I need some help trying to figure out my blowby issue on my 92 f150 5 liter. So to start off my trucks got 109k miles on it, don’t know much about the history because I bought it off of Facebook marketplace. Main issue I’m having with it is my air filter is soaked in oil and I have oil in my airbox. I think this may be caused by blowby as in oil is being pushed through my vent line attached to where my oil filler cap is. So first thing I did was a compression test, all my cylinders where at 150 PSI expect for 2 which where at 145 so seems like my piston rings are sealing fine. Next I checked my PVC valve to see if it was clogged, my old PVC valve was fine but I bought a new one just incase because they’re really cheap. Also my oil filler cap has this milky residue on it from moisture getting in my engine, I noticed this on the old and new PCV valve, i pulled out my new PCV valve after only a few minutes of running and there was the milky residue already on it. Pretty sure I don’t have a blown head gasket because my oil still looks really clean and the last oil change I did on it was clean, no signs on coolant getting into my oil so not sure where this milky residue is coming from or how moisture is getting into my engine. I’m pretty sure I don’t have a blown head gasket because all my cylinders are 145+ PSI when I did my compression test. I also checked my PCV hose to see if it was collapsed or clogged and it looked pretty new and wasn’t clogged. I have no clue why I’m having so much oil in my air filter box and why there’s milky residue on my oil filler cap and PCV valve so if anyone has any clue that would be a big help! Thank you guys

 

Make absolutely sure the breather filter, breather plumbing and PCV plumbing are in good shape. The PCV hose should be of the reinforced type to prevent collapse. Make sure the fitting where the PCV connects is clear. I would run some stiff wire into it to make sure. I always use a Motorcraft PCV. It makes a difference. Verify that you have 18-22 inches of manifold vacuum at idle. If you are not using coolant, the milky stuff you are finding (make sure your engine is running at the proper temperature) likely is from short trip driving and poor engine breathing. I would do an oil/filter change if it is nearing do.
I had the same issue with my 4.9, everything checked good.My breather connection going into the valve cover was actually being blown out of the grommet. I was not going to rebuild the engine and emission testing did not apply to my old truck. I finally put a higher capacity PCV onto the engine with a slightly larger port. That solved all my issues. Do that only after verifying all else is good.