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Unread 03-05-2008, 02:57 PM   #1
weslaine
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Lifter Noise vs Piston Slap

Hey fellow Jeep Brother and Sisters,

My 97 Wrangler has been making a tapping noise for over the last 8,000 miles. It has gradually gotten worse. I took it to used jeep dealer/mechanic - I thought I had a bad lifter/rod. He pulled the wires off two of the injectors while the motor was running - the tapping noise lessened but did not go away. He said this is more than likely a case of piston slap. How can I be sure?

My choices are: let it go and see what happens; pay him to pull the oil pan and valve cover,measure everything and check the lifters; pull it completely apart and remachine the motor & new bearings, or just put in a used/new motor.

Any recommendations? 162,000 miles.

Thanks

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Unread 03-05-2008, 03:54 PM   #2
never monday
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pull the pan your self and look up in there. There have been a rash of broken pistons. If one is broken you can get a used rod and piston and new rings for one cylinder, a gasket set. Then put it together and keep driving. If you ignore it, eventually it'll get worse and could punch o hole in the cylinder wall.
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Unread 03-05-2008, 07:13 PM   #3
weslaine
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Thanks Never,

I'm mechanically inclined but not a mechanic. I'm not sure if this is something I can tackle on my own.

Anyone else have experience with Broken pistons? Piston Slap?

Is it better to buy a remanufactured crate motor or have my current motor rebuilt?
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Unread 03-05-2008, 07:48 PM   #4
mich99TJ
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For what its worth, my 2000 Neon with the 2.0 liter 4cyl has had piston slap almost since it was new. It now has 125K on it, and still makes the same noise every morning on cold starts. I have been told multiple times by reputable sources that its innocuous, just like lifter noise. At first I didn't believe them, but time has proven me wrong. Just my experience, you'll want to draw your own conclusions.
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Unread 03-05-2008, 08:14 PM   #5
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Hey Mich,

My mechanic told me the very same thing. He said that I could probably run the motor for another 100,000 miles with the slap.

The difference is my slap is very loud when the motor is cold and ony slightly gets quiter when running at tempature. I would say even when the motor is hot the slap is still loud.
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Unread 03-06-2008, 07:47 AM   #6
mich99TJ
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At this point with your high amount of mileage, you are facing the decision 1) replace the engine, 2) rebuild the engine, 3) wait and see what happens.

The first 2 options are expensive, the third just prolongs the situation. It just depends on your own feelings on the risk of having the engine give up on you. I would personally ride it out since I'll probably have to replace it anyway down the road. On the other hand, if you are uncomfortable with the noise and it gets progressively worse, just address it now.
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Unread 03-06-2008, 09:26 AM   #7
tebriel
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tapping is usually a lifter, but if your jeep sounds like a diesel then it's piston slap.
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Unread 03-06-2008, 09:38 AM   #8
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Quote:
Originally Posted by weslaine View Post
The difference is my slap is very loud when the motor is cold and ony slightly gets quiter when running at tempature.
Sounds like piston slap to me. I've had a few new vehicles with piston slap when they were cold, it's pretty common these days. If you've got 162,000 miles you're gonna have a few noises! I'd forget about it and drive it.

I cant remember what kind of pistons we put in my Jeep when we rebuilt it, but the piston slap is pretty loud at startup, it goes away at operating temp though.
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Unread 03-06-2008, 09:41 AM   #9
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If you want to rule out valve train, remove the valve cover (if you dare). You can do some diagnostics there with the engine running. All I ever did is put my thumb on each rocker while it was running and it is very easy to feel if there is a problem.
If you can't find anything there, then look further down (or get someone else to).
Just an idea.
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Unread 03-06-2008, 01:04 PM   #10
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you can also use a stethoscope and place it on different parts of the engine to determine where the noise is coming from. you can also use a socket extension, it just doesn't work as well.
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Unread 03-09-2008, 10:37 AM   #11
weslaine
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Quote:
Originally Posted by tebriel View Post
you can also use a stethoscope and place it on different parts of the engine to determine where the noise is coming from. you can also use a socket extension, it just doesn't work as well.
Thanks Tebriel,

The mechanic put a stethoscope on the motor and isolated it to around the head. We both thought it was a lifter until he pulled off the wires to the first 2 fuel injectors and the knock didn't go away.
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Unread 03-09-2008, 10:45 AM   #12
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Quote:
Originally Posted by tebriel View Post
tapping is usually a lifter, but if your jeep sounds like a diesel then it's piston slap.
so that's what that is...
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Unread 03-10-2008, 08:17 AM   #13
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Quote:
Originally Posted by weslaine View Post
Thanks Tebriel,

The mechanic put a stethoscope on the motor and isolated it to around the head. We both thought it was a lifter until he pulled off the wires to the first 2 fuel injectors and the knock didn't go away.
yeah but would killing the power to the cyl really get rid of lifter noise? if it were the injector being super loud, it would stop that. but your lifters are compressed by rockers attached to push rods. right? let me know if i'm thinking wrong.
-teb
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Unread 03-10-2008, 08:45 AM   #14
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Be sure that it's not as simple as an exhaust gasket or cracked manifold/header. I have seen this misdiagnosed before.
I'm sure you've ruled it out already, but just incase.
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Unread 03-10-2008, 08:56 AM   #15
LeftoverSalmon
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Had the same issue. It started as a light tapping only when it was cold out. Over a couple months the knocking got to the point it was sorta unbearable. Originally thought it was problably a lifter but turns out the bottom portion of one of the pistons had blown apart - found several large chunks of it in the oil pan. Im guessing that kinda threw things out of balance...

I bought a crate motor.... good opportunity to drop a stroker in there

Last edited by LeftoverSalmon; 03-10-2008 at 09:33 AM..
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