jeff39

My father in law called from his RV out on the road and said that the crankcase breather tube has begun dumping about 2 quarts of oil out every 100 miles. He said that it still has lots of power and sounds like it is running good.

We were wondering if he may have cracked a piston or ring. Not sure what would cause the sudden change in oil blow by.

Thought I would check if any of you have any ideas what to look for.

Appreciate your thoughts.



Jeff

dezlsmkr

I have heard that it is by bad rings. But i am pretty sure that the seal can go bad in your turbo and cause to much crankcase pressure or, and i know for sure that if you cahnge the oil and overfill it it will do that. I think the vacum pump seal goes bad it can cause crank case pressure, i would totally freak about it i think there are a number of things it could be i am sure someone will be way more knowlegable about it.

Smkndzl

if the power is there and sounds ok , most likely he lost the turbo and getting excessive blow by. I would take it to Cummins and have them check it out , they can install a drain tube on the turbo with a dual outlet and run it on the dyno , once they are building high blow by , switch the valve over to drain into a bucket rather then the engine and watch the blow by come down to normal if the turbo is the culprit.

infidel

A bad vacuum leak can also cause excessive blowby as the discharge from the pump into the engine block can be increased to the point where it is pressurized.
Could be a very simple fix.

granzow1

I have a problem similar to this want to know anything else anyone can offer about this vacuum pump. What purpose does it serve? In my setup the turbo blows in to the engine but first a vacuum line Ts off then finds its way back to the engine. If this vaccum pump is bad how would it be pushing oil out the blow-by? Any help would be appreciated. Checked the turbo and it is fine. BTW I have a 91 Blue Bird bus.

infidel

Don't know if your bus even has a vacuum pump let alone what it may do.
The line to the turbo is boost pressure to open the wastegate, not vacuum.

Dave Miller

I had blowby a few years ago. I was hauling a horse trailer about 350 miles. several times I stopped and checked oil and added more. On the way back I was blowing oil and splattering the tailgate and trailer.

A few days later I took it to Cummins and they did a manometer test to check for excessive blowby. It came up in spec. At the time I had about 150k miles on odometer. The Cummins tech and I figured I overfilled the oil causing it to puke oil.

Now I always let the truck set overnight before checking oil. It will puke oil if overfilled.

Just my experience with blowby. Do the simple things first.

Dave

granzow1

Thanks guys, I thought I might be just overfilling cause it leaks so fast it is off the dip stick in about 100 miles approx 2 quarts (sometimes even more when driven harder). So I decided to just not fill it and wait, eventually I began to loose oil pressure. I assume that if I am leaking a large qty of oil and my oil pressure begins to drop that it must be leaking more than just the overfill amount.

I am planning on spending the evening investigating the vacuum device. The post below describes the vacuum device as necassary for vacuum assisted breaks. I have air breaks and I'm not sure if they need this vacuum assisted pump or not but I do know there is an air line coming off after the turbo but before the engine.

I have seen multiple posts like the following from another forum
"I think this truck still has vacuum assisted brakes and if the vacuum pump hose splits (the hose runs from the vacuum pump (just in front of the power steering pump) to the brake booster (the big pancake thing behind where you add brake fluid) you can have blowby. "

Can someone explain to me how this could cause oil in the blowby. My impression was that the breather-blowby was for pushing out oil that is in the exhaust/air. Now I could see oil coming in through the turbo/air intake if the turbo seal was leaking and I could see oil coming in to the vacuum/air if the vacuum device had an seal leaking oil in to the vacuum/air supply, but I don't understand how an vacuum air hose leaking air can cause oil to enter the exhaut/air. I think I don't understand the breather/blowby correctly. Can anyone help me understand it better? I have seen some comments where the faulty vacuum is pressureizing the block.

VICIOUS FISHER

HMMM bus/motorhome units with airbrakes won't these guys be running compressors?

granzow1

Ok, I have a vacuum device that sucks air from the intake and then T's 4 directions. 1 hose to the rear for brakes, 1 hose to the side for some air (device didn't look it over too much), 2 hoses back into the engine fairly close to where the blowby exits (not sure if these are air lines or not). I took the vacuum tube off the intake started the bus and the vacuum is sucking air, I put my hand over the hose and got a decent pull. Any help on understanding this would help, probably get back under there again tomorrow.

dieseldemon

Blowby comes from pressurizing the crankcase which blowes oil out the vent(blowby tube) If you have a vacuum pump on this engine it is for the dash doors that controll the heater and AC What brand of oil filter is on the engine if its a Fram, Wix, Napa, or Carquest I would suspect a plugged piston cooling nozzle which will score a piston and pressurize the crankcase My 2 cents

granzow1

Thanks VICIOUS FISHER, yes that air device is infact my air compressor.

I am getting closer. I can see 2 potential problems now. Problem 1 is that the rings needed to be replaced in the engine. Problem 2 is that the vacuum pump is shot and the compresser is letting air past and compressing the air in the crank case.

I can't isolate my compressor because the only lines leading out are air lines and coolant lines the oil is fed to the pump through the block. Any suggestions on how to check and see if my compressor is pressurizing the block. If not any suggestions on syptoms that would reflact 1 promblem as appose to the other.

The next plan is to go for it and start tearing apart the engine, new rings! Probably starting this weekend.

VICIOUS FISHER

the only stuff that requires vacuum on the dodge trucks is heat/ac and brakes oh and cruise too, I think . considering that you have air brakes on your BUS I am assuming you have propane furnace hot water etc. with 110volt generator to run A/C therefore negating the need for a vacuum pump alltogether.UNLESS you also have an Automotive HVAC system. Sorry can't help with testing other than pulling the pump and putting a dummy plate in to block the hole (it is gear driven isn't it? if it is belt driven and not serpentine disconnect belt) run the engine if no blow by then it is pump..........OR take compressor to a diesel shop and have it bench tested. do you have air gauge on bus for your brakes? and has it been showing any erroneous readings? I run compressors on my bigger diesels. NEVER vacuum pumps it's kinda an automotive thing. keep in mind it could also be bad turbo etc. Might be worth the money for a pro opinion. rings....big job. turbo easy job, I'd seriously hope for that.

granzow1

Thanks for the info, yeah I can't isolate the pump for the vacuum cause it is gear driven, thought about just blowing air into the compressor with the bus not on and see if I can feel the air come out the blow-by. By the way the compressor is burried and not easy to get to. I would love the turbo to be the problem but it spins easy, not much play, no signs of leaks. Any other tests for the turbo other than that? I'lll look over the turbo again tonight in more detail, it would be such an easy fix. The air guage has given good reading, when I start the bus I need to let it come up to pressure but there could be a leak in any number of the hoses that run around the bus.

granzow1

So I removed the turbo and the exhaust manifold. The turbo looks to be in gret shape. Spins nice and easy and no signs of oil anywhere. I took the exhaust manifold off and noticed that the first and last exhaust holes look like they are covered in a wet soot while the others look like they are dry soot. I heard that the first and last pistons would be the first to go bad, is this what I am seeing?