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Decisions. 1992 knocking.

S

SanDiegoOverland

NAXJA Forum User
Location
San Diego
1992 xj laredo auto, np231 d30/d35

all stock

My truck recently started knocking, here's the rundown:

-good oil pressure
-slight blowby
-1 quart down after a month or two (I have a good rear main seal leak, tho)
-good power
-no other symptoms.


-Checked flexplate bolts, all tight, but locktited and re-torqued anyways. didn't change the sound.
-Engine oil is topped off, and not allowed to get low.

Here's what I'm thinking:

1. My truck was running cool for several months, due to a bad thermostat and a nice alum radiator. this probably meant lots of extra fuel dumped into the system...any direct correlation to a knocking (not tapping) noise?

2. Should I run this engine into the ground no matter what? or should I be looking around for a new motor?

3. Would any of you others, with a tight budget using your jeeps as daily drivers/sole vehicles see this a reason to sell and start over? I honestly don't have $300-500.00 to pay for a used motor, let alone a couple thousand to pay for a rebuild if that's what's required. I'd rather sell my rig for a fair price to someone who could take care of the problem if it ever became a real issue.

If I kept it, I'd honestly probably not do anthing extra for it, other than drive it gently like I have from the get-go. It might end up running for a really long time with whatever issue/non-issue it has.

I've read through lots of knocking threads where a cracked flexplate or bolts have been the trouble, but I honestly don't have time to pull the tranny to check the flexplate, nor do I have the funds to have someone do it. Thanks in advance for any insight.

Oh, and I have lots of tools and knowhow short of a full rebuild, and I do all my own work, so feel free to send me that way, if you know of a process that might help.

-Brian
 
I am in almost the same boat as you motor wise. I havn't done the flexplate yet. What I have found so far is pick a part around here charges about $125 for a motor. Cheap enough if I can find one with decent miles and a squished top. You didnt mention your miles, but from looking around 220k plus is not unusual. Since your wifes likes it...
 
yeah, sorry...about 175k.

and she does like it! :)

I'm trying to wrap my head around the idea that a dead motor doesn't mean its not a good car, and even when it goes, it might be a long time from now.
 
just because the flexplate bolts are tight doesn't mean the plate itself isnt cracked. I would still put my money on the flexplate being cracked, especially since you say that you haven't noticed any loss of power. set up a work party, get a few people over there, and you can get the tranny out and back in within a few hours. a new flex plate, some beer/soda and some pizzas/burgers is going to be cheaper than any other option :D
 
Shortly after I got my 88 it started what sounded like a rod knock. Turned out a bad bearing in the alternator. Just take the belt off and see if it still makes the noise.

If it's a rod/main bearing as long as it hasn't damaged anything you could just put new bearings in it.
 
MJR said:
Shortly after I got my 88 it started what sounded like a rod knock. Turned out a bad bearing in the alternator. Just take the belt off and see if it still makes the noise.

If it's a rod/main bearing as long as it hasn't damaged anything you could just put new bearings in it.
Click to expand...


used a stethescope to listen while it was running last night. While it was knocking I heard nothing from rocker area, nothing from the exhuast manifold, nothing from the intake manifold, so grudgingly I got under the car and carefully probed.

the tranny pan was making zero noise. The bellhousing, though, was noisy as all get-out, and in 2nd place was the oil pan on the sides, but not the bottom.

So maybe it would be to my benefit to pull of the tranny inspection plate again and see if I can get a look at a crack. I've heard of some using a long screwdriver and possibly a mirror, though, from experience, I know that its very tight in there.

-B

p.s. came out to a coolant leak this morning. sure hope its a hose that I pulled off to replace my -stat and not the pass side rad.tank. :tear: jeez.
 
When it rains it pours, eh?

X2 on have a work party, buy food/beer/stuff. Even if you need to buy all the tools it won't cost you that much all things considered - I got my 3 ton hydro jack at harbor freight for $70 and it's stood up to me dragging it around multiple junkyards, you probably have all/most of the wrenches you'll need except maybe the E12 (external torx) bit for the top 3 bellhousing bolts. Stock up on pb-blaster, get a propane torch if you don't already have one (it's like ten bucks at home depot and good enough for the crossmember bolts/studs), and go at it.

A whole new tranny costs $120 at the pull-a-part here, so I can't see a flex plate costing more than like 20-30 bucks. Make sure you get it from a compatible year, or preferably exactly the same year, and I think the transmission type might matter too but I'm not sure.
 
MJR said:
Shortly after I got my 88 it started what sounded like a rod knock. Turned out a bad bearing in the alternator. Just take the belt off and see if it still makes the noise.

If it's a rod/main bearing as long as it hasn't damaged anything you could just put new bearings in it.
Click to expand...


both good points. :star:
 
Swapped in a new upper coolant hose and bought a tiny mirror, to see if I can get a look @ the flexplate with the tranny installed.

Hopefully that fixed my coolant leak problem. In any case, the old hose is now a spare, and really needed to be swapped anyways. (lower is new)

I'll post up if I find anything. Good thing is I cleaned up my inspection cover and left the bolts fairly snug, but not torqued to like 100ft-lbs like they were when I first had to remove them. hahaha!
 
Do you have any video of the noise? That would help quite a bit as well. Could be piston slap. I've heard it be pretty loud on some of my previous xj's. Every 4.0 I've owned sounds like a little diesel.
 
mrtosh said:
Do you have any video of the noise? That would help quite a bit as well. Could be piston slap. I've heard it be pretty loud on some of my previous xj's. Every 4.0 I've owned sounds like a little diesel.
Click to expand...

http://s210.photobucket.com/albums/bb64/kodiak1232003/?action=view&current=IMGP7397.flv

here's the video. just walked outside on my lunchbreak. I tried to get the noise from a few different spots.

Engine always runs well, lots of power, oil pressure at about 40psi give or take 5psi up or down...

weird.
 
I have been having same type problem lately, and finally got around to crawling under it today. I found my starter to be not even finger tight. I could wiggle it around considerably. That got rid of most of it, I still need to check the flexplate. Did the cleaning today maybe tommorrow if its pretty. My vote from the video is flexplate, or a loose alt, steer pump, or some such bracket type thing. It don't sound like motor to me.
 
SanDiegoOverland said:
http://s210.photobucket.com/albums/bb64/kodiak1232003/?action=view&current=IMGP7397.flv

here's the video. just walked outside on my lunchbreak. I tried to get the noise from a few different spots.

Engine always runs well, lots of power, oil pressure at about 40psi give or take 5psi up or down...

weird.
Click to expand...
Welcome to the wonderful world of piston slap my friend. Sounds like every other XJ I've owned. I've heard it alot worse actually. On my '99 motor w/only 65k on it sounds pretty much the same if not a bit louder but clears up above about 1200 R's. Drive it like you stole it!
 
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