the oil level going above the full mark on your daily engine oil level checks.

Ah, okay. I'll have to look into that as well. The gauge unit on this machine is admittedly hard to read (though functional). The LCD probably got moist at one point.

If the oil is diluted with fuel for whatever reason, would you say it would stop doing this if at the proper viscosity?

Now that I think about it, one of my guys said that it seemed to be a lot lower on fuel than expected, i.e. there was some unaccounted for fuel. I guess that could be it. Could this happen when it's just sitting, say for a couple days?

Just thinking out loud--there's probably a seal at the end of the pump at the drive gear, and fuel would be on the other side of said seal. So if that seal is out, fuel could leak into the crankcase by way of the drive gears which are on the engine oil side. Sound plausible?

Hmm... I think we're on to something.

The only thing is we just did an oil change after this started happening one day, and after 10-20 hrs or so, it's doing it again. Makes sense....

 

[ahart]

Oil analysis is always a good option as it will catch problems long before you do. Also, it will show trends in wear metals and other contaminants in the engine oil. Basically it will show a small issue getting bigger over time. It’s always good to cut the oil filter open at regular oil change intervals to monitor for metal accumulation as well. I always recommend 250 hr oil changes or at minimum 250 hr samples if you do 500 hr services as I think 500 hrs is way too long to go not knowing if there’s an issue. The dipstick will tell the story on fuel dilution, if it rises above the full mark, you’re likely getting fuel in the oil.