bearing(?) noise & rebuild question

hey all,

I love my '95 Cherokee (4WD, 4.0L inline 6 cyl) and I even learned to love the "knock, rattle and roll" that the 4.0L engines are infamous for. But after a recent oil change (I used castrol 10-40W) my wife went on a quick trip to visit family (~5 hours each way), and the truck developed a new noise to accompany the standard knock. It's more of a loud tapping (not a ticking).

I got under the jeep and the loud tapping definitely sounds like it's coming from the oil pan. Damn! Well, I'm considering a half-rebuild (just the bottom end). Are there some tests I should run before tearing into her? Also, can I change the rod AND main bearings without removing the engine? I would like to just jack it up, drop the oil pan and do the work right there. Will I be able to check the crank tolerances with the shaft still in the engine?

Any help is appreciated.
Take care,
blakelock

bought a 97 4.0 2WD, 157000 miles, 6 months ago for my son. had him do the oil changes and use mobil1 for quality and cost savings.

noticed recently that it's making a kind of 'diesel' rattling sounds that sounds like it's coming from the front end/lower end (similar to yours) area of the engine

am changing water pump, but the old one doesn't really seem that bad

have also notice oil pressure drop during highway crusing

do you think problem is oil pump, bearings, crank related instead?


yikes$$$$$$$$$

I feel your pain$$$$$$$

:eek7:

I hear ya. Actually, I had been dreading major engine problems (because of the "standard" 4.0L engine knocking) when my water pump started making a ton of noise. My first thought was "well, I guess this is it for the engine", but it turned out to just be the water pump. I was lucky for the time being.

Previously it had been making the diesely noise, especially when I give a quick short jerk to the throttle cable. I'm not sure if that's bearing or what but now I've got this new noise. After the engine warms up the noise is nearly constant (idling, accellerating, constant speed, ...). A loud tapping from the bottom of the pan now haunts me in my sleep.

help!

-blakelock

ya- you can do the bearings with the engine in the vehicle. Been there - done that - not a pretty sight but it's possible.

you can check the clearances with plastigauge but you won't know rod out of round or journal out of round. that needs special tools and more teardown out of the vehicle.

You will see the wear pattern in the bearing though.

how many miles on the engine???

JD

I bought the jeep ~1 year ago with 130K miles. Now it has just passed 150K! My wife and I drove accross the country and it performed perfectly. Luckily, it waited 'till we found a home before giving up.

So, when I change the main bearings, do I just remove the main cap then try to tap or slide the top half of the bearing out from around the crank? Any hints on this.

Also, can I replace the all the main bearings this way? I'm concerned that either the front or rear most bearings might be more difficult to remove with the engine still in the car.

One more question. In my "in depth" Haynes manual, it states that the bearing are color coded. I guess that means I have to open up the pan before I know what replacement bearings to get. Is this correct?

thanks,
blakelock

to do the rod bearings, remove the cap nuts and tap on the cap to remove it. Get a pair of rod bolt covers and put over the bolts BEFORE you try and remove the upper rod bearing shell.

do this on each rod.

use assembly lube when you do the final assembly after checking bearing clearances.

for the main bearings - loosen all the main bolts and take out one set of bolts at a time. let the crankshaft hang down a few thousandths of an inch so the upper bearings will release easier.

use a rivet or something in the oil hole to push the upper main shell out of the block towards the bearing tang and roll the new bearing in the opposite way.

If the bearings are worn you will see brass in thecenter of the bearing. the wear marks should be centered on all the shells.

Plastigauging involves multiple assembley for each bearing. this is not a quick job or an easy one especially working over the crossmember.

JD

howdy.
Here's an update. I did it!!! I'll give you the description of my bottom end rebuild.

I first tried to use a couple of tricks I read about to verify it was a bottom end/rod knock I was hearing. I hooked up a timing light and saw that the tapping was occurring at double the frequency of the timing light. This means the noise is in the bottom end as apposed to the top end. I then shorted out each spark plug wire with a continuity tester (test light) to find which rod was making the noise but I couldn't really tell. So let's go for it!

- Jacked it up and supported it on jack stands.
- drained oil, replaced filter.
- Disconnected battery and removed starter.
- Removed bell hoousing observation plate (Found several loose flex plate bolts! so I administered lock tite and tightened them back up).
- I did not remove the steering dampner or disconnect the shocks to lower the cross memeber (as suggested in the Haynes manual). That would have provided more room but the front wheels were already resting on the ground and I could not jack up the car any higher. I did not proove to be much of a problem though.
- Remove the oil pan. It was a tight squeeze getting the pan out (probably would've been easier with the cross member dropped) but I managed. In the pan I found quite a bit of black crusty particles (maybe burnt oil?) and one chunk of metal (about the size of half a chocolate chip). I have no idea where the metal came from (maybe the top end???). I cleaned the pan out and went back to the bearings.
- Removed oil pump.
- I started with the rod bearings. The old rod bearings were worked pretty badly. 2 or 3 were worn to the copper. Actually the copper was usually visible on the outer side of the bearing, not the inner. So I replaced them with new standard-sized bearings, geased them up with assembly lube, and plastigaged each one after assembly (tourqued to 33 ft-lbs). After bearing replacement, they were all perfectly within spec (.001-.003 in)! YEAH!
- Then I moved on to the main bearings. I checked #! and #7 with plastigage (tourqued to 80 ft-lbs). They both looked very good, showed very little wear at all, and were within spec (.001-.0025 in) according to plastigaging so I did not replace the mains. (Also, it was beginning to rain and I was working outside so I did a quick risk/benefits analysis and figured since the mains were within spec, it wasn't worth risking getting water in the bottom end).
- I transfered the pick-up tube and screen to the new oil pump, primed the pump with oil and installed the new pump.
- Then, I put a thin coating of RTV sealant on the pan edge and the engine block, placed the gasket on the pan and lid it into place. Again, it was a tight fit but eventually it went. Then I tightened the pan bolts after making sure the gasket was still in the proper place.
- Reinstall the starter, bell-housing observation plate, fill with oil, and reconnect the battery.
- Started her up and it was smooth and purring perfectly (except for the standard exhaust leak putter from the cracked maniflod). :(

I was exstatic and considering it took me ~6 hours, it's no wonder! So it seems perfect so far but I guess I'll need a couple hundred (or thousand) miles to really be able to say that. I'm not really sure what the recommended treatment of new bearings is but I suppose I'll do frequent oil changes (~every 500 miles) for a bit then ease into standard oil change intervals.

If there are any other suggestions for post-bearing replacement care or any questions on how I did this job, please post!!

thanks for all the advice,
blakelock