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4.0 piston slap?

Dmboggs74

New Member
Supporting Member
Joined
Dec 10, 2020
Messages
9
Location
Escondido..SoCal
Just changed the oil last week in my 02 Tj with 163k on the motor.
No issue right after the oil change. Sat for a few days and I started it up and pretty sure I got piston slap for about 10 seconds. Then it went away.
This morning. Same thing...for about 5 seconds.
I used 10w40 castrol high mileage syn blend for this change as I got it on sale pretty damn cheap. Usually use 10w30 high mileage whatever is on-sale.
Can the oil weight change cause this issue?
It's only at cold start up and goes away quick.
 

Paul Land

TJ Enthusiast
Joined
Oct 3, 2018
Messages
311
Location
New Jersey
Just changed the oil last week in my 02 Tj with 163k on the motor.
No issue right after the oil change. Sat for a few days and I started it up and pretty sure I got piston slap for about 10 seconds. Then it went away.
This morning. Same thing...for about 5 seconds.
I used 10w40 castrol high mileage syn blend for this change as I got it on sale pretty damn cheap. Usually use 10w30 high mileage whatever is on-sale.
Can the oil weight change cause this issue?
It's only at cold start up and goes away quick.
If your going to keep jeep, read my Holy-Moly post, don't let it take you 1/3 of a year, like what happened me to find rebuild. Titan Engines Ocala FL has 4.0L 1 week wait time. Call John and save a couple of $100s vs ordering on his Titan Engines web sight.
 

Rygrego

Member
Joined
Sep 30, 2020
Messages
29
Location
Mission Viejo, Ca
Just changed the oil last week in my 02 Tj with 163k on the motor.
No issue right after the oil change. Sat for a few days and I started it up and pretty sure I got piston slap for about 10 seconds. Then it went away.
This morning. Same thing...for about 5 seconds.
I used 10w40 castrol high mileage syn blend for this change as I got it on sale pretty damn cheap. Usually use 10w30 high mileage whatever is on-sale.
Can the oil weight change cause this issue?
It's only at cold start up and goes away quick.

No, the new oil grade will not cause this. It probably isn't piston slap but your lifters pumping up.
 

ColoJeep

Just a car guy
Supporting Member
Joined
Jan 30, 2021
Messages
927
Location
Elev.9052'
Piston slap typically lasts until the engine warms up. If the noise you hear lasts only 10 seconds it doesn't seem to be piston slap.
For what it's worth , I have driven high mile small block Chevys with actual piston slap for many years and 10's of thousands of miles without issue.
If the engine rattles revving up and then again rattles dropping rpm , watch out , that's likely a rod bearing ready to sign out.
 

Krusty_tub

Member
Joined
Apr 23, 2022
Messages
92
Location
Ct
5 seconds of start up rattle indicate oil pressure reaching the problem and quieting it down. Perhaps it was always there, did you put a different filter on
 

Paul Land

TJ Enthusiast
Joined
Oct 3, 2018
Messages
311
Location
New Jersey
I'm going to have to disagree that the oil caused your problem. These engines are dinosaurs and can handle just about any lubricant you put in them. If anything 20w-50 would quiet piston slap.
It did for 1700Mi, then quieted it permanently. But I'm lovin my new engine, no more tappy-tap-tap
 

williambmac

TJ Expert
Supporting Member
Joined
May 5, 2019
Messages
3,715
Location
Fucktard state of NJ
That isn't piston slap. That is a cracked and then later broken piston skirt. Big difference.

My 2000 WJ with a 4.0 started making noise at 100k miles. I dropped the pan and found pieces of #3 piston lying in the pan.
I drove it for another 182k miles in that condition and tried to blow it up numerous times. I sold it to the scrap guy at work, he drove it for another 2 years before the original transmission let go.
 
  • Wow
Reactions: ColoJeep

Paul Land

TJ Enthusiast
Joined
Oct 3, 2018
Messages
311
Location
New Jersey
That isn't piston slap. That is a cracked and then later broken piston skirt. Big difference.

Well, The Piston Slap Diagnosis came from 40 year performance/racing engine builder. Me's thinks he would know. But he did not crack open engine, so who knows.