Crankcase Pressure

[Steve Frazier]

My Cat 248 has suddenly developed a severe case of blow by. There's oil coming from under the valve cover and oil blowing out the muffler at high rpm. It came on all the sudden, the machine has a 76hp Cataperkins, I don't know what number it's assigned. The conditions just before this happened was rain followed by extreme cold, this might have something to do with it. I don't have covered storage for it, it sits outside so rain runs through the radiator down onto the engine. I had to thaw the alternator to run the machine, it was frozen stuck.

Does anyone know of anything that could freeze up and cause this problem?

 

[Shifty]

Steve Your icing and freezing rain issues sound filmier to me. Are you sure that it is engine oil you see. See my post below

Cat radiator leaks. post#3

https://www.heavyequipmentforums.com/Forum/showthread.php?t=10725

 

[Haul-Pak]

Cataperkins

Hey Steve, All Perkin's Breath alot after a while. How does it start and run?

 

[John DiMartino]

Hey Steve, All Perkin's Breath alot after a while. How does it start and run?

If he slowly developed this I'd agree,but overnight,Id say something isnt right. The oil out the muffler is bad,I'd suspect possibly turbo seals on the exhaust side if its runnign smoothly. A head gasket failure could cause this as well. A frozen plugged crankcase vent can cause the pressure to go somewhere as well.It shouldn't go out the muffler though.

 

[Haul-Pak]

If he slowly developed this I'd agree,but overnight,Id say something isnt right. The oil out the muffler is bad,I'd suspect possibly turbo seals on the exhaust side if its runnign smoothly. A head gasket failure could cause this as well. A frozen plugged crankcase vent can cause the pressure to go somewhere as well.It shouldn't go out the muffler though.

Yeah I never read the Post correctly ...

Pretty Hard to help without being there ... Your gonna have to start pulling stuff off and having a real look ..

 

[bill onthehill]

with those issues I would lean toward broken ring or cracked piston. try a compression test on all cylinders and see if they are the same. while the weather did suddenly change I can't believe it would bring on these troubles unless the head froze and cracked. any anti-freeze in the oil? it sure does not sound cheap to fix and snow is coming. Bill

 

[Steve Frazier]

It's starting and running fine except for the oil problem. The machine has about 1700 hours on it and most of those hours are at 1/2 throttle or less. Oil is black, no sign of water in it. I'm going to tarp the engine compartment tomorrow and put a 500 watt light in there and hope for the best. I can't tear into it with the snow coming.

 

[John DiMartino]

I hope you guys are wrong, I think he may have a plugged crankcase breather,plugged or frozen shut with moisture. This could cause the backpressure to pressurize the turbo thru the turbo oil drain tube,pushing oil past the exhaust side of the turbochargers seals.Hopefully thats all it is,and fixing the breather,and possibly a reman turbo will get him going strong again.If its the breather,just fixing that may alow a lot of the oil coming out the exhaust.I didnt think 1500 hrs was alot for that engine,I know Steve follows Cats recommended maintenance intervals to a T or better.

 

[Construct'O]

Steve i'm sorry i can't remember for sure the reason,but my Cat mechanic discussed this issue about a Cat skid he worked on last year.

It was about cold starts in outside conditions!You need to try and get the machine inside if possible.This is different then your problem ,but something to think about and maybe the start of it happening to you?

Anyway the customer started the machine when cold and went back inside to let it set idling to warm up,when they cam back out it had locked up.So might want to stay with the machine when cold and letting it warm up.

Pretty sure it had something to do with the oil sump screen and thick oil.I think he said something about them updating to different screen???So with that you might need to go to lighter weight oil.

He commented that he had more problem with the small size Cat skids then the bigger ones.Thats about all i can add.Except i would be getting a cover over your machine and heat to it.Good luck:usa

 

[special tool]

It's starting and running fine except for the oil problem. The machine has about 1700 hours on it and most of those hours are at 1/2 throttle or less. Oil is black, no sign of water in it. I'm going to tarp the engine compartment tomorrow and put a 500 watt light in there and hope for the best. I can't tear into it with the snow coming.

I have been thinking about this.
I am VERY experienced with turbochargers, I don't mind telling you.

The most important question for diagnosis is temperature.
What is the temp of the engine when you see liquid oil out the exhaust?

A leaking turbocharger dynamic seal will give you a smokeshow/stinkshow (not liquid oil) when the engine is HOT, because of very high EGT in the turbine housing.

When the engine is very cold at startup, the oil pressure relief will be open, because the oil pressure will be VERY high, this could show you liquid oil out the exhaust (if turbo seal is bad) for a few moments because the exhaust configuration is relatively short on your machine.

Also - keep in mind that a dynamic turbocharger seal is called that because it is dynamic - it changes with temperature. It is another part of your engine that needs to "warm up"

However, none of the above explains the pressure in the valve train - which is drain only - outside of journals, of course.

Are you really sure the engine sounds good?
Do you have ice on the OUTSIDE of the head?
Can rain have gotten INSIDE the muffler (ice on rear of exhaust valve seat)?

 

[Cmark]

Is it a 248 or a 248B? From memory, the B's have a crankcase gas recirculation system with a one-way valve that gives trouble. I think there's a rework for it.

 

[Steve Frazier]

It's a straight 248. I just got in from plowing snow, I'm going to take a better look at it in the morning with the information posted here in mind and try to get a better description of what's happening.

 

[Iron Horse]

Running it with the filler cap off will tell you if it excessive crank case pressure . I would stick a bit of open cell foam in the filler hole to stop oil being thrown out and give it a bit of a work out . I would also check that the drain hose/pipe on the Turbo is clear and not kinked etc. if this happens the Turbo will flood with oil . This amount of oil will not be affected by Turbo heat and will come out the chimney raw with little or no smoke .

 

[special tool]

Running it with the filler cap off will tell you if it excessive crank case pressure . I would stick a bit of open cell foam in the filler hole to stop oil being thrown out and give it a bit of a work out . I would also check that the drain hose/pipe on the Turbo is clear and not kinked etc. if this happens the Turbo will flood with oil . This amount of oil will not be affected by Turbo heat and will come out the chimney raw with little or no smoke .

If you kink aturbocharger drainline, you pressurize it internally to 5 bar or so (OPRV setting) this forces oil through the turbo exhaust seal into the turbine housing - where it is hot.

The center section of a turbocharger CANNOT hold 5 bar pressure outside once it leaves the journal bearings.

 

[mackman]

Clean out the breather vent for the crank case. I have had this happen to me befor. If the engine vents a lot of moisture the tube or cap will freeze closed.

 

[Steve Frazier]

I finally had some time to really dig into this thing today. I traced out the breather hoses and located the breather vent, it's bolted to the side of the block under the intake manifold. I had to pull the air filter housing and one of the intake manifold bolts to get the breather loose, when I did I discovered both the breather and the hose going to the air intake line to the turbo full of ice. I've got the breather sitting on the wood stove now thawing and drying, I'll pull that hose and blow it out.

I'm hoping this is the extent of the trouble and that no permanent damage has been done to the seals that are leaking. I'll keep you posted...

 

[Steve Frazier]

Wahoooooooo!!!!

Got it back together, no smoke, no oil blowing out the exhaust!! I ran it for about 20 minutes, part of that at full throttle. I've got a job tonight where I'll be working at full throttle for an hour and a half, this will tell for sure.

I was sweating bullets here, the turbo seals sure did seem like a distinct possibility and funds are so short the repair kit would put a real hurting on me. Thanks to everyone who replied, I'm sure glad it was a simple fix.

 

[Iron Horse]

Good news ....

If this is an ongoing problem with the extreme cold , you may need to adapt a Nascar type tappet cover breather filter to the oil filler lid or rocker cover .

 

[Iron Horse]

For some reason i could not add this picture to the previous post .

 

[Steve Frazier]

My buddy John above had suggested that, I was going to go that route if I didn't figure it out for tonight.

I just got in from snowblowing and the machine worked just fine, no smoke and when I got home I took a look inside the engine compartment. The oil that was sitting on the head has started to dry off and there's no additional oil leaking from the muffler joint. I think I got away here without damaging any of the seals.