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Old 06-08-2012, 06:35 PM   #1
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Diagnosis of engine noise

99 wrangler 4.0 5spd

Ok guys, I know this has been discussed over and over but I am stumped and can't find out what it is. I have a light ticking that increases with rpm doesn't get louder just faster, until it drowns out around 2500-3000 rpm. Can't hear it with the doors on just off or with the window down. I've had this for the past 25,000 miles but just now wanting to track it down. Sounds loudest while underneath the jeep around the oil pan, but we all know sound can travel. Thanks in advance.

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Old 06-08-2012, 06:38 PM   #2
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Do you have a video clip where you can hear it well?

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Old 06-08-2012, 06:42 PM   #3
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Quote:
Originally Posted by josh99TJ
99 wrangler 4.0 5spd

Ok guys, I know this has been discussed over and over but I am stumped and can't find out what it is. I have a light ticking that increases with rpm doesn't get louder just faster, until it drowns out around 2500-3000 rpm. Can't hear it with the doors on just off or with the window down. I've had this for the past 25,000 miles but just now wanting to track it down. Sounds loudest while underneath the jeep around the oil pan, but we all know sound can travel. Thanks in advance.
Light sounding ticking from bottom side could be oil pump , hard sounding knock may be main bearing or rod ticking sounds from top side lifters or valves
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Old 06-08-2012, 06:48 PM   #4
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What's your oil pressure at idle and cruise speed?
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Old 06-08-2012, 06:50 PM   #5
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I dont currently have a sound clip, I'm at work. Thanks for the feedback, It's a light tick that just speeds up with rpm. I don't think it's a rod at least not any rod knock I have heard, but very well could be oil pump. Warm idle pressure is 25lbs and cruising at 2500 rpm is roughly 55lbs. Would I be able to see a drop in pressure if it's the pump or are you thinking it's play in the drive?
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Old 06-08-2012, 06:58 PM   #6
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Well typically when bearings go out of tolerance oil pressure drops.. Reason being the gap between the rotating assembly and the bearing offers less resistance for the oil, tighter tolerances offer more resistance. Is the tick fast or slow at idle, that's another way to determine where the tick is coming from.. Usually a slower tick or knock indicates low end, and faster is upper end. Valve train moves faster than the rotating assembly
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Old 06-08-2012, 07:47 PM   #7
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It seems to me to be a slow tick which of course speeds up with rpm but doesn't get louder.
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Old 06-08-2012, 07:53 PM   #8
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You ever down shift it up in the higher RPMs? Where it could've over revved?
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Old 06-08-2012, 07:56 PM   #9
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No, it gets treated like a queen unless it needs alittle extra throttle to get out of a situation. Never have downshifted that hard. I haven't ever been in the limiter if that tells you anything.
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Old 06-08-2012, 08:03 PM   #10
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One thing you can do to figure out which cylinder it's coming from is to disconnect each spark plug wire, rev and see if the noise persists, put the plug wire back on and move to the next.. Do this for each cylinder. If the noise goes away you can narrow down which cylinder it is, if the noise doesn't go away it also can tell you if you have wrist pin noise, or valve train
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Old 06-08-2012, 08:12 PM   #11
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I'll try that in the morning. I guess I have two options, take off the pan and take a look, or live with it till it throws a cast iron fit. Thanks for the help. Hopefully it's nothing to bad, was hoping to get another 150,000 out of it.
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Old 06-08-2012, 08:15 PM   #12
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It may not be horrible, but if it's bothering you to the point of you posting about it here it's worth taking a look, you can probably get a pretty good diagnosis without taking it apart in the Jeep. Might be worth getting a mechanics stethoscope too, they're cheap and help a lot, just put it up to different parts of the motor, it will be louder and more noticeable the closer you get to it
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Old 06-08-2012, 08:19 PM   #13
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Will do, I thought it could be the flex plate but from my understanding that would be much louder and not drown out.
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Old 06-08-2012, 08:22 PM   #14
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I had just thrown a newer 99 long block in my Jeep and got it running the same night but it was making a clacking noise unlike any I had heard before, I scoured the internet for videos, YouTube etc.. looking for something that sounded similar, to no avail.. Used a stethoscope and found where it was loudest toward cylinder two in the bottom end, but it didn't sound like any type of bearing knock or thud, took the engine apart almost completely in the Jeep, valve cover off, oil pan off, timing cover off.. Well I had quite the one off problem, the main bearing girdle was bent right under cyl 2 and the rod cap was coming in contact with it on each down stroke.. I had two big chances to see it, before I put it in and when I had the oil pan dropped, even had pics of it that if I would've paid more attention to I would've seen it... So I ended up pulling the motor back out only to finally see it now that there were contact marks on it.. Felt stupid but I was glad to find it finally lol..
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Old 06-08-2012, 08:24 PM   #15
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Quote:
Originally Posted by josh99TJ
Will do, I thought it could be the flex plate but from my understanding that would be much louder and not drown out.
You don't have a flex plate with a manual, had you mentioned you had an automatic I would've suggested looking to see if it was cracked.. My friend had the problem on his xj..

Also now that you mentioned it, the harmonic balancer can make noises too when they go bad, might be another place to look before you go tearing things up too far
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Old 06-08-2012, 08:28 PM   #16
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That sucks, but atleast you found it. I have been pondering the idea of getting a spare 4.0 and rebuilding it leaving it on a stand In the garage just In case.
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Old 06-08-2012, 08:35 PM   #17
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How would you go about checking the balancer?
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Old 06-08-2012, 08:39 PM   #18
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Just watch it while it runs, listen to some YouTube videos so you know what it sounds like too.. I've seen them go on automatics, which usually causes the flex plate to crack. Never seen it first hand on a manual though
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Old 06-08-2012, 08:57 PM   #19
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Thanks for the jeep knowledge, I will hopefully track it down.
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Old 06-08-2012, 09:06 PM   #20
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No problem man, lemme know what you find out or if you need anymore help
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Old 06-09-2012, 09:28 AM   #21
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Before going too far make sure you check for a cracked exhaust manifold.

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Old 06-12-2012, 07:37 PM   #22
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After checking everything everyone suggested, I found the source to be the bellhousing of the ax15 manual trans! Anyone have a clue what this could be? Makes ticking in neutral and accelerating up to 3rd gear.
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Old 06-12-2012, 07:49 PM   #23
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Throw out bearing, pilot bearing or input shaft bearing, hopefully its one of the first two. Sounds like it might be time to rip the tranny out and have a look. Looks like a good time to replace the clutch too
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Old 06-12-2012, 07:52 PM   #24
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Tob?

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