Rattle / Knocking from engine at idle - Cherokee SRT8 Forum
WK1 Troubleshooting / Problems Discussion / Dealer Service If you are having some problems with your Jeep Grand Cherokee SRT8 and need assistance in troubleshooting and diagnosing the problem, this is the proper place to discuss it. Were you treated fairly or poorly at a dealer? Warranty issues? Let us know.

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post #1 of 55 (permalink) Old 04-26-2008, 12:14 AM Thread Starter
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Rattle / Knocking from engine at idle

Hi,

I have a rattle / knocking sound from the engine area when I first turn on my 2008 Jeep SRT8...You can hear it over the exhaust. When you give it a bit of gas, it will go awaya and then come back when rpms go back to resting idle. When I drive down the block and get to my first light (a mile or two) the rattle / knocking sound is gone at idle. It really only does this when the engine has been turned off for a half hour or longer.

Does anybody know what this may be? I have heard of other people having the same problem but nothing was really solidified.

I am using 91 octane.

Thanks!
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post #2 of 55 (permalink) Old 04-26-2008, 12:19 AM
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rattle rattle thunder plattle boom boom boom, don't worry call the car X man.

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post #3 of 55 (permalink) Old 04-26-2008, 06:24 AM
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I added this product to my Mobil1 0w-40. It reduced the valve rattle at cold startup. I can still barely hear it but it is better.
http://www.lucasoil.com/products/dis...tid=2&loc=show

By the way, I brought the bottle of the lucas product to the dealer and they said it would not give any warranty issues.

Some guys have gone to a heavy oil, to fix it too.

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post #4 of 55 (permalink) Old 05-07-2008, 11:11 PM Thread Starter
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This valve rattle is still very annoying. For the first 20 minutes or so of driving the vehicle and idling and coasting with the foot of the gas, the rattling noise does not give the muscle sound of this vehicle any justice. I will have to see what the dealer says and I cannot believe anybody else hasn't *****ed about it on this site....which tells me either I am way too picky or just not sure if this is actually the "valve rattle"
discussed....but it has to be becuase it goes away when engine is warm..
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post #5 of 55 (permalink) Old 05-08-2008, 06:58 AM
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if you can hear it when driving, something is wrong. Mine just makes a light tapping at idle for a couple minutes after cold startup.
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post #6 of 55 (permalink) Old 05-08-2008, 10:31 AM
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i have no valve tapping

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post #7 of 55 (permalink) Old 05-08-2008, 12:29 PM Thread Starter
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Quote:
Originally Posted by SkyeHighSRT8 View Post
if you can hear it when driving, something is wrong. Mine just makes a light tapping at idle for a couple minutes after cold startup.
It only makes the noise if I do not give it gas while the engine is warming up (idle). If I take off out of my garage at cold start up, roll down the window, accelerate down the street and take my foot off the gas, I can hear the rattle noise from the engine. It is not over powering by any means. There is another post out there saying some users have put in a different oil which helps. Maybe it somethin loose in the exhaust?

Maybe I would classify it has a knocking sound... I a musing 91 octane. Like I said above, the ratlle / knocking goes away after the engine has warmed up.

What do you guys think?
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post #8 of 55 (permalink) Old 05-08-2008, 03:42 PM
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I would be concerned, Mine just makes a light tap, and no one has ever heard it, or said anything about it but me and my friend who is also into cars. It's to subtle for most people to notice. Yours sounds worst, or you have better hearing than me...lol.
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post #9 of 55 (permalink) Old 05-12-2008, 05:04 AM
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Mine has been doing this since day one (2007). Take a look at sig and see how strong it runs with minor mods. I have 8,300 miles and still no issues except the noise.

Have tried the 15w50 Mobil one, oil additives, ZMax, etc. Not going to worry about it (it's embarassing at car shows when you go to pull away !).

Have not take to dealer, although it was in for a recall notice and they did not say anything when they started it up inside the repair bays (I was standing there, and heard it clearly).

I've heard every theory from throttle blades rattling to bad lifters, etc. I've put a stethoscope on every single part of the engine and it appears to be from on side, drivers side, up near water pump and throttle body.

I figure if it lets go, that's what a warranty is for. But since it is running so well, I am ignoring it for now.
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post #10 of 55 (permalink) Old 05-12-2008, 10:04 PM Thread Starter
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Quote:
Originally Posted by DavesSRT8 View Post
Mine has been doing this since day one (2007). Take a look at sig and see how strong it runs with minor mods. I have 8,300 miles and still no issues except the noise.

Have tried the 15w50 Mobil one, oil additives, ZMax, etc. Not going to worry about it (it's embarassing at car shows when you go to pull away !).

Have not take to dealer, although it was in for a recall notice and they did not say anything when they started it up inside the repair bays (I was standing there, and heard it clearly).

I've heard every theory from throttle blades rattling to bad lifters, etc. I've put a stethoscope on every single part of the engine and it appears to be from on side, drivers side, up near water pump and throttle body.

I figure if it lets go, that's what a warranty is for. But since it is running so well, I am ignoring it for now.

Dave,

Is there any way you can post a sound clip? I am going to try and do the same. I talked to my "go to" service manager and he said bring it in and we will check it out, worst case a new engine under warranty. IF this is a wild goose chase to track down the rattle / knocking sound, then I don't want to go down that road. Besides this noise, performance is great except for a slight pull to the right now and that it likes to follow the ruts in the road sometimes (especially when braking).

Last edited by Chantililace; 05-12-2008 at 10:07 PM.
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