puking oil out blowby tube need help

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06cumminz

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Apr 14, 2010
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I have a 96 12v cummins 4wd 5 speed. I bought the truck about a month ago and everything has been good, it had quite a few oil leaks from tappet cover, front seal, rear main and front case to block gasket, so i fixed all of them and put a hamilton cam in while i had the truck apart. Truck runs great until it started puking oil out of the blowby tube, the truck has 278k mile and was all stock until i got it, I drove it to dallas and back this past weekend (i live in san antonio) so about 600 miles round trip. My truck went through 6 GALLONS of oil to drive there and back. I have checked for vacuum leaks and have none. the truck idleing and warmed up has 0 blow by and sounds like a sewing machine, what else could be causing this? im at a loss
 
One vacume line can cause this from what I have had happen to me in the past. Does all your controls work on your heater / ac vents, bi level, floor defrost?
 
Um, i would say you have a bigger problem than a vac leak. Like a hole in the piston or some really bad rings. You are pressurizing the crankcase. So oil has to go somewhere.
 
all vacuum operated controls work, defrost, vent cruise control and brakes. Im beginning to think i need to pull the motor out and go through it which isnt cheap
 
i just did a compression test
#1-340psi
#2-410psi
#3-370psi
#4-400psi
#5-360psi
#6-360psi

All those numbers seem to be decent to me, they do vary a little bit but shouldnt be bad enough to make it puke oil.
 
Just to help you for the time being put some breathers in the valve cover. It'll help with venting the pressure. One of my trucks has a lot of blow by. It ain't a permanent fix by any means. You got something else goin on.
 
The turbo could drive high blowby if the seals are going bad. Have you checked it for oil carryover?
 
That's ridiculous.

The vac line is new info for me. How does it pressurize the crankcase?

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hahah ya fresh oil changes are nice every 3-5k miles, turbo is in great shape. the only place the truck is loosing any oil is out the blow by tube, i have fixed all other leaks. I have built several 12v cummins motors and i am lost right now. Would a higher lift cam cause the tappets to sling oil higher or a larger quanity or something retarted that i dont understand and thats why is coming out the blow by tube. im just throwing things out there to try and figure this out without pulling the motor
 
i havent driven it long enough at low rpm to see if it does it, i drive 2 miles to work or drive into the nearest city and ive been cruising 70 so its about 2100 rpm and its doing it
 
What's the oil psi reading at the filter?
Click to expand...

I need to put the injectors back in it and then ill hook up a pressure gauge at the filter housing and see what i get
 
When you changed the cam, did you clean or change the filter material in the stock tappet cover? If it's covered in grime and the oil bypass is stuck, it will pump the crankcase dry! Path of least resistance and all.
 
Could be the reason behind the leaks to start with, and now that the leaks are fixed, well you know where I'm going with this!
 
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