I am in the middle of doing the intake manifold seal repair, yes that one hahaha. Anyways the inside of my intake is just black and has a thin layer of oil on it, I presume from the vent going to the valve cover. Of course this means the intake runners in the head are also nice and black. My question is, the engine has 140K miles on it and I am sure ready for a rebuilt in the not too distant future is it worth for me to take the time to clean the intake manifold? or could I be doing more harm then good?

 

Why would there be harm in cleaning the intake? Yes clean it!!

 

Well I have never cleaned one before and not to sound stupid but I was concerned that lets say I couldnt get it clean enough and then a piece of the build up broke off later could it cause damage sine some it appears to be hard carbon type build up.

 

Give it a nice scrubbing in a bath of B-12 and it'll come out nice and clean.
The buildup is not unusual, but is certainly not helping performance.

 

I would probably not worry too much about it, unless there is like a huge clump somewhere. The thin coating of black stuff is probably doing no harm and will just turn black again in a short time. It is good to at least clean the outside while it's off. I used degreaser and a garden hose. Of course then you have to wait for several hours for it to dry.

I would also consider removing all the vacuum barb fittings and resealing those as well. Check all your vacuum lines, it is likely there is at least one cracked, they tend to dry out.

 

I cleaned mine, but I was installing headers, removing the EGR and a bunch of other stuff at the same time. If the EGR has been removed, or you're planning to remove it, the intake should remain fairly clean, I believe. I would probably clean it regardless. What's it going to hurt?