Sound Coming from Master Cylinder/Firewall Region

tmbstn21

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I have an odd fluttering/flapping sound coming from the master cylinder/firewall region heard only from inside the cab. This sound is intermittent when in gear, at a stop/idle. It is sometimes subtle, and sometimes very apparent. At first I thought something was loose inside the dash, but this sound only during idle or coming to a stop (under 5mph). Any thoughts?? I will be posting a video soon.
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NachoRuby

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Auto or manual? Brake master cylinder or clutch master cylinder?
 
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tmbstn21

tmbstn21

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You can here the “flutter” sound each time I shift into D. Again, sound is coming from drivers side dash. Use link if you cannot see vide.
 

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Ball_Ze

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Look underhood for all of your evap system routing - there will be a bright green cap over a schrader valve somewhere in the tubing. Trace the tubing and see if any of it goes to an electric solenoid on your firewall. Could be the evap purge solenoid is mounted there (maybe?) and you're hearing it while your evap system is being purged.
 
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tmbstn21

tmbstn21

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Look underhood for all of your evap system routing - there will be a bright green cap over a schrader valve somewhere in the tubing. Trace the tubing and see if any of it goes to an electric solenoid on your firewall. Could be the evap purge solenoid is mounted there (maybe?) and you're hearing it while your evap system is being purged.
I checked for anything in this area, and nothing. It almost sounds like this sound is radiating upwards from the transmission area. Again this is only at idle or very low speeds (>5MPH), only in Drive.
 

1979WagoneerLTD

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You'll not have an evaporative emissions on your model, as it is a diesel. In any case, try this: crank engine, place in drive. While applying the brake, tip-in the throttle just enough to come off idle, and see if the noise is still there. Do the same in reverse. What we're attempting to do is isolate if the powertrain (engine/trans/xfer case) vibration is causing the noise; in drive, the powertrain will "rock" one way, the opposite in reverse. As the diesel exhaust is located the opposite side (passenger) than the gas burner, the test might help you get a little closer to isolating the fault.
 

Ball_Ze

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You'll not have an evaporative emissions on your model, as it is a diesel. In any case, try this: crank engine, place in drive. While applying the brake, tip-in the throttle just enough to come off idle, and see if the noise is still there. Do the same in reverse. What we're attempting to do is isolate if the powertrain (engine/trans/xfer case) vibration is causing the noise; in drive, the powertrain will "rock" one way, the opposite in reverse. As the diesel exhaust is located the opposite side (passenger) than the gas burner, the test might help you get a little closer to isolating the fault.
Excellent point! I missed that it was a diesel! #facepalm
 
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tmbstn21

tmbstn21

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After finding other threads in the wrangler forums, I found a topic of the DPF weld breaking off the transmission. In turn, causing a knocking sound. You can see a link to a video. The noise I’m experiencing is not that loud, but sounds identical (but I can hear mine emitting from the dash; upper left and behind the AC controls). See here:

https://www.jlwranglerforums.com/forum/threads/2021-eco-diesel-suddenly-much-louder.61174/

https://www.jlwranglerforums.com/forum/threads/transmission-tick-rattle-when-stopped.80735/
 
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