Crankcase pressure

[race7820000]

I have a 2000 cat c12 with around 680k miles on it. ,there original, it's a day cab and was used locally under a load to were it calls for alot of boost it will leak oil on the ground. Like. It's pushing it past gaskets or seals on the motor. Mainly on the drivers side. But does it all over. I had to put a chain on oil fill cap because it would blow it off. The blow by tube isnt plugged. And when it idles there is hardly any coming out of it.

On a calm day ( no wind) pulling a loaded trailer it uses no oil and doesn't leak. Sometimes a guy can go a cpl weeks without adding oil, but if you get a few days we're it's pretty windy you have to add about a half gal of oil. Because it leaks it out. When it's running or going down road going through gears the exhaust burns clean


The turbo has some black soot, not bad but it's there. The cac side of turbo has some discoloration like soot but it's not bad. Just there. When u take the hoses off and start engine u can smell exhaust coming out of the turbo that goes to the cac. The boost gauge in truck reads normal under a load.

I have a cac tester but need to get an adapter to go on inlet side of turbo so I can test the turbo itself.

When I take the cac hose off the turbo and pressurize the system from there you can hear air leak into the crankcase. So the air is going through the cac to the intake into the cylinders that are open and is somehow getting into the crankcase. When u air system up to 20psi u can fill the air coming out of the oil fill tube hit your hand.

I've had the truck for a year now and it's always done it. Hasn't gotten worse.

Recently it started to have a vibration at idle and under load to were it shakes the steering wheel and the dash. It always ran smooth.

I'm the morning when it's cold from sitting over night it sounds like crap until it gets warmed up.

I am sending a driver today to get a diagnostic computer that I bought. So now I can do a cut out test etc etc.

The truck once it gets warmed up starts super easy, just runs rough.

I realize it could be alot of things, head, ring, piston etc etc. I was thinking maybe it's a bad injector and it has a bad seal or the injector is bad itself to were it pushes air past it in the compression stroke??

Has good oil pressure. Not weak at all and the water temp runs cool. You don't lose oil pressure and water temp doesn't go up under a load.

How can a guy pinpoint what cylinder it is and what it is? Or has anyone had this problem before on a cat?