Yesterday I started the plenum repair on my 94 Dodge Ram. Ran into a few issues but nothing major. After pulling the intake I realized the plenum issue was much worse than I though even though i had no real symptoms other than oil consumption. My motor ran strong with no pinging. The inside of the I take is filthy with oil vapor and residue. My question is how to clean all of this out. I’ve scrubbed it with brake cleaner and a brass brush and it helped but it’s still dirty. I’m afraid to soak it because I pulled the intake with the fuel rail still attached. Will it hurt anything to leave the intake manifold somewhat dirty? If so what’s the best thing to use to clean it?

 

I disassembled mine completely, and took it to the machine shop to be hot-tanked, and walnut shell blasted. It looked brand new when I got it back.

 

I dis-assembled my intake completely and cleaned it as well as I could in a solvent based parts washer. Once it dried completely, I blasted it with glass beads in a bead blasting cabinet. Came out better than new.

 

A little brown on the inside won't hurt anything as long as you get the gritty stuff off. The PCV valve will let some oil through so it's going to get some more in there anyway.
If you really want it to be pretty then you could always buy a Hughes Airgap, it won't have any oil on it when you install it.

If you can't blast it with silica or something like that then I would try out some acetone or a spray called Misty https://www.northernsafety.com/Produ...-Remover-16-oz. My dad uses that stuff at his work to get oil off stainless steel and copper sheet metal because with the price of those chimney caps they're sending off they have to be spotless.
I just looked up the safety data sheet on Misty and found out that it has acetone, toluene, butane and propane in it. I would just give acetone a shot.

 

the thing that works the absolute best is oven cleaner. spray it on all the carbon grease and oil in the intake. let it sit for about 15-25 minutes then come back and rinse it off with the hose. if there is still any build ups just repeat these steps again. i would sooner do this than blast the inside of an intake. plus most people usually have oven cleaner kicking around or it is really cheap at the stores to get.