Intake manifold very dirty and oily internally

[rv8pilot]

I have been getting knock sensor error codes for some time and finally decided to bite the bullet and remove the intake manifold, etc. on my 2001 Yukon XL with 233,800 miles. It hasn't been a concern since the thing runs great and there is no perceptible detonation. When I got it last August it had a very bad oil leak which was from the rear main seal which I fixed and it does not leak a drop now. There seems to be some oil consumption, maybe a pint every 1000 mi. or so. The engine was extremely dirty everywhere from oil blowing around (I assume).

So, I pull the intake manifold and besides lots of dirt and oily crud under the manifold I find a lot of very dirty oily crap in the manifold itself and in the intake ports in the heads, and also some raw oil that flushed out during cleaning. The junk in the manifold looked like something you would find caked on a leaking oil pan, really filthy. One thing to make clear, the previous owner did virtually no periodic or preventative maintenance in the 15 years he owned it. He changed the engine oil and fixed what broke but that was it. The first thing I did was to try to catch up on all the stuff that had been ignored including the PCV valve. Now I'm wondering if a bad PCV valve could have been the source of the oil. Or? Anybody have any ideas? Thanks ahead of time.

 

[bottomline2000]

Believe it or not but this considered normal operation for our trucks. It's not burning oil it's injesting it thru your pcv valve hose leading to the intake. The way to stop it is to install a catch can. This will clean up the intake charge from the pcv valve and keep oil out the intake.
http://www.tahoeyukonforum.com/index.php?threads/49716/

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[01ssreda4]

Normal.....even on a healthy engine.

 

[rv8pilot]

Thanks guys, that's a relief. I guess I'm showing my age as none of the engines I built years ago had PCV valves or any of that other crap to slow them down and intake manifolds were clean. Does anybody know the correct way to use SeaFoam to clean up an engine? I'd like to try to get some of the crud out of the oil system at least. Cleaning out the intake would be nice as well although I'll have most of it out as a result of this project.

 

[JonnyTahoe]

I just had my Throttle Body off for cleaning and noticed the same thing with the oil in the intake. Looks like a puddle of oil sitting near the back of the intake I too wondered what causes this.

 

[rv8pilot]

I have an old Sears air line air/water separator that was gathering dust so for the price of a couple of fittings I plumbed it in between the PCV valve and the intake connection for the PCV valve hose. Mounted it securely with a couple of tie-wraps to a convenient hose. It hissed like hell and the engine ran like crap when I started it so I closed the drain valve and all was well. Sometimes its the simple things (like me). Anyway, stay tuned. It it works I'll do something more professional, bongie cords maybe.

An update on the separator: After about 50 miles of mixed city and highway driving I took a look at the plastic bowl of the separator and sure as Shinola there was a bit of oil and little bits of crap in it. So today I made a permanent bracket out of some scrap 1/8" alum sheet and mounted it to the back of the bracket that holds the positive battery cable box. Its kind of close to the exhaust manifold now so I think a heat shield of some sort is in order before the plastic bowl melts. I have an all-metal one just in case.