3.8 marble noise while idling - JeepForum.com
 
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post #1 of 7 Old 07-09-2021, 01:35 PM Thread Starter
Nick Schild
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3.8 marble noise while idling

Hi, I am having an issue with my 2008 JKUR (with the 3.8l) 150k miles.

Occasionally I hear a strange marble noise while idling that sounds like a marble in a pinball machine that comes and goes.

My best guess is that it is the timing chain, but I tested it by pulling the cam position sensor and it seemed fine.

I had taken it to a Jeep specialty shop and they had it for a few days, but in the end they said that for the most part the engine runs great, but they could not pinpoint the noise as it is difficult to reproduce and to bring it back if/when it gets worse.

Now, I have noticed this noise for at least 9 months, 10k miles, and it has not seemed to have gotten worse, but it still worries me that when it does, it will be bad.

A few more tests that I have ran:
  • Using a mechanics stethoscope, It sounds like it is near the front/bottom of the engine.
  • It doesn't matter if the engine is warm or cold
  • Occurs between 650 (min idle) and 700rpm
  • Usually only lasts a few seconds, but I have been lucky? enough to get it to go longer twice now (see recording below).
  • Unplugging the sparkplugs 3/1/2 does not make a difference. (that should eliminate piston slap, wrist pins, and rod bearings, right?)
  • When I unplugged 1, it sounded somewhat more prevalent (main bearing?)
  • Timing advance is all over the place (in my 2 minute sample in closed loop, it was from 5.5-7.0. Scotty Kilmore says anything more than +-0.5 is a bad timing chain)
  • I tested the timing chain by removing the cam position sensor and rotating the crankshaft. Has about 1/8" on the crank pully worth of slack, within spec
  • Ran MMO the last 1000mi before the latest oil change (no difference)
  • Oil and pan had no visible contamination (pan checked late last year)
  • 5w30 Mobile 1 oils, changed at every 5000k interval.
  • Switched to Mopar filter vs the wix xp (solved the cold start oil sound)
  • Removed the SuperChips 87 tune for a month. Glad to have it back on!
  • Checked under the passenger side valve cover and everything looked great
  • Oil pressure is good as well.
  • I did notice while the oil pan was off, that the rods slid along the crank, but felt tight in the other direction.

I found a few methods to reproduce
  1. start the engine and let idle for 10-30ish seconds, will make the sounds for 2-5 seconds
  2. with the engine running, press on the gas for a few seconds (2K-3K rpm) and after 1-5 seconds of idle, it will make the sounds for 2-5 seconds
  3. with the engine idling, toggle the A/C on and off, 25% of the time, it might trigger the sound.


Attached Thumbnails
screenshot_20210707_181851_86a4f5fd54a027b7e10343977a236f4856c2d126.jpg   screenshot_20210707_181914_3eca9fae5f17e791da9f8e24d669479c5b807be1.jpg  

Last edited by Nick Schild; 07-10-2021 at 09:07 AM.
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post #2 of 7 Old 07-09-2021, 11:57 PM
JLC08JK
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Hi Nick,

Sorry I didn't catch this sooner. I just approved and opened this thread to public view. The attachments caused it to be put for moderation in our system.

Some of our guys with more tech knowledge of your print outs should chime in soon to try and help you out.

Welcome to the club

Jim

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post #3 of 7 Old 07-10-2021, 08:58 AM Thread Starter
Nick Schild
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Thanks Jim. No worries. Hopefully you dont mind the hackery I had to do to post these links. 25 is an awfully high post count.

I am attaching some media of the noise I am hearing. Hopefully someone will recognize it.

Listen closely at the cue markers near 0:14
youtube[dot]com/watch?v=KSdCDdttcMk

This was an audio recording I made a few days ago. Got it aggravated as it lasted for quite a while. Listen for the marble / pinball machine noise. I placed the microphone on the front axle.
drive.google[dot]com/file/d/1q39EILvCn-l5eH_imBN_qihd-sBNPp0z/view?usp=sharing
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post #4 of 7 Old 07-17-2021, 07:23 PM
Thunderstrike
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Have you replaced a water pump, with after market one?

2009 JK Rubicon
2019 Mustang GT Premium 6 Spd DD
Shrockworks Mid-width, Warn 9.5Ti
Skid Row: Engine, LCA & Evap Skid
Rock Hard Gas Tank Skid, Warn Stainless Diff Skid, Uniden 520XL CB
Aeroforce Interceptor, Valentine 1, Baja Designs Squadron-R Pro
Ouray - TJ-8/07
Rubicon - TJ-9/08
Moab x9 - TJ: 4/06, 5/08, JK: 4/09, 5/11, 4/13, 5/16, 4/17, 5/18, 9/21
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post #5 of 7 Old 07-21-2021, 11:06 AM Thread Starter
Nick Schild
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Good news, I ended up taking the timing cover off and replacing the timing chain. It had a deflection of at least 1/2", but luckily it did not damage the cover at all. The noise is completely gone now. While I was in there, I was intending on replacing the oil pump but ended up sheering off 2 different branded impact-rated T27 Torx bits with my new Ridgid subcompact torque gun trying to remove the first bolt and gave up on it. Has anyone else experienced this? I also was unable to get the bottom sprocket off with my pullers nor any of the pullers availble for rent at the auto parts store. It looked good so I left it. Anyway, all buttoned up with new gaskets, seals, sensors, water pump, and hoses, the jeep is happier than ever. Thanks for the input guys!

It was interesting, I was able to easily turn the crank to line up the timing marks. Each time a piston got close to TDC, I heard the compression going out one of the valves and after a short moment, I could continue rotating the crank. With the new timing chain, I cannot turn it over without removing the plugs.

For anyone who is interested, I replaced mine with the Cloyes Timing Chain from Oriellys, as it was the only one in stock near me. It is able to flex in both directions, the OEM one is not. Hopefully, it is not important.
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post #6 of 7 Old 08-03-2021, 06:16 PM
Thunderstrike
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Thanks for posting the cause. I think flex in both direction is good, but not for sure.

I saved this link for future reference.

2009 JK Rubicon
2019 Mustang GT Premium 6 Spd DD
Shrockworks Mid-width, Warn 9.5Ti
Skid Row: Engine, LCA & Evap Skid
Rock Hard Gas Tank Skid, Warn Stainless Diff Skid, Uniden 520XL CB
Aeroforce Interceptor, Valentine 1, Baja Designs Squadron-R Pro
Ouray - TJ-8/07
Rubicon - TJ-9/08
Moab x9 - TJ: 4/06, 5/08, JK: 4/09, 5/11, 4/13, 5/16, 4/17, 5/18, 9/21
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post #7 of 7 Old 10-16-2021, 10:23 PM
Bassman7365
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Note of thanks

Just a note to say thanks for such a great post. You started with a informative synopsis of the issue you're having, followed by a comprehensive list of what you've done to diagnose the problem. Then, you've laid out what the resolution was, in a way that was easily understood. I can't tell you enough how helpful this post was, even though I don't currently have this issue. Thanks again, Pete D
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