I am in the process of rebuilding a 4.0 engine for my 1992 Cherokee. Last night, I pulled the intake off the engine thats in the truck, and there is all kinds of nasty black stuff in it that I assume is carbon and oil. It is black and gritty. What is this stuff? Where did it come from? How did it get there? And how do I get it cleaned out? I dont want that stuff going into my new engine!

 

If I had to wager a guess, I'd say the old engine has a clogged valve cover or CCV/PCV system which would lead to oil blowing into the intake from the crankcase. May also have had a poor or never-changed air filter or some kind of intake leak which would allow grit to come in the intake and stick to all that oil. Throttle body cleaner will likely dissolve a good bit, the longer you can soak it the better. I'd guess from the sound of it the air filter had oil stains on the top of it too. Whatever you're taking from the old engine, just nuke it with Throttle Body Cleaner! (straight carb cleaner can destroy the finish on your stock throttle body & other fancy parts so make sure it's TB cleaner)

I started finding oil on my air filter and I found my IAT sensor was all gunked with oil from inside the manifold. When I changed my Valve Cover gasket, I found all kinds of nastiness and clogs so I replaced the CCV breather tubes and grommets/elbows and cleaned out my valve cover drains with TB cleaner. If the tubes aren't brittle with age yet you can clean them with TB cleaner too. The IAT sensor cleaned up with a few squirts too. Runs a whole lot smoother with all that working properly, and I think it got me 1 mpg or so! Mines a 96 with 193K.

 

If you have a machine shop need by you have have it baked/hot tanked and blasted for not a while lot and it will look like brand new.

 

X2--this is what I would do. At the place I used to work at we used this stuff called MAGNUS or something close to that name. It was amazing how that stuff would just eat through anything and leave it so clean. We would put trans cases in it and let it sit for about 15 min and they would come out like new.

 

Ok so I found a buddy that has a bead blaster at his shop that he is going to let me use to clean this nasty thing up. Once its clean, is there a way to keep it from oxidizing, and becoming dull looking? I thought about spraying some clear coat spray paint on it, but thought the heat from the engine might yellow it...anyone have any good info on this subject?

 

Paint it with aluminum colored spray paint....and no Im not kidding. When the paint peels, it will look the same.

Ron