• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Need advice on rod/main bearing job

gone postal

NAXJA Forum User
My 167k old '91 has a knock and low pressure. I haven't pulled the pan yet, but I'm sure that it's in need of a bearing job. I have done some searching on here, but have a few questions.

Are there any special tools that I'll need for this? I have basic hand tools and I'm not afraid to dive into projects, but this is going to become my daily driver, so I'd like to get it into better shape than it is, but don't want to risk blowing it up. I figure my options from here are to either drive it till it dies, do this job or buy a Jasper engine for $3k. I'd rather try this to at least buy some time.

I searched on AutoZone and crank bearings are $67 and rods would be $35, so roughly $100. I don't know what condition my crank is in, but it does have 167k on it, so I think I'm probably better off going all new considering that a crank kit is $180 after core refund (http://www.autozone.com/servlet/UiBroker?UseCase=C001&UserAction=performMoreDetail&Parameters=TRUE%7C%7ECrankshaft+Kit+Remanufactured%7C%7E%2450.00%7C%7ERECON%7C%7ENONE%7C%7EFALSE%7C%7EFALSE%7C%7E480961%7C%7E1223%7C%7E22406%7C%7EReground+and+micro-polished%2C++++++++++++++++++++++++++%0Aparkerized+coating+applied+for+break-in+++++++++++++++%0Aand+durability.+++++++++++++++++++++++++++++++++++++++%0AOil+seal+speedi-sleeves+installed+for+new+sealing+++++%0Asurfaces+and+packaged+with+matched+Premium++++++++++++%0Arod+bearings+and+main+bearing+set.++++++++++++++++++++%0AWarranty+for+commercial+applications+is+3+months.+++++%0ACall+1-800-817-3266+for+warranty+claims%2C+application++%0Averification%2C+and+estimated+delivery+times.%7C%7E%24230.99%7C%7EJeep%7C%7ECherokee+4WD%7C%7E1991%7C%7E3+MO%7C%7E65.0%7C%7ENONE%7C%7EV)
and that includes crank, rod & main bearings. Add another $70 for an oil pump and a few bucks for oil pan gasket and I'd be set right? Should I do anything else while I'm in there? I don't think my rear main is leaking, but for the $14 would it be worth doing?

Also, with a 3" lift and 31's, what is the chance I'll be able to do this w/out a bunch of hassle? Would I need to remove tires and drop the axle? On a scale of 1-10, how hard would this job rate?
 
Well, considering that you will either have to:

- Pull the engine out of the Jeep or,

- Pull the transmission off so you can pull the crank out the bottom of the block,

A $14 rear main seal sounds kinda trivial? I mean, all that trouble and you would not change the seal? The new crankshaft has to fit inside a seal that has 167k miles onit. I doubt it will ever seal again.


Anyway, thats a lot of work just to do nothing but a new crank and bearings. If the oil pressure has truly been low you probably also have damaged the camshaft and possibly the lifters as well.

So, if the engine gets a crank and bearings, then it should get totally refreshed or you may just waste your money.

I would consider swapping in a lower mileage used engine over just a crank and bearing replacement.

By the way, what are you calling "low" for oil pressure? It might not be a knock. It may be an exhaust leak or soemthing else.

My XJ has 233,654 miles on its original engine and it still doesnt knock and oil pressure remains at 20psi all the time after its warm. It only goes to 28 or 30psi when first cranked up and still cool. It does have blow by but it runs like a charm.
 
Pretty ambitious. Pull the engine. Just a bearing job in the frame sucks. You can't install a crank without removing the tranny. Pulling the engine will be "fun" compared to what you're considering. I would really consider the used motor route. There's alot of them out there.
 
Alright, I'm an idiot. I know that it's possible to replace the bearings w/ the crank in place (although a PITA), I didn't know that the tranny would have to be pulled to remove the crank, but it makes perfect sense - just didn't think it through. I just don't want to get in there to find the crank scarred up b/c new bearings would be a waste on a messed up crank and I'd be pissed to waste the time of getting in there just to seal it back up w/ shot bearings/crank.

Unfortuneately there are only 3 yards in town and I know for sure 1 of them doesn't have any 4.0s b/c I was there last week.
 
gone postal said:
...........Unfortuneately there are only 3 yards in town and I know for sure 1 of them doesn't have any 4.0s b/c I was there last week.
Keep saying to yourself http://car-part.com/ is my friend:cool:
 
You got to pull he eng. not only do you need to pull the tranny but you will also need to pull the radiator fan and shroud, so that you can get to the timing cover and timing chain(which is attached to the crank.............. pull it out and replace it or rebuild it with a stroker crank!



Flash
 
You sure the knock is a bearing problem. Could be a bad wrist pin, cracked pistion or even something simple like a cracked fly wheel. But on the same note I have to agree with the group if your gona go that far into it might as wheel do it all. If the crank is bad for about it's only about 3-500 more to do a stroker. That's why I now have a stoker. Was gona do rods and mains over the winter one year and found a burned up cam and crank. Got my remain head, rebuild kit, bored t-body, and new exhaust off E-bay for alot less than local parts stores was also the only place I found the 258 rods. Got a remain crank and my other parts from O'reilly's And got my ford injectors off a gent In my local jeep club. www.lonestarjeepclub.org
 
You don't just buy bearings, remove the old and install the new. After the crank is removed a machine shop should mic, regrind the journals and polish them if you're doing a real good jod. The rods wear somewhat elliptical and need to be rebuilt and the bearing arear made round again. The block is best align bored or kissed with the bearing caps installed so everything is straight and precise. After the above work is done some assembly is required to determine what size bearings are needed and where.

Anything other than the above is a band aid and a short lived quick fix.
 
If its and auto then checking the torque converter bolts is a good idea.

a loose TQ bolt can scare the crap out of ya..........it sounds alot like a rod knock!


Flash
 
What is your cold and hot oil pressure? Oil pressure at cruising speed?

What kind of noise is it making?

Does the noise increase, decrease, or go away after warm up.

The 4.0's are notorious for being noisy beasts. They are also known for making well over 300,000 miles while complaining all the way with scary sounding noises!

Yours is barely broken in!

I would make sure what the problem is, if it is a problem first!

Low oil pressure limit at hot idle according to Jeep is a dismal 13 psi! Low enough to scare the hell out of most of us, but apparently OK for 4.0's.
 
I've done plenty of engine rebuilds, and unless you have reason to believe you have crankshaft damage (i.e., you ran it out of oil, etc.), you may be FINE leaving your old crank in position and installing new rings, con rod and main bearings, as well as a rear main seal.

If the clearances in your oil pump are fine (they usually are since they are the best lubricated parts in your entire engine), you might consider retaining your old pump as well.

Drop the oil pan and pull your bearing caps and take a look at the crank journals. If they are smooth, or even reasonably smooth (some visible ridges, but they are smooth and do not "catch" a fingernail) you are probably fine with just new bearings. Will you get 300,000 mi out of such a "freshened" engine? Nope, but you may well get 50-75k miles with no problems.

The 4.0 will go up to 300k if maintained (just change the damned oil), so at your mileage it's very possible your engine is not as bad as you suspect.

Do some reading on in situ ring and bearing jobs, and don't be afraid to tackle it. You will need a torque wrench, but not many other specialized tools.

Your 4.0 is one of the very few OLD technology engines (cast iron head and block w/ pushrod valves) that you can still "rebuild" in this way, which goes a long way toward explaining why everyone advises against it these days.

BTW, I've been wrenching for almost 40 years, and have operated automotive shops as well as done aircraft work (licensed FAA aircraft mech), so I do know something about this.

Bob
 
Ecomike said:
What is your cold and hot oil pressure? Oil pressure at cruising speed?

What kind of noise is it making?

Does the noise increase, decrease, or go away after warm up.

The 4.0's are notorious for being noisy beasts. They are also known for making well over 300,000 miles while complaining all the way with scary sounding noises!

Yours is barely broken in!

I would make sure what the problem is, if it is a problem first!

Low oil pressure limit at hot idle according to Jeep is a dismal 13 psi! Low enough to scare the hell out of most of us, but apparently OK for 4.0's.

Well, it was the guy that I bought it from that told me it was rod bearings, but I thought those got louder as RPM increases and cranks were noisy at idle. This knock is throughout the RPM range. From the maintence that I've done, I've come to the conclusion that this guy sucked at taking care of this XJ. He must have had overheating issues b/c he said he replaced thermostat and flushed the radiator, but I think it's either the e-fan not working or might need a new mech. fan clutch b/c it'll go over 210 at idle. So, not sure how hot it ever got, but that certainly can't help.

As for oil pressure, I think I'm going to pick up a new sending unit tonight. I haven't driven this in 5 months, but I remember it getting low at hot idle - under 20 mark, but when looking under the hood today, I saw that the connector was half hanging off and the pin that it slides onto was bent downwards. I rebent and secured connector, did a fresh oil change and it's now reading 40 on cold start, 40 while cruising, but will dip to 30 at hot (a lil over 210) idle. Just seems too good to be true. There also isn't much if any fluctuation when I rev the motor. Seeing how this is my first Jeep, I just don't know if that is normal? It'd be a first for any of my vehicles (my S-10s didn't even need tachs b/c I could practically watch the oil pressure to know how hard I was revving it!!).

I've already tightened flywheel bolts and the noise is present whether under load or not. Everything has fresh fluid now w/ the exception of power steering which is for tomorrow. I plan on replacing the stock exhaust manifold not b/c I know whether or not there is a leak, but just b/c they're prone to failing. I also added lil over 1/2 bottle Sea Foam to my fresh 10W30 oil change today, so I'll wait and see if that quites down this noise or not.

The only reason I'm worried over this is b/c the only other Jeep I can compare this to is my brother's '00 XJ - he has over 180k and it's quiet as a mouse. Must be the fluke from hell b/c from what I've heard, all 4.0s are noisy and well, I don't want to jinx him on the '00 issue...
 
Based on your update/reply I would try adding a half quart each of Marvel Mystery oil and Lucas oil additive. If the noise goes away after warm up or at cruising speed with these additives it is probably something like sticking lifter noise or loose tapets.

If those two additives have no effect at all after about 30 minutes, then you might have a bearing, valve or other equally unpleasant problem developing. :eek:
 
Ecomike said:
Based on your update/reply I would try adding a half quart each of Marvel Mystery oil and Lucas oil additive. If the noise goes away after warm up or at cruising speed with these additives it is probably something like sticking lifter noise or loose tapets.

If those two additives have no effect at all after about 30 minutes, then you might have a bearing, valve or other equally unpleasant problem developing. :eek:

Well, I did add Sea Foam which should still free a lifter, etc if thats the issue. Do you recommend adding the MM & Lucas combo to my oil with the Sea Foam still in? Im okay with draining a quart, but I dont want to do a full change after a day.

Also, you stated 30 minutes. Is that all it takes? Ive seen people leave SF & MM in for 500 miles and then do full changes. Will 30 minutes of idle do or do I have to roadtrip it?

Appreciate the help. Hopefully something frees up or its an exhaust leak. In the meantime though, I may start looking for a yard engine for a rebuild to have ready in the garage just in case...
 
gone postal said:
Well, I did add Sea Foam which should still free a lifter, etc if thats the issue. Do you recommend adding the MM & Lucas combo to my oil with the Sea Foam still in? Im okay with draining a quart, but I dont want to do a full change after a day.

Also, you stated 30 minutes. Is that all it takes? Ive seen people leave SF & MM in for 500 miles and then do full changes. Will 30 minutes of idle do or do I have to roadtrip it?

Appreciate the help. Hopefully something frees up or its an exhaust leak. In the meantime though, I may start looking for a yard engine for a rebuild to have ready in the garage just in case...

Good point on the possible exhaust leak being the noise source. I had that problem myself recently with my diesel. I thought it was normal, LOL, cause it was diesel!:doh:

I doubt if half a can (6 oz?) of Sea foam is a large enough quantity to do the trick (loosen and clean the lifters) and it is very expensive. I have used MMO ($7-8/quart) for over 30 years and Lucas the last 2 years. I have had great results with either one by itself and even better results with both. The two do different things. The MMO is a thin cleaning lubricant and Lucas is a thick heavy body lubricant. They counteract each other on the oil pressure issue.

The MMO helps free up sticky hydraulic lifters and the Lucas resists heat breakdown and thining and helps keep the lifters pumped up when the oil gets hot. The combo quites the hell out of my noisy lifters. Mine goes from sounding like a jack hammer to sounding like a well lubed sewing machine with these two additives. Mine is still noisy on cold morning start ups but only for a few minutes.

No need to change the oil, just replace the one quart with the two additives (1/2 quart of each minimum) then check periodically and keep the oil filled up till your next normal oil / filter change.

On the 30 minute issue, best to take it out for a good run on the open road, but a 30 minute idle with periodic run ups to 3000 rpm will work too.

I mentioned 30 minutes as the point at which, if the noise is still the same at all speeds, I would give up on the idea of lubricants solving the problem and start planning some engine detective work or a swap/repair/rebuild in the near future.

I actually use one quart of Lucas and one quart of MMO in my 4.0!
 
Alright, I'll give that a shot. SF is actually 10oz, but it says it treats 15qts, so I only used 1/2 can. I actually have some Lucas lying around, so all I need is to pick up the MM. Post my results later...
 
Quick update -

Replaced oil sender today. 60psi cold!! I drove for about 15miles and did some slow cruising on the beach in 4HI. Temps got up to high 220s (have an overheating issue I have to tackle :mad:). Anyway, at that temp, I'm seeing 20 idle and 35-40 at 1500 RPM cruising. When it gets back to 210 on the highway, I'm seeing 30 / 45-50 respectavly.

I'm really hoping that this is an exhaust leak. I know it's hard to explain noises, but when I passed by a construction area that had diesel powered pumps running I thought to myself that is what my engine kinda sounds like. Chattery. I've had it "diesel" before when I sank it in a water/mud hole, so not like that - that was WAY loud, but afterwards my motor seemed quieter than before I entered the hole. I almost wondered if it was a manifold crack that was sealed w/ mud. Is that even possible? It is original, so it has 16yrs and 167k on it. It sounds like it's coming from the lower end though - not top of motor and it's louder on manifold side than passenger. Previous owner said it was rod bearings and that it'd been making that noise for a lil over 2yrs. I just figured it was and after the brakes went, he said screw it and sold it before it just blew up. Guess I need to order an APN header to find out for sure.
 
Back
Top