My 5.2L Dakota, 77xxx miles, has been idling rough and misfires occasionally on the road. Took my air hat off and noticed oil in my intake. Also crawled under it to see that there was an oil leak coming from somewhere. It doesn't leak bad yet, but bad enough and long enough to get quiet a bit of blow back on my trans. I kinda feel like this oil leak will be separate from the plenium gasket. Could this be related or a totally different issue? I can't quiet figure out where it's leaking from but it's on the bottom of the motor somewhere above the oil pan.

I'm going to order a new plenium gasket set from Hughesengines today. I'm going to go with the complete set, part number 7720r. Will that be all I need to replace the gasket? I'll be changing the plugs and wires soon, as well as, make sure the cats aren't clogged up. No cel yet so in going to take it one step at a time.

 

You should also get the Hughes plenum valley pan--1/4" aluminum plate. The Chrysler valley pan is just sheet metal and will eventually start to leak again. All the oil in your plenum is from a leak--the plenum vacuum draws it in from the top of the engine--the loss of performance is from the vacuum leak.

The intake/plenum gasket kit that Hughes sells looks like the one from Dorman, btw. It's available from RockAuto for $26.xx plus shipping, is very nice and very complete. (I have one on the way for my project engine.) I cut my own valley pan plate from aluminum myself, using the valley pan gasket as a template. Not fun, but possible. There's a guy on EBay who's selling just the plate aluminum valley pan for about $54.xx plus shipping (comes to about $70) Which is how I'm gonna do it this time. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200942695172

 

Hard to tell where your oil leak is on the bottom.

Here's some possibilities. Rear main seal, front main seal, oil pressure sender on the top, back of the engine, distributor o-ring. Also, plenum end seals. Unlikely, but possible the valve cover gaskets. Except for the oil pressure sender, I've replace all of these with the engine in the truck--I have a 96 4wd and replacing the rear main seal is a major job that requires taking the front differential out.

 

I'm going to take care of the plenum gasket first. I'll probably ignore the oil leak for now. I hate to but I'm going to fix one thing at a time. One good thing about it is I don't drive it a lot so it won't really hurt anything to wait a little bit to do.

 

While you have it apart, do some cleaning around the rear of the engine. When I did mine, I replaced the dist. o-ring.

If you do the dist. o-ring, get the engine to the proper top dead center position--line up the marks on the harmonic balancer with the marks on the timing cover--and then mark the position of the rotor to the body of the distributor. The rotor should be pointing to the #1 position on the cap. It's really important to maintain the proper timing.

I don't know what your experience level is, but cleanliness and attention to detail counts. Take extra time to clean the old gasket crap off the intake port areas of the heads and be careful to not drop debris into the engine. I like to use a little Permatex copper RTV around the water jacket ports to help seal them.