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  #1  
Old November 12th, 2017, 16:12
asymptonic asymptonic is offline
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Piston slap: how long?

Okay, so what I thought was lifter tick clearly isn't. MMO spraydown did nothing, and on a long drive today I'm noticing the slap doesn't quiet down after warmup any more, at least on one cylinder. Recent oil change w/ Rotella T6 5w40 and a new Wix 51515 filter didn't seem to help with startup clatter either, though I'm unsure whether it made the always-clattering cylinder start or get worse.

Question is: How long should I run like this? Should I be looking to get the engine rebuilt soon? 192k at this point.
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Old November 12th, 2017, 16:42
blakews2217 blakews2217 is offline
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Piston slap: how long?

What year / motor? The easy answer is not at all until you get it rebuilt. But as for my meaningless opinion are you sure itís piston slap? Either Iíve been away too long and gotten too lucky to have a 365k 4.0 Jeep going with more lifter tick than I thought it could make or Iím a dummy. Either way I have early heard of what some perceive to be piston slap actually be piston slap. If it is then it should be hurting valves and piston faces along with leaving a funny pattern in the crank/ rod bearings.


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Old November 12th, 2017, 20:27
asymptonic asymptonic is offline
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Re: Piston slap: how long?

Motor was in the signature, '98 4.0. If not piston slap, what would rattle heated up? Plenty noticeable at idle, and through maybe 1200rpm. Above that not sure if its going away or just inaudible above engine noise.

To clarify, its a consistent single clack per fire on whatever cylinder is doing it. A lot of clatter cold but only one once warmed up.
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Old November 13th, 2017, 15:57
blakews2217 blakews2217 is offline
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Piston slap: how long?

Quote:
Originally Posted by asymptonic View Post
Motor was in the signature, '98 4.0. If not piston slap, what would rattle heated up? Plenty noticeable at idle, and through maybe 1200rpm. Above that not sure if its going away or just inaudible above engine noise.

To clarify, its a consistent single clack per fire on whatever cylinder is doing it. A lot of clatter cold but only one once warmed up.


Sorry. Iím using Tapatalk so I donít see signatures but I wish I did. As for the rattle where about the motor does it sound like itís coming from? Front? Back? Top? Bottom? Does it sound more like a knock? If itís at the exact time every fire Iíd be more curious about a bent push rod. If you can pull the plugs and shine a light down in the hole and look at the top of the Pistons. If you canít see one use a ratchet and socket to turn the motor. If you donít see whiteness marks from the valves touching then Iíd almost rule out piston slap. What tells you itís worn? Low compression?


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Old November 13th, 2017, 18:25
asymptonic asymptonic is offline
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Re: Piston slap: how long?

Quote:

Sorry. Iím using Tapatalk so I donít see signatures but I wish I did. As for the rattle where about the motor does it sound like itís coming from? Front? Back? Top? Bottom? Does it sound more like a knock? If itís at the exact time every fire Iíd be more curious about a bent push rod. If you can pull the plugs and shine a light down in the hole and look at the top of the Pistons. If you canít see one use a ratchet and socket to turn the motor. If you donít see whiteness marks from the valves touching then Iíd almost rule out piston slap. What tells you itís worn? Low compression?
Definitely a clack/clatter not a knock. Seems to be louder on the bottom, maybe. Sound is somewhere between cyl 3 and 5. It does seem to be the same time each fire but random loudness. I'll try to get a look when I have some free time, which is rare.

Several cylinders rattle at cold start, but it quiets down to just the one when hot.

No compression test yet, just trying to narrow down this increasingly loud clatter.
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Old November 13th, 2017, 19:55
blakews2217 blakews2217 is offline
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Piston slap: how long?

Quote:
Originally Posted by asymptonic View Post
Definitely a clack/clatter not a knock. Seems to be louder on the bottom, maybe. Sound is somewhere between cyl 3 and 5. It does seem to be the same time each fire but random loudness. I'll try to get a look when I have some free time, which is rare.

Several cylinders rattle at cold start, but it quiets down to just the one when hot.

No compression test yet, just trying to narrow down this increasingly loud clatter.


I know the feeling. Iím chasing DW down with seemingly no end. If looking in the spark plug holes shows no answers Iíd suspect a lifter/ pushrod/ flattened lobe. Probably a ticky lifter. Can you get a vid? Iíve had my dads jeep run from 155k to 375 k with lots of lifter clatter. Sounded like a diesel at the end. Then someone ran it down in it off street parking and totaled it. But it still fired right up to drive away to the scrap yard.


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Old November 14th, 2017, 08:46
asymptonic asymptonic is offline
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Re: Piston slap: how long?

Yeah, I'll grab a video of the sound this afternoon.
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Old November 14th, 2017, 15:13
asymptonic asymptonic is offline
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Re: Piston slap: how long?

Okay, here is a video of it. Not that helpful I think. The noise isn't as pronounced as this video makes it seem, I think the camera was too close to the engine. It does seem like the noise goes away at high enough RPM however.

https://youtu.be/3JKNCib2-Rk?t=48

Watched some videos of other Jeeps w/ lifter tick, and this one has a very similar noise which he attributed to the lifters:

https://youtu.be/29I5fNAv-8M?t=77
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Old November 14th, 2017, 15:54
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Re: Piston slap: how long?

Are you the original owner of the jeep? Luckily for us jeepers the 4.0 is damn tough. Just keep changing the oil and drive on. If you can afford to do a full tear down and rebuild do it. If it makes you feel better my grand cherokee 4.0 makes awful noise lifter/piston related. That was over 30,000 miles ago. Just keep changing the oil. Engine runs like normal besides the noise.

Like I said if you have money then tear it down and do a full rebuild. In my experience, at this point nothing in a bottle you can pour in the case is going to make that noise go away.
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Old November 14th, 2017, 16:15
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Re: Piston slap: how long?

First off lets verify what cylinder(s)

Pull one spark plug at a time and listen to the noise. It should either get worse or better on the offending cylinder(s).

Personally I would never run 5w anything in a 4.0L. Since your option is a rebuild, I would do a change to 15w40 Rotella and see if it quiets down. It is cheap diagnostic step. Don't bother changing the filter.
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Old November 14th, 2017, 16:55
asymptonic asymptonic is offline
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Re: Piston slap: how long?

Quote:
Originally Posted by themauler View Post
Are you the original owner of the jeep? Luckily for us jeepers the 4.0 is damn tough. Just keep changing the oil and drive on. If you can afford to do a full tear down and rebuild do it. If it makes you feel better my grand cherokee 4.0 makes awful noise lifter/piston related. That was over 30,000 miles ago. Just keep changing the oil. Engine runs like normal besides the noise.

Like I said if you have money then tear it down and do a full rebuild. In my experience, at this point nothing in a bottle you can pour in the case is going to make that noise go away.
Yeah, I'm it for the owner, so its never seen maintenance abuse at least. I probably can afford the teardown, but I have some road trips coming up that are in the way. If she won't die on those I'll might take care of it after the holidays.
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Old November 14th, 2017, 16:56
asymptonic asymptonic is offline
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Re: Piston slap: how long?

Quote:
Originally Posted by old_man View Post
First off lets verify what cylinder(s)

Pull one spark plug at a time and listen to the noise. It should either get worse or better on the offending cylinder(s).

Personally I would never run 5w anything in a 4.0L. Since your option is a rebuild, I would do a change to 15w40 Rotella and see if it quiets down. It is cheap diagnostic step. Don't bother changing the filter.
Interesting, I would have expected thinner oil at start would improve startup lubrication. Too thin at cold temps?

Also, pull the spark boot while the engine's running one cylinder at a time?
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Old November 16th, 2017, 14:44
Rockwood Rockwood is offline
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Re: Piston slap: how long?

Every damned 4.0L I've heard has that same noise, to some extent. Sounds like an older Mercedes diesel. The valvetrain on these motors isn't the quietest...

As long as it's not coming from the front end (chain issue) or the bottom (rod knock), I'd leave it be.
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Old November 16th, 2017, 18:03
RCP Phx RCP Phx is offline
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Re: Piston slap: how long?

A lot of the so-called lifter tick is caused by the fact that it is a non-adjustable valve train. I seen horrible rocker arm/pivot wear that no ever does anything about it! My stroker is a quiet as a "church mouse"!
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Old November 16th, 2017, 20:49
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Re: Piston slap: how long?

Quote:
Originally Posted by asymptonic View Post
Interesting, I would have expected thinner oil at start would improve startup lubrication. Too thin at cold temps?
You know, I am wondering about that too. I have on occasion considered switching my '92 over to the same diesel-rated 5w40 full synthetic I use in my VW TDI, would have thought the same thing as asymptonic - with slightly thinner at startup it would help with cold startup wear. Of course, I immediately follow that thought with "it's gone 255K miles on non-synth and seems to be running solid/strong, why mess with success?" so I've not actually gone beyond an occasional random notion.

Old_Man, would you care to expand a little on why you don't like the idea of 5wXX in the 4.0?
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