Hey guys, i have a 93 xj w/ 185k it runs great but there is a knock in my motor. The best i can describe it is, not really a tick or a knock it kinda in between and i can say that ive heard this noise in many 4.o 's. Its not a clacking rocker arm its further down in the head and sounds like its close to the oil fill area. I dont think its a wrist pin because the noise does not speed up with engine rpm, as a matter of fact it goes away just above idle and thrugh the entire rpm range. I bought the truck from a friend who drove it everyday with no issues so im not that worried about driveability, like i said it runs awesome, but the noise is driving me nuts! I really dont like my truck sounding like a diesel, i know lots of you probably had or have this noise, so what did ya do? Thanks!

 

Same thing I'm dealing with lol my xj drives fine but idk what it is either

 

#5 Defiance665
CF Veteran



Join Date: May 2009
Location: Michigan, 48657
Posts: 3,683

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1989 Cherokee Year: 1989
Model: Cherokee
Engine: Renix 4.0
Transmission: AW4
Transfer Case: NP231
Front Axle: Dana 30 Vaccum Disconnect
Rear Axle: Dana 35
Tires: 235/75/15
Lift Specifications: 4" rear, 3" front
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does it sound like this?
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IT SUCKS DON'T IT? I'VE ALREADY RULED OUT A ROD KNOCK, BUT IVE HEARD OF PISTON SLAP, WRISTPIN NOISE AND LIFTERS. MY ROCKERS ARE TIGHT AND DONT CLACK SO IDK....... THERES A VIDEO OF A GUY W/ A RED JEEP ON HERE MAKING THE SAME NOISE BUT I DONT KNOW HOW TO ATTACH THE VID, IF YOU SEARCH ENGINE KNOCK YOU'LL FIND HIM ITS ON THE SECOND PAGE I BELIEVE. I SENT HIM A PM HOPEFULLY HE WILL RESPOND. I'LL KEEP U POSTED.....................

 

Does it go away once it warms up? May just be some piston slap.

 

Mine knocks, sounds like a bottom end knock but only does it at like 3,000 rpms- 3,500 and at cold start up. I'm just running it till she blows, then replacing the motor.

 

Fixed...

Mine comes from the top end, its always there but gets quieter when its at op temp. Pretty sure its cam/lifters. Just gonna run it till it blows (IF it blows) Ive beat the hell out of it and nothing has happened so far. It hasnt gotten any louder.

 

trs80, its there no matter what the temp but its only at idle, any rpm above that it goes away. i pulled the valve cover and i have oil coming out of all the rockers, it sounds just like DEFIANCE'S video ( thanks D btw ). i'm not really worried about the motor blowing; i dont think it will, i just want to quiet this thing a bit. i actually thought of just kicking the idle up a bit since that is when the noise goes away. aaahhh i d k this noise is aggravating and embarrasing it sounds like a pos but it runs awesome.........

 

knoxville,

To me it sounds like you have some valve train noise. The lifters tend to be 'loud' at idle due to lower oil pressure/flow. Nothing to loose any sleep over.

I have had good luck by running Seafoam through the crack case (right before an oil change). I add some Marvel Mystery Oil to the fresh oil mix and have heard quite the improvement in idle quality. I too am a stickler for how my Xj runs/sounds. Hope this helps.

 

I had a cracked piston that did that, at idle it sounded like a 5yr old with 5# hammer, at 1500 it would go away and sounded like any other 4.0.

 

TRS, What brand/weight oil are you using? i cant go too heavy here in Chicago the last few winters have been Brutal................... oh btw i just put seafoam in, i just gotta put some miles on, how many do you think? a hundred or so?

 

A hundred would be plenty.

I run Amsoil 5w30 with about half qt of MMO and a Mopar Filter. I run the 5w all year, as I have tried 10w and it made the lifters louder.

 

ok thank you, i'l try that. not synthetic tho right?

 

Amsoil is full Syn. I too have 185k on the odom and have had no ill effects from running full syn in engine. Its up to you, Castrol syn blend is another good option if you want to stay away from a full syn. The only problem I see going full syn is that any leaks may become worse as the syn will 'slip' by the seals at a faster rate.

 

Ok, thanks alot i have a few more miles to go with the seafoam in my oil and i also threw some MMO in the gas just because.I'll reply with results after my 5W30 oil change with MMO; hopefully it works! Thanks again guys

 

Mine ticks when engine shuts off weither running for ten seconds or a half an hour any ideas what that might be