JKOwners Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
148 Posts
Discussion Starter #1 (Edited)
I have been trying to find this rattle grinding noise for a while thinking it was a heat shield or exhaust but I discovered something new about this noise yesterday. When It is cold it never makes the sound until warmed up also if I let it idle for a couple of minutes and then take off it does not do it but the very next time I get on the gas it's back???

Only happens above 3800 or when I hit passing gear until upshift them it's gone until I floor it again. Only warm and goes away briefly after letting it idle but comes back after been driving shortly.
I have run 87 89 and 93 octane with no change
All heat shields are secure and welds are great
I have no mods accept a mopar locking gas gap that I just put the stock cap on to see if that helps.
This thing only has 7000 miles on it and it drives me nuts! It must be spark knock at high rpm's, only thing I can think of maybe plugs are gapped wrong???
I read another post on evap canister rattle which mine does when thumped on by hand and that seems like a 50/50 split some say or does and some say it's not normal. Would this do it at high rpm's when the vehicle is all warmed up?
Any ideas would be super appreciated!!!! I am going nuts!!!
 

·
Registered
Joined
·
148 Posts
Discussion Starter #2
I checked the exhaust bolts that attach to the manifold and they were very loose but not the cause. I took it for a ride and shifted into 2nd gear and drove to about 4000 rpm heard the noise let off the gas and coasted and the noise was still there until below 3000 rpm. which leads me to believe it is not spark knock.

I think it is the valves rattling! I wonder if it is the 20 weight oil and switching to a 30 would help?
 

·
Registered
Joined
·
46 Posts
it almost sounds like detonation....as if you were leaning out. But if you've run 93 octane and you haven't noticed any performance issues that you should be able to rule that out. I know its been almost a month since you posted, did you figure it out?
 

·
Registered
Joined
·
1,481 Posts
That is def detonation, which WILL destroy your engine if you keep doing it.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
148 Posts
Discussion Starter #6
No I have not found the answer I have brought it into the dealership to have the leaking tranny cooling lines replaced for a 3rd time and the response I got about the noise from the tech and on my worksheet was " Heard the noise but cannot locate or diagnose problem, Noise occurs at high RPM above 4,000 tell consumer it is not recommended to rev the engine past 4,000 rpm's as it is excessively high and not advisable."
So I guess I should never enter the freeway or hit passing gear?
I did try several grades and different fuel stations without any effect. Also I shifted the auto into 2nd and drove until I got up to 4500 rpms and the noise was there and let off the gas and when it was coming back down the noise quieted and went away completely at about 3500 rpms I don;t think it is detonation but I believe what I am experiencing is lifter bleed off and valve noise due to such a thin oil (5w20) It only happens when at operating temperature and if I let it idle at a stop light and take off it's gone until the second time I hit passing gear, almost like it's not getting full lubrication to the valve train. other than this noise it runs great.
I have a case of 5w30 Amsoil and their EA filter and was going to see if that helped but have not tried that as of yet because a 17 year old in a dodge intrepid decided to cross a main road in front of me and I T-boned him so the jeep is now at the body shop! Jeep only sustained damage to bumper and drivers side plastic fender ripped off, No sheet metal, grill or hood damage. So when I get it back I will try a heavier oil weight. There have been several people on this and other forums that have PM'd me and said they had the same noise with recommended oil weight and it disappeared with a thicker weight.
after I try it I will post back on the outcome.
 

·
Registered
Joined
·
156 Posts
Mine did this for a while and it drove me nuts looking for it turned out a factory weld on a heat sheild on the exhaust system was cracked in such a way i couldnt tell by looking at it then i just pryed it away with a pry bar
 

·
Registered
Joined
·
250 Posts
Mine was the heatsheild also That sound was friggn driving me nuts when wheeling where it's quiet.
 

·
Registered
Joined
·
148 Posts
Discussion Starter #10
I went over every single weld and pried at them all if I pry any harder I would break a weld.
 

·
Registered
Joined
·
169 Posts
Check welds on heat shield on the exhaust that runs across from driver to passenger side. Mine has 2 welds come lose just bend the heat shield up a little and rattle gone...
 

·
Registered
Joined
·
60 Posts
Detonation or spark knock generally only occurs during acceleration or load & not coasting. If it happens under no load or coasting I think it's something else.
 

·
Registered
Joined
·
2,135 Posts
mine has this exact same rattle but its constant very low at idle but u can hear it...higher u go the louder it gets....sounds like metal on metal or marbles rattling around like you discribe...kinda hard to track down but my guess is driver/passenger but i cant see anything...im gonna try the heatsheild idea..for a long time tho i thought it was comin from the passenger rear...:bawling: i hope it goes away its really annoying
 

·
Registered
Joined
·
148 Posts
Discussion Starter #14
well I have tried the amsoil 5w30 and it really quited down the engine and seems to run smoother but that noise is still there at high RPM's!!!!:pissed:

I found this video that demonstrates the exact same noise I am hearing. I believe I have a cavitation problem and will look into that some more. there are other forums for different vehicles that discuss this noise and it turns out to be cavitation and in most cases they put a restriction device an the cooling lines that go into the heating core and it solves the problem. Any Ideas on this?

YouTube - Cavitating pump
 

·
Registered
Joined
·
148 Posts
Discussion Starter #15
UPDATE

Bingo we have a winner, It sure was cavitation!

I went to the dealer and bought some antifreeze and they asked if I was low and I told them no but I think this is what is causing the noise they couldn't diagnose and they basically laughed at me and thought I was out of my mind and crazy for even buying the antifreeze.

Well low and behold I came home this morning parked the front end up on some ramps and ran it for a half hour with heat blazing and squeezing the hoses not much bubbles came out but I topped it off went for a ride and the noise was still there but different this time it sounded bad like a bearing noise and sharper. I came home repeated the steps a couple more times getting a few little bubbles and it kept getting better and happening at higher rpm's instead of kicking in when it used. I parked it on the ramps again and let it cool down topped it off ran it for a bit capped it and tried it again noise all gone. the temps are cold here and I think it was trapped air in the heating core. I ran it for a long time and the fan never kicked on so I think it took a while due to the thermostat not getting up to temp and releasing all the air so it took a few tries.

Who's crazy Now, the stealership for not being able to diagnose it:thefinger: or me for infatuating over this?

Anyway noise all gone!:bounce:
 
1 - 15 of 15 Posts
Top