You are 100% correct and your experience mimics mine on two 4.0s.

 

Ok i'll give it a try. Oil has probably already been drained down enough to add it in due to an oil leak I can't seem to find, but that's another story.

 

Then just add the MMO.

Ever read this?




I'd be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF.

Everybody, who doesn't own or have to pay for or perform your vehicle repairs, loves to poke their noggin UNDER the Jeep and come out bearing the false bad news that your RMS is leaking.

Many mechanics, friends, people on Jeep forums who can’t see your Jeep from where they’re at, and good old Uncle Bob seem to enjoy telling you it’s the rear main seal. Has a catastrophic ring to it, doesn’t it?

A simple leak at the back of the valve cover or other source could produce the same symptoms. You don’t need to be a mechanic to figure this out. If you have good eyesight and a dim flashlight, you’re good to go on your own. Don't jump on the RMS/oil pan gasket bandwagon right off the bat.

Almost any oil leak on your 4.0 is gonna drip from the RMS area for two simple reasons.

First off, the engine sits nose-up and any oil will run back to the RMS area. Secondly, the RMS area is also the lowest point on the engine. Simple physics and the old plumber's adage apply here. "$hit flows downhill".

Valve cover gasket, oil pressure sending unit, oil filter adapter seals and distributor gasket, in that order, have to be eliminated as possibilities first.

Revised 02-26-2013

 

Yeah I figured I would start with the valve cover gasket so I replaced it this past weekend. Still has a decent size puddle So I'm gonna work my way down. I hope it isn't the RMS cause it's gonna leak for a while until I have the time to get it on the lift and change it.

 

I bet it's your oil filter adapter leaking. Mine was causing quite the mess in the driveway, and it's all better now.

 

Tried the 3rd gear and 3k rpm thing today. After about a minute or so of it running at the rpm I noticed my CEL start to flash. I was doing about 70-75 mph and staying around 3k rpms. It was already on before due to a O2 sensor needing changed. From what I've read so far, it could. Misfire or something? I'm gonna take it to get the codes read again to see if anything else popped up. Does it flashing mean anything in particular or could be a lot of things?

 

Flashing CEl is a P0300 Random Multiple misfire.

 

I was thinking it was something along those lines. I have no clue when the last tune up was done. It's on my list of things to accomplish soon after I get the already known problems taken care of.

 

You have your priorities bass ackwards.

 

Flashing means imminent destruction of your catalytic converter.

 

That's right. Raw fuel being dumped in there.

My '87 Renix has been clattering the valve train on start up for at least 60,000 miles. It started about 4,000 miles after replacing the lifters.

I have had 3 experienced mechanics look at it. One pulled the valve cover and watched the oiling up top. Oil is flowing well up there, and there is plenty of it.

I use Mobil 1 10W-30 and a WIX filter.

The consensus is that there is just wear up there. It takes just a few moments to take up the slack.

It has 242,000 miles on the original 4.0. I can and would drive it anywhere, anytime.

Did anyone else notice the OP has a 2000 Cherokee? Which has the dreaded 0331 head?

 

The motor was already replaced due to that issue. But was replaced with another of the same year just less miles. Isn't one of the symptoms of that is coolant burning off?

 

I'm already in the middle of the oil filter adapter so once that's finished I'll dive into the flashing CEL.

 

This is the first time I saw it do it. Normal driving I never pass 2500 rpm and it's never flashed before.

 

I'll share my experience with this issue. I have a '97.

Had cold start up noise for about 4 years, but sounded more like a rod knock. Typically, the noise went away after it warmed up, but not always. However, it was always only at/near idle. I expected the engine would die, but it never did. It did get progressively worse though, to the point that it would run a little rough at idle and illuminate the check engine light. Maybe rough isn't the right word, at idle I could feel the rhythmic bump bump bump of a cylinder or two not firing. Codes read misfires in cylinders 1 & 2.

At that point I didn't have any faith in "solutions in a bottle", but did a little internet research and decided to try the method already mentioned, of prolonged driving above 3000 rpm. I also used Sea Foam additive in the oil per the directions on the can. Drove it that way (high rpm with oil treatment) for about a week, the problem gradually dissipated, changed the oil, and it idled as smooth as new again without any more noise. Changed my mind about "solutions in a bottle" for sure.

However, after a couple scheduled oil changes the problem slowly returned. So I've just made a point to add an oil detergent additive every other oil change, which has kept her happy, quiet, and smooth running.

I'm sure the real fix would be new cam & lifters, but this is easy and cost effective enough for me to be satisfied.

YMMV, good luck!