EBRG

I have a 98 XJ, 4.0 / 4WD / AX15 / 208,000 miles / all stock for now. I have had this Jeep for 3 months. I bought it because I wanted a new hobby and I expected to be dealing with issues. I have not made much progress so far but I am mostly working on coming up with a plan of what to fix in what order, since basically everything will need to be addressed before I can trust it off-road.

The engine has a lot of miles but I would like to hold off on a new motor for as long as possible. It runs great with good power but it has a certain valve-train noise that I have never heard before. From what I can tell maintenance was not horribly neglected, I have seen much worse, but it could have been better. I will do my best to describe the noise and the wear marks seen in the pics.

The valve-train noise I am referring to is only made when you rev the motor above 2,000-2,500 RPM (approx.) and then let off the throttle. The noise starts the second you let off and goes away as the RPM's fall below 2,000. This same noise is greatly amplified when decelerating in gear (manual trans.) from a RPM equal to or greater than 2,500 (ex. cruise at 35MPH in 2nd, let off the throttle and the noise is at it's loudest. If I even touch the throttle the noise instantly goes away as the engine load changes but immediately returns every time i let off the throttle.). This is not a ticking noise. It has the usual 4.0l tick that started during a AutoRX clean cycle. The best I can do to describe the noise, it sounds like a really loud clattering & slightly resemble a worn bearing like noise.

I had the valve cover off to clean up the gasket and to run it with no cover on to look for any lifter issues. I never got to run it since the battery died, my charger broke, and I ran out of time. While the cover was off I noticed some unusual wear on the side of the raised part of the head that the rocker arm stud is mounted in. I only has a crappy phone camera available which is unfortunate because I could have gotten great pics to show this with my normal camera. You should be able to see the wear in the pics just to the right of the pushrods, its worn down to shiny bear metal (it is like this adjacent to every pushrod except the first 3 or 4, which do not have this wear mark). I apologize for writing a novel about this but I wanted to include any information that might help diagnose any problems.

adkodak

Looks like it may have been run low oil and stuff started to rub, as for the noise I have no clue.

wildbill1

I assume you're talking about the sorta triangular shaped marks on the rocker stands. I can't see where the pushrods or rockers could be rubbing. I have no idea what would cause those marks. I had my valve cover off a few weeks ago and didn't notice that on my '99. I notice one thing I saw on mine that also shows up in your pics. My pushrods had the same rusty ring around the top end. It puzzled me. I can't imagine what caused that either.

freegdr

if the push rod bent and did that it would of broke long b4 it bent that far they might be some kind of way the head was held in a machine to drill out the piston hole in the other side for machineing ???

DaddyCat

That's what I was thinking too. A machined surface to allow machining of the other side side of the head.

DaddyCat

That's what I think also. A machined surface to allow the other side of the head to be machined.

EBRG

The wear mark on the pushrods, at least from what i understand, is normal. Yes, I am talking about the triangular marks on the rocker stands and I am puzzled as well. I have googled many pictures of 4.0l heads of various years, casting numbers, original, and reman and from what I can tell none of them have marks like this.

EBRG

Thanks for your insight. I also ruled out a bent pushrod for the same reason plus there are marks on 8 or 9 of the 12 rocker arm stands making it even further improbable. I am not familiar with the machines and tools used to rebuild heads but these definitely do not look like marks from a machine shop and I am fairly certain the head has never been removed. The marks do not have a uniform shape, finish, or size to them. Some are large gouges and some are only slightly nicked. What I dont understand is if these marks are not being made by something contacting them while the engine is running then wouldn't the bare metal be oil stained like all the other metal.

EBRG

The pictures are a little deceiving because each mark, although located in the same exact spot on each rocker stand, is different. Only 8 or 9 of the 12 rocker stands are marked up like this, the first 3 or 4 are normal. The shape and texture is also different on each one.

Thanks for checking the pics out and letting me know what you think. I just find them unusual and I am really curious as to what they are.

EBRG

Any ideas about the grinding, clattering noise i described above? I'm only concerned because it is so freaking loud and its not noticeable at a steady RPM or while accelerating or on the throttle in any way.

Thanks for the ideas everyone

00-buck

timming chain slap maybe ?

EBRG

I was wondering if that could be it. Is it recommended to check the timing chain or do you just deal with it if it breaks?

tannerp89

stick a wrench on your dampener pulley and check the slack in your timing chain, if it moves more than 10*, it's most likely timing chain. although those usually tend to make more noise at idle.

Noisier at high RPM sticks out to me, possible valve float due to weak valve springs?

JeepingDan

That looks like factory markings from a marker to me.

I can't see them coming close to rubbing on anything unless they are seriosly bent.