Hi all,

I recently bought a 2000 XJ 4.0 and as one does with a second hand vehicle, been ironing out all its little faults..although I've kind of left the worst for last.

There has been a tick/knock in the engine since I got it. The guy who had it before me said it was an exhaust leak, I've had it looked at a couple times and it definitely isn't - check out video link (cold start):

https://www.youtube.com/watch?v=kUum...ature=youtu.be

I've read up plenty on this and it many people just live with these noises, unfortunately I don not have this gift...its driving me crazy.

At first I suspected a lifter tick, however I'm leaning more towards the bottom end now. A bit of background on the motor:

- I've done two oil changes complete with flushes and additives, but its still as loud as ever.
- It doesn't really quieten down when the engine gets warm.
- The motor sounds a bit like a steam engine when in lowest gear under strain - gets more pronounced under load.
- When I changed the coil rail recently I noticed that there were no bolt holes for it which suggested that the original head must have cracked and been replaced with older cast, also the tappet cover gasket looks super fresh and there were a couple of illegible stickers on it...I would assume (mother of all f*$@ ups) that the top end has been done, which makes a lifter issue seem unlikely - Would a new top end perhaps put strain on the bottom causing the pistons to 'slap'?

I'd be very interested to hear what you all have to say, any help would be majorly appreciated.

Cheers!

 

Sounds more near the bottom, could be exhaust leak, flexplate, lifters. That is not piston slap, I have piston slap on start up and its for sure a different sound then that.

 

I agree, does sound further down the bottom.
Definitely not exhaust, had it checked by two different exhaust specialist.
Gonna check flexplate tomorrow...seems simple enough to do - would be a godsend if it is, but Im not sure...I think it's either lifters or pistons...or both!
How would you say your piston noise is different?

 

My first thought is an exhaust leak. That you would surely hear through a tube, section of hose, held to your ear.

 

Exhaust leaks at a port on the head have sold a lot of un-needed parts over the years. Try the hose check & see what you find...

 

like I said, I've had two different experienced ears check for leaks and both have confirmed that it definitely isn't leaking...

 

OK then. Don't put a hose to your ear and listen around, won't help.

 

Just checked flexplate, no cracks and the bolts were on nice and tight...so either way I'm going to have to take the F%@*king head off.

Want to do it myself, can anyone recommend a good manual and a link where I can download it?

 

Mileage? Oil pressure? Louder, the hotter the engine?
Are the coil pack threads missing on the head or are the coil pack mounting bolts just missing?
If the original head was cracked then replaced, no telling the potential damage that was done prior to the head being replaced.

Sounds similar to the tick i had on my old 300K mile engine. Stethoscoping shown it was loudest at the rear of the oil pan. Like you, it drove me crazy.

The oil pressure was good. Flexplate/bolts were good but replaced anyhow, no exhaust leaks and the engine started and drove great.
Stumped, i had a couple mechanics including a Jeep Master Tech check it out. They were also stumped.
Replaced engine with a crate engine and no more tick. Best guess was a worn wrist pin.

 

Mileage 160k miles

Oil pressure is good, starts high when cold and as it heats up temp and pressure needles meet in the middle.

Noise quietens slightly when hot, but definitely still there.

The coil pack threads are missing in the head - see pics attached.

A friend told me he had a tick and kept flushing and changing oil every few thousand miles and eventually it went away...I don't think I'm going to be that lucky.

Considering taking the head off and dropping the pan to take a good look at whats going on...may even do it myself if I can get a good manual....anyone know of a download?

 

that sounds like an exhaust leak.

if it were internal you'd see something in the oil. have you strained the contents of the oil filter or cut it open?

 

I think you are going to have to take the 'tin' off of it. Because it is easier, I'd start w/valve cover, just to verify that there isn't a loose rocker/collapsed lifter. If all is well, then I guess you will have to drop the pan. Then check for loose rod & crank bearings. "Plastigauge" is your friend. I'd do the bearings one at a time, rods first. While you are down there under the engine look up at the piston skirts, & cylinder walls, check for damage. Use a bore-scope if available. Good luck, I don't envy you (BTW nice looking rig)

 

Before you go ripping things apart, get yourself a mechanic's stethoscope and try to pinpoint the location of the noise. Harbor Freight sells them for $4. Touch everything that isn't moving with the probe. If you can narrow it down to a specific area, it'll be easier to find the problem when you do open it up.

Ticks can travel around the engine bay and make it difficult to figure out where they originate. I recently had one that alarmed me until the stethoscope narrowed it down to the camshaft position sensor, which had a loose magnet in it. Two screws. Two minutes to swap it out. Fixed.

You need the factory service manual specific to 2000. If you're on Facebook, the "Jeep Cherokee XJ Support Group" has a lot of the FSMs posted for download. Join that group, click "Files" under the pic at the top of the page, and scroll down. I see three uploads there, "00fsm.zip", "2000-service-manual.pdf" and "2000 XJ FSM.pdf". I'm not sure if they're all correct. I can't seem to post a link directly to the group, but it's not hard to find.

If that doesn't work for you, you can always just download a PDF of it from Pacific Coast Manuals for $8. I have a hard copy of the FSM and one of Pacific Coast's PDFs, and they appear to be identical. Plus their PDF is searchable and has the table of contents and index linked. Again, make sure you select the correct year.

http://www.pacificcoastmanuals.com/j...e_manuals.html

 

Thanks for all the advice guys, really appreciate it.

Gonna try all your suggestions before I get stuck in, stethoscope, valve cover and check oil - still have the old oil in my garage.

Thanks for the link to the manual, will make sure I get the correct year too.

Im a novice mechanic, but there seems to be so much info/vids/support online on these XJs that I feel ok about it...only one way to learn right?

 

Following up diagnosis:

So I had a good mechanic friend of mine come around, took the valve cover off and while the engine was running, he'd push down on the rocker arms/valve springs one by one. He said when doing so the engine should spit and sputter and cut out.
Turns out only half of the valves were opening....The other half he'd push down on and the engine would continue to run with no interruptions. conclusion was that it is almost certainly the lifters, which is a major relief.
Will keep you updated on the progress.