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One last hope of identifying this noise

clunk

NAXJA Forum User
Ive been trying to track down this noise lately, have posted a couple times with no replies. I know that diagnosing a noise is hard over the internet, but I can't think of where else to look or where else to ask. Hopefully someone can give me an idea of what to look for. I can search and use to haynes manual to diagnose problems, but I'm not sure what would be making the same clacking noise my jeep is making.

To best describe the noise, would be to say it is a clacking/ticking noise..tak-tak-tak. Not a deep pitch at all, more like a high-pitched clack of two spoons together, only really amplified to the point that people on the sidwalk can hear it if I drive through town.

I have used a long screwdriver held to my ear as well as a length of pipe with a socket extension jammed in the end to try and identify where exactly the noise is coming from, but to no avail. The closest I can get it that it's top end noise, coming from the rear of the engine. I can hear every other normal tick in the engine(rockers moving, fuel injectors etc--they all sound smooth and uniform), but just can't identify the noise from any specefic part of the top end. (ie: I can't identify which cylinder it is coming from). I can safely say that the noise does not come from the bottom end of the engine.

Over the past few days I have really been observing what is happening and when it happens. I have noticed that the engine will run entirely smooth and quiet from cold or warm startup as long as the tempurature does not rise past around 150*. After this, I can hear the ticking start, just barely. By the time the engine reaches it's normal temp at around 205* or so, I can pretty much count on the tacking noise becoming more and more frequent, and louder and louder. The noise is still intermittent, but is far more likely to happen than if the engine is cooler. This probably has to do with oil viscosity. My oil pressure is within factory specs with 10w30 oil, though which has me a little confused.

The jeep has been making this same noise for over 3k, and I don't feel that I'm lacking any power. My idle is a *little* rough, but blips between around 675-700 rpm, which I attribute to a small vacuum leak. The engine has just over 100k, burns 1/2qt of oil per change and does not have any blowby. If the noise wasn't so damn loud, I'd just live with it..but it's finally driving me crazy. The noise always gets louder as the engine heats up, then stays around the same pitch until I get home. Let it cool down to below 150* or so and it'll run smooth and quiet again until the engine heats up again.

So, where else should I look? Is this just the classic case of a failing lifter and I'm looking over it, or is there something else that could be causing the problem?
 
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have you used a mirror to look around your exh an man when your motor is hot an running? It sounds like you have a leak back there to me..have you check all the bolts? Even on the bell housen an starter too...Tighten every thing you can Sorry thats all i can think of
 
would an exhaust manifold get louder and louder as it got hotter though? Usually the ones Ive seen and heard have all been loud until they get hot, at which time the metal expands enough for the crack to get smaller and the leak to pretty much stop.
 
clunk said:
would an exhaust manifold get louder and louder as it got hotter though? Usually the ones Ive seen and heard have all been loud until they get hot, at which time the metal expands enough for the crack to get smaller and the leak to pretty much stop.
yes, but you could have a crack that opens up down by the collector.
As the metal heats up the circumference expands, exposing the crack. The usually crack at the collector, but I'm not sure that it would make a clicking noise, mine sounds more like a tractor.
 
I think more like a "tacking" noise than a clicking. It can be really, really loud sometimes when you pop the hood. it sound like TAK-TAK-TAK, as if something is about to let loose, but it never does.
 
A common noise from the passenger side / rear section of the engine bay can be attributed to the emissions purge valve. It's located against the fire wall, near the top, sort of behind the accumulator. Even though they are somewhat isolated with rubber mounts, they can get noisy at times with the "clacking" sounds you describe. Might want to check that out....
 
My 92 has been making that noise for over 50k miles. No problems. At first it drove me nuts too, but as the mileage went up with no problems, my concerns went down.
 
Does the tapping vary with engine speed? If it doesn't make the sound until the engine warms up, I'd say timing chain. Your description sounds exactly like what mine sounded like, although it wasn't my chain but rather the spring-loaded chain tensioner inside the cover (tensioner only on 2.5 engines, not on 4.0's):

http://www.naxja.org/forum/showthread.php?t=903937&highlight=timing+chain+tensioner

HTH,
Jeff
 
I had this problem with a mustang and it turned out to be a loose brick in the catalytic convertor. It sounded just like a rod knock or heavy lifter clatter. The sound reverberated all over so it was a pain to track down. It's quite normal to have lifter / rocker noises with the 4.0. You can try using an oil system flush on oil change to remove any gunk that might be clogging up a lifter.
 
Jeff in VA said:
Does the tapping vary with engine speed? If it doesn't make the sound until the engine warms up, I'd say timing chain. Your description sounds exactly like what mine sounded like, although it wasn't my chain but rather the spring-loaded chain tensioner inside the cover (tensioner only on 2.5 engines, not on 4.0's):

http://www.naxja.org/forum/showthread.php?t=903937&highlight=timing+chain+tensioner

HTH,
Jeff
it does vary with engine RPM, but stays completely intermittent. The only thing that get's more consistent with the engine warming up is the frequency of which the noise happens, but it doesn't make it happen constantly...it's always like a tak tak tak..then it'll be quiet for a while, then tak tak tak.
I have suspected the timing chain, as it was at the end of the it's allowable limit when I checked it during the RMS job. I'm ready to tear the timing cover off, but I the noise really isn't front end, it's from the back of the block. Am I just hearing things or what?!?
 
I chased my sound all over for a long time, then I bought a mechanic's stethescope....well worth the $10 or so it cost me. With it, I pinpointed it to the timing chain cover.

I should say the noise mine was making was embarrasingly loud/obnoxious, and was constant once the engine warmed up. I wish I'da recorded a sound clip of it before I fixed it.

If it's a rhythmic, clicka-click-click (or CLACKA-CLACKA-CLACK) type sound that varies in frequency with engine RPM, and comes on when the engine warms up, I'd bet 99.99% that it's a timing chain issue.

Jeff
 
the noise mine makes is completely intermittent, and sounds more like a high metal striking metal clattering sound, completely uniform with the rockers moving "tak-tak-tak". Part of the problem with it being intermittent, is that it only last a second or two at a time--just long enough for me to *think* I know where it's coming from, move the stethescope over there then it disapears before I pinpoint where it's coming from.
 
Try feeling the distributor,the shaft can get enough play for the rotor to hit the terminals in the cap,thus the tick-tick-tick.
Wayne
 
Have you tried pulling plug wires while it's running to try and narrow it down to a specific cylinder?

sorry, I have no ideas on the noise - still have one of my own I'm trying to track down and it's driving me nuts b/c I've been told everything from bearings to timing chain to wristpin. One thing I do know is that sound can travel quite well through metal, so just b/c you're hearing it in the rear of the block isn't a guarantee that that's where it is.
 
Piston slap, the piston is loose in the bore at the top of the stroke, it slaps side to side in the bore as the piston changes from a upward stroke to a downward stroke. It could be more than one piston doing this.

My 90 did this from day one when it left the dealer, fixed it last year by rebiulding the engine. It will run a long time like that with no worries.



My $.02
 
Your exhaust is very close to the crossmember and supported by the tranny mount. If you tranny mount is old and oil soaked it will give when hot and let the exhaust rattle on the crossmember. :banghead:
 
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