Chihlidog

OK gents, as posted elsewhere, I'm in the process of replacing the head gasket and all the other gaskets on the top end of my 4.0.

When we got to looking at the manifold, after the head was off, that sucker was so gunked up I couldnt believe it. After an hour or so with carb cleaner and various brushes I got it looking pretty good.

Is this a sign of a larger problem or just normal buildup? I've got about 125k on the engine.

I worked at a Jeep dealership as an apprentice tech for a while, so I have decent knowledge in some areas but there's still a lot I dont know, and this is really the worst buildup I have ever seen. my Father in law, who was a mechanic for 30 years, said the same thing.

Any input? Should I be worried, or just be glad the engine is gonna get the air it's supposed to.

Rmart30

Ive never seen one build up and clog up. Id run some seafoam thru it... 1 can in the gas tank for 3 or 4 tank fulls and then one a month thru it.

Chihlidog

It doesnt show up really well here, but I grabbed a photo last night of the job in progress. The buildup seemed like it was blocking literally half of each intake. The pic doesnt do it justice, it was really bad.



Rmart: I'll grab some seafoam once we get this thing back together and see what that does. Appreciate the tip.

rich

Is it oil or carbon build up looks like oil almost,and there is only 1 spot for oil to come in I think.

Chihlidog

Oil. The stuff is almost the consistency of tar. It's like oil thickened by a lot of dirt and dust. I went through 2 brushes last night cleaning it out, it clogged the bristles almost immediately, I'd get some off, soak it in more carb cleaner, try to get more off, rinse, repeat.

billulsund

I know with my 1989 Renix motor I was having problems with oil blowby getting into the intake. Do you have problems with oil getting on your air filter? That is the only way I can think of that you would end up with that much oil in your intake. I was able to fix it by replacing the vacum line at the back of the valve cover and adding a coalescing filter to the line that goes from the valve cover to the intake. Mine also had a lot of gunk in the intake.

Chihlidog

Never had a problem with my air filter. I change it regularly and it's just dust, no oil that I've ever seen. My throttle body does like to get gunked up but I try to maintain that as well.

I should state that Im not CERTAIN it's oil, but I cant imagine what else it would be. It's thick, extremely sticky, and as you can see by the picture, totally black.

rich

On the back top of the valve cover is a plastic line going over to the intake manifold ,I think that is were your oil is coming in to the manifold for some reason how many miles on the xj.Check the foward line on the valve cover that goes to the air box and see if that is plugged and also pull the valve cover to clean under the baffles.