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Piston slap or lifter tick?

asymptonic

NAXJA Member
NAXJA Member
Location
Austin, Texas
'98 XJ, AX15. Only when cold, diesel-like clatter only at idle that disappears only when the engine warms up. High RPM its not audible but revving it also doesn't clear up the noise when it returns to idle. I've been messing around with oil types and thicknesses to address a slightly low (13psi) hot idle so that's been variable.

So which is it, most likely, and what do I try to eliminate it? Oil wise I'm currently running a non-synthetic 10w30, but with a quart of Lucas Oil in it to help the oil pressure. Likely to try a 5w40 next.
 
When cold, does the noise get louder as RPMs increase when you rev in neutral?

I have the "diesel-like" lifter clatter, and the noise does not get louder as the motor is revved. In fact, by about 1500 rpm, it can barely be heard. My experience with piston slap is that it will get louder as the motor is revved. Piston slap is more of a "knock" sound than the lifters make, which some people call a tick but to me is more of a "clatter" in the 4.0, as you stated.

Mine improves if I drive with higher revs more often. It is worst when I restart the engine after sitting for a while after a hot shutdown. My theory is this is because the hotter, thinner oil drains more easily out of the HLAs and collapses them. I haven't had much success in using different oils or additives to reduce the noise. I just live with it, and it runs great regardless.
 
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When cold, does the noise get louder as RPMs increase when you rev in neutral?
No, just disappears.

I have the "diesel-like" lifter clatter, and the noise does not get louder as the motor is revved. In fact, by about 1500 rpm, it can barely be heard. My experience with piston slap is that it will get louder as the motor is revved. Piston slap is more of a "knock" sound than the lifters make, which some people call a tick but to me is more of a "clatter", as you stated.

Mine improves if I drive with higher revs more often. It is worst when I restart the engine after sitting for a while after a hot shutdown. My theory is this is because the hotter, thinner oil drains more easily out of the HLAs and collapses them. I haven't had much success in using different oils or additives to reduce the noise. I just live with it, and it runs great regardless.

Hmm, I don't think I've noticed it happen at all on a hot engine after shutdown, but it's something I should try. How long are you letting it sit before restarting?
 
No, just disappears.

That sounds like lifters/hydraulic lash adjusters--not piston slap. When I start mine, it always sounds very smooth until it settles down to a low idle, then the clatter builds slowly. It's intermittent, so it's tricky to nail down when it's best/worst but it definitely seems to be quieter after I've given it some higher-RPM workouts. Floor it and run it up to the upper RPM range under load, and it's quiet afterwards. It's also quieter after a run on the freeway than it is if I've been slogging around town at low RPM for a while. Mine definitely seems to come and go more with variances in RPM than with heat while it's running. Possibly it's higher oil pressure helping pump them up, or just that the lifters are "loosening up" after more of a workout.

Hmm, I don't think I've noticed it happen at all on a hot engine after shutdown, but it's something I should try. How long are you letting it sit before restarting?

Maybe an hour? The engine is still good and warm, but has sat long enough for oil draindown. Again, as intermittent as mine is I could be wrong here, but that seems to be the case.
 
You have sticking lifters. Take the valve cover off, and use a spray bottle filled with MMO (Marvel Mystery Oil) to spray soak the entire valve train and lifter tops. Reinstall the valve cover. Let it sit over night before restarting.

You can also spray it some with PB Blaster when you use the MMO.

Worked like a charm on mine after 13 years of the same exact problem.
 
An easy way to pinpoint lifter issue is turn the engine off immediately when you hear the noise. Wait 10 seconds and restart.

And? I think you forgot the rest of the story? So, If it blows up on the restart, it was lifter tick? LOL., JK.
 
Maybe an hour? The engine is still good and warm, but has sat long enough for oil draindown. Again, as intermittent as mine is I could be wrong here, but that seems to be the case.

Quick update for posterity. Had a nice long drive followed by a 1 hour shutdown. Firing it up had the clatter back, but for just a few seconds. Definitely sounds like excessive draindown in the lifters based on that. Mike: Saw your thread about soaking the top end in MMO. Will do when I have a good reason to pull the VC. I have a slightly leaking CCV grommet so I'll probably tackle that with the VC off just because. Anything else I should look at/service while I have the cover off?
 
Did that yesterday. The noise happens on cold start easily, so I shut it down and restarted 10 seconds later. Noise still there. Not sure what that was meant to show though.
 
Well, I did Ecomike's MMO soak last night. Sadly no go. Still rattles on startup and then quiets down to a single tick at operating temperature. I'm currently running 10w30 w/ Lucas Oil stabilizer for a slightly low oil pressure when running hot on the highway. Could the thickness at cold start be an issue?
 
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