Also, check the PCV. It might be stopped up. I was wrong about what I said about a head gasket. A blown head gasket could be the cause of it if the gasket let some coolant or water from the coolant passage or water jacket into the cylinder. If water or coolant did get into the cylinder then it could cause the connecting rod to bend, or it could cause the piston to eventually get a hole in it to cause compression to drop which would mean that crankcase pressure would rise.
Hi there A head gasket could cause extreme crank case pressure if it was blown out at the compression seal to a crankcase opening I have never seen it happen but it could. Why do you feel it's caused from the headgasket? We have had a couple 5.9s score the #1 cyl and piston real bad I'm sorry it was 3 of them we came to the conclusion it was from the engs idling to long at to low Rpm we fixed them and stopped idling so long and when we did we throttled them up over 1200RPM's and have never had another problem. any time that eng is running too cool the #1 cyl is the coldest. When these cyl would score we would get real lot of blowby even to the point of blowing out oil. Now the other thing is I've seen more blowby on the 5.9 then other engs I don't know if i'm goofy or not. If you feel the blowby is real bad pull the head and both problems can be cked at the same time. GOOD LUCK
If a B5.9 headgasket goes, you WILL know it. They typically leak water first, then oil. I cannot imagine how you could blow a head gasket and get excessive blow-by on this engine and not have a BIG coolant leak as well.
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Hi again ModMech I do believe you are right I just looked at a blowin head gasket I have here in the shop right now and the only way to the crankcase is through the pushrod holes and you would almost have to go through the coolent passage to get to it. This perticular head gasket went from compression seal to water jacket and believe me we new it it blew coolent everywhere Thanks for correcting me on that.