Opinions on engine "knock" before i throw in the towel

[SicNastyXJ]

Ok so here's the story, just finished reassembling the 4.0 in my 2001 4wd auto. Complete rebuild except for crank, rods and pushrods. Motor has run fine and i have put just a little over 400 miles on it for break in purposes. After dropping in the motor i used a fram oil filter and 10w30 dino oil with lucas zinc additive to help with the break in but here is my problem.

Friday night it has developed what seemed to be a knock which gradually got worse until i made it to my destination. A few hours later i got back in and it did not make the noise any longer. Saturday after it warmed up the noise came back and got very loud but we still made it home. Family members are telling me it's a rod but i have one friend telling me that it's probably the oil needs to be changed to get all the crud out from break in.

Any thoughts?? I'm almost considering a reman engine at this point as i don't want to get rid of my rig.

 

[my2monkeys]

So you had the crank machined and all new bearings and pistons,cam,head machined with new valves ect.?

Did you put it together yourself, checking all the bearing tolerances and the like?

 

[old_man]

Get rid of the Fram Filter. I've seen way too many failures with the Fram.

 

[kastein]

Check your torque converter to flywheel bolts. If they are loose it will sound like a really mean rod knock.

 

[SicNastyXJ]

So you had the crank machined and all new bearings and pistons,cam,head machined with new valves ect.?

Did you put it together yourself, checking all the bearing tolerances and the like?

Yes.

Get rid of the Fram Filter. I've seen way too many failures with the Fram.

Interesting, i've ran fram filters on my Tacoma since i bought it new in 01. i'm considering either a Mopar or K&N though.

Check your torque converter to flywheel bolts. If they are loose it will sound like a really mean rod knock.

I may have to look into that before i come to conclusions that the motor is toast.

 

[garr]

This may be too simple, are you sure it is an engine knock & not just the noise from the Evap Purge/ Vent Solenoid ? (located on the passenger side of the firewall)
I have had more than one person tell me their XJs engine was knocking when it was Just the solenoid doing it's thing.

 

[cruiser54]

Fram filters have crappy anti-drainback valves for one thing. The way our oil filters are mounted make it critical to have a good quality oil filter. Napa Gold, Wix, or Mopar is the way to go. Old_Man is correct. we have seen knocks go away by ditching the Fram for a quality oil filter. For $6 it's worth a try, isn't it?

 

[1987Comanche]

Bad lifter?? My '87 2.5 MJ did the same thing and that's what I traced it back to. It was weird but an easy fix on the 2.5. 4.0 will require pulling the head though...

 

[tugalo]

loose flexplate bolts or cracked flexplate?