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Unread 11-02-2009, 07:05 PM   #1
cyberlian
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Help! 2.5L Engine knocking sound w/ video

I am a new, first-time Jeep Wrangler owner. I got a great deal on the Jeep due to the aforementioned knocking sound coming from the engine. It is a 1999 Jeep Wrangler SE w/ a 2.5l engine and 139k miles.

We took off the valve cover a few days ago and ran it for a couple of minutes, but could not pinpoint the sound and did not notice anything obvious. It still has good oil pressure (40+) and we have drove it for 300+ miles since the knock started, without any noticeable change in the sound. So, I'm coming to the experts to see if anyone else might have some advice to offer.

Am I looking at a new engine? Or, should I try anything else first? The only mechanic we saw told us to drive it until it quits. Is that the best idea?

Let me apologize in advance for the poor audio. The transition to youtube seems to have added some background noise. You can hear the knock, but it also kind of sounds like the engine is skipping in the video, which it is not. Here is a link to the video:
YouTube - 2.5l Jeep engine knocking sound?

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Unread 11-02-2009, 07:27 PM   #2
2000jeeper
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Sounds just like mine. Mine started knocking the other day to. I need to pull my oil pan down for a leak any way so i will check rods and such them.

If you have a long screwdriver or wooden broom handle put it against the block near the oil pan rails on both sides and the other end up to your ear and see if you can pinpoint a area where it is louder. do the same along the valve cover area.

My noise sounds to hollow to be a rod or main. from the sound yours is makeing it sounds the same as mine
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Unread 11-02-2009, 07:51 PM   #3
tlendt
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If its holding good pressure it might be a wrist pin. I've done engine replacements on two 97s that were knocking (actually one took a complete crap) and it was bad piston wrist pin bores in both cases. The really bad one had nothing left in the #2 bore but a rod and wrist pin; the pieces of the piston were in the pan. Fairly easy to diagnose. Pull one plug wire at a time with the engine running. When the knock subsides that's your bad cyl. Also can drain your oil into a clean pan and look for the tell-tale sparkles of aluminum. The good part is you could do the piston/rod assy "in-frame". Good luck.
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Unread 11-02-2009, 09:28 PM   #4
knomexx
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To make sure it is coming from the engine internals you may want to remove the serp belt and run it for a few seconds and make sure the noise is still there. It sounds like you are probably gonna need to swap the engine though.
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Unread 11-03-2009, 04:08 PM   #5
John1997
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Engine knock in 2.5

I have a 1997 wrangler 2.5L that I just purchased as well for a good deal and it has the exact same noise. Mine did not appear to be as loud. I have it at the shop right now and they have torn it down and it needs a crank kit in it. They are charging me around $850.00 . Does anyone know if that is reasonable or to high?
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Unread 11-03-2009, 04:13 PM   #6
John1997
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Also it is better to just go ahead and replace the motor verse replacing the crank kit? I would hate to spend the money on that and then have other issues. Any advice would be helpful.

Thank you!
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Unread 11-03-2009, 04:19 PM   #7
cmc1
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my engine has been knocking like that for about 40 thousand miles.It has great oil pressure and runs great.probably a wrist pin.I havent heard a 2.5 that didnt do it.they make some noise brand new.I would investigate it further for sure.especially if its running good.
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Unread 11-03-2009, 04:26 PM   #8
hockeyplayer21
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My jeep (when it was my friend's jeep) was making the same noises, and the #2 or #3 cylinder ended up going through the side of the block. I just replaced the motor with a used one that had 80k miles on it. Got it for $350.
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Unread 11-03-2009, 04:27 PM   #9
4.0l sahara
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Pull 1 plug wire off at a time and see if that changes the noise. Then report back and let me know what happens. Also pull the serp belt and make shure it isnt a water pump etc.
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Unread 11-04-2009, 06:46 AM   #10
mdm
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You noise is about the same as what I had with a broken piston skirt.
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Unread 11-04-2009, 07:21 PM   #11
cyberlian
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I went through each of the plug wires a few times with the engine running, but never noticed a real difference in the knocking sound. I haven't pulled the belt yet, but will try that next.
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Unread 11-05-2009, 04:52 PM   #12
2000jeeper
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Drop your pan. I have a feeling you will find a broken piston skirt. That was what mine had and i had the same noise. #4 skirt. Going to NAPA tomorrow to order parts.
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Unread 11-05-2009, 04:53 PM   #13
2000jeeper
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Quote:
Originally Posted by mdm View Post
You noise is about the same as what I had with a broken piston skirt.
Did you short block it or just replace the broken piston?
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Unread 11-05-2009, 05:06 PM   #14
mdm
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Quote:
Originally Posted by 2000jeeper View Post
Did you short block it or just replace the broken piston?
I'm in the middle of a 4.6L stroker build.
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Unread 11-12-2009, 05:08 PM   #15
cyberlian
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Thanks for all the advice. After pulling the oil pan, we found out that it was a broken piston skirt.

I decided to go ahead and get an ATK engine from advanced auto parts. We are also installing a new clutch, slave cylinder, water pump, and exhaust manifold (had a crack). This should hopefully take care of all the major problems for a few years!
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