So I've read through a ton of threads on here about my motor making a ticking, clacking, or knocking sound. It's not super loud but is very noticeable. The video below is very similar to the sound mine is making.


First thing I did was take the valve cover off to make sure everything was tight, which was the case. Now I'm working on taking off the intake and exhaust manifolds to replace the manifold gasket. I can't get the two bottom bolts in the rear of the exhaust manifold loose. I've tried a sockets and a rachet, wrench, swivel wrenches - and can't get these two loose.

Does anybody have any tips on what worked best for them?

I weaseled my hand through the front under the intake with a 14mm box end, got most of them that way. Pull hard! I just put a new head in.
Also try checking your flexplate bolts haven't loosened up....how many miles are on your motor?

The 4.0 has plenty of good attributes but consistency is not one of them. Pay attention to other 4.0s when you see one in a parking lot or stop light. Some make that same noise and some don't. Some are more subtle than that but the noise is there. The noise on most goes away when rpms increase ruling out rod bearings.

I tried the same thing tonight and just couldn't get enough leverage on the wrench. I sprayed the bolt with penetrating oil and let it sit for a bit prior. I've already checked the flexplate bolts they seemed tight. I tightened them a bit more and thought the noise went away a bit, but it must have just been my imagination. The motor has 150k or so on it.

Also, I'm assuming you meant PUSH hard?

Mine goes away after the RPMs increase a bit. I have good oil pressure also. After everything I've tried it's down to the exhaust manifold with a tiny crack, the exhaust/intake manifold gasket, or a sticky lifter.

Yeah push hard, you know what I meant lol

Haha I had to give you a hard time. I'm done for the night so I'll give it another shot tomorrow.

Can you verify where the noise is coming from with a mechanics stethescope, or just a short piece of hose? Check this out: https://www.cherokeeforum.com/showth...081&styleid=14

Possible lifter issues would sound like they're coming from the middle of the block on the passenger side.

I will try the short piece of hose since I can't quite pinpoint where the source is. I have already tightened the flexplate bolts and looked for cracks.

I'm in the same boat as you. I just picked up another XJ not to long ago and it has that "clack" sound. I haven't checked the flexplate bolts on mine yet though.

Curious to know what you find and what the root cause is.

You can hear mine while it idles, sitting in the cab. As you mentioned, faint but noticeable. As soon as it has the slightest bit of increase in RPM's, you can't hear it.

I just got off work and am about to keep tearing into it. I still need to get the two bottom rear exhaust manifold bolts off, then I should be golden.

It sounds like there may be more than one cause for those sounds.

The vid engine does sound somewhat like pistion slap. Generally piston slap tends to go away when the engine heats up.

The vid engine also has that sort-of timing chain noise. The timing chain slop could be within the 1/2" limit but it may be running dry.

I had similar noises that I thought was the flex plate, but when I pulled the engine the flex plate was not cracked. I pulled the timining chain cover and the chain area was bone dry. Front cam bearing dicked up no doubt. The timing chain had just over 1/2" play.

It defenitely had piston slap.

The cam lobes are like new and the lifter faces are like new. The inside of the engine is very clean because I've been running T6 5W-40.

The engine is in the shop being rebuilt.

Engine has 137,000 miles on it. So much for the 4.0 lasting forever.

That buzzing, almost lake a dragon-fly on a window, could maybe be the Evap solonoid on the firewall.....?

Got it all back together and still making the noise. I drained a quart of oil and added a quart of Mystery oil to see if it would free up a lifter (if that's what the noise is).

My 01XJ with 178k on it sounds almost identical to the video. It was like that when i bought it and like that for the 20,000 miles that I have driven it in the last 14-15 months. Oil pressure is good. Temp. Is good. It runs great. I run 10w-30 High Mileage oil and a Purolator or NAPA Silver filter and it just keeps going. I quit thinking about the noise.