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Pulling Engine

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OK Y'all - It has been a while since I posted on here and I apologize for that but I have been extremely busy with work lately.


I am finally getting around to pulling the engine on my 87 MJ (4.0 - 5spd). I am tired of getting better gas mileage than oil mileage. My plans right now (engine wise) are to replace the rear main seal, hone the cylinders, install new piston rings and new bearings.


While I am at it, I will also be replacing the motor mounts, as mine are gone, install a new clutch, install a new throw out bearing and pilot bearing. I also need to replace the transfer case because 4 wheel drive has stopped working.


I have a couple of questions before I go any further with what I have been working on. I have the engine ready to come out - except for the fact that I still need to disconnect the fuel lines from the fuel rail. I have a disconnect tool for a newer style Dodge but this one will not work for disconnecting the fuel line on the MJ. What type of tool do I need for this or is there just a special trick to doing it without a tool?

Secondly, I have fairly easy access to the local Pull-A-Part salvage yard. This is where I plan on getting a replacement transfer case for the MJ. I have already looked through their inventory and they only have one MJ and it is an 86 model. They do, however, have several Cherokees on site. I really don't know a whole lot about transfer cases and was just wondering is there was a particular one I should be looking for. Can some one suggest a good year model to pull one from? Are there distinct marking to tell them apart?


Any information will be greatly appreciated. I will post new pictures as soon as I get to a good point in the process so that I can start updating the build up of my MJ.


Thanks - KMAPRO

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As for transfer case, there are differences in the spline count. 21 and 23, I think. I think yours is 21. I remeber that 87-88 used the 21 count. I think some of the later 4 cyl. used a 21 count spline.


I can't remeber how the fuel line came off. Sorry.


Now as for oil going into the filter. Search for the topic 'Blow-By'. Its not really blow-by but its what Jeep 4.0Lers refer to this condition by. I have gone through this myself. I was useing about 1-1.5 qt per week. It was probably 250 miles per week.

I did the usual of new CCV lines etc. It helped for a while. My solution was to up grade to a 'nwer' valve cover. I used a 91-95 valve cover. The 90 degree elbows are suppose to handle the oil better. The later pressed steel ones are suppose to be better than that. I have recently bought a late '95 valve cover. It has the 'grommet' style CCV fitting like the latter pressed steel ones.

I also did a big hose late style CCV hose mode like seen on MADXJ site. I had to cut and splice the hose to fit the Renix intake. Its a bit longer.

I think most of the problem is caused by the valve cover gasket not sealing well. I tried a few cork gaskets. The worked for a while then lost their compression. I would probably try a FelPro rubber/cork gasket. I would put some gasket seal on the gasket to valve cover surfaces, to bond it to the valve cover.

I also was on a thread on Jeep.com board. One poster said there was an 'unofficial' factory mod. You cut the oil towers inside the valve cover 2 inches shorter. Then drill a 1/2 hole on each of the two towers, another 2 inches up and on the rear side (or rear side of engine).

I think Pete posted a link to a CC post on the same subject in the Jeep.com post.


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Hold up a little bit on replacing that 231.


How do you know your 4wd stopped working? How are you 100% that it's the T-case? Sure it's not the CAD?


To clarify, in case you do need a new T-case, you have a short shaft 21 spline input. All Pukey BA 10/5s used the 21 spline, AX-15s used 23. AW-4 used both, I believe the changeover year was mid 90 or 91 from 21 to 23. 4 cylinder cases will be useless to you, as they have a longer input shaft and probably won't bolt up. You'd need to be aiming for an 87-90 4.0 case.


Also, your throwout bearing/slave cylinder are going to be one piece.

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I'd like to know your reasoning behind honing the cylinders and installing new piston rings. Are you having compression problems? What is your compression on each cylinder? Do you attribute your increased oil usage to it being burned in the engine because of out of spec. ring gaps?


You might be doing too much work by honing out the cylinders and installing new rings. I wouldn't do that unless I was absolutely convinced they were a problem. If your engine is burning a lot of oil, I'd look at the cylinder head - specifically the valve stem seals and valve guide clearances. You'll probably benefit a lot more by getting the head reworked (multi-angle valve job, repair and loose valve guides, new valve stem seals) than you would by replacing the piston rings.

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OK here is more info...


Truck info:

1987 model

4.0L I6

5 spd manual transmission - I believe it to be the crappy Puegot BA10/5 (I think that is the right info)

Transfer Case - I believe it to be the NP-207 because the information I have read says that the 207 was used until 87 and then the 231 replaced it. I don't know if "until" included 87 or not. I don't know how to tell.

Front Axle - Dana 30

Rear Axle - Dana 44

I believe this to be a "Metric Ton" package due to the fact that it has the D44 rear end and it is a long bed.


What I have already done:

I was experiencing oil blow-by as someone mentioned. I have already upgraded to a newer valve cover. I am running a valve cover from a 96 model and the felpro gasket. Other than patching some holes in the floorboard, that is all I have done.


Why I am doing this:

The valve cover swap helped with the blow-by, but did not eliminate it. I also keep fouling spark plugs at the #2 cylinder (like every other day before I installed a no-foul adapter). For these two reasons, I believe the rings to be bad on the #2 piston.


I also have a very bad oil leak coming from the rear of the engine - rear main seal. I am literally going through 5 quarts a week. I am not burning it - I am leaking it..or it is marking it's territory.


The engine has a little over 150k miles on it. I figure the cylinder needs a good honing while I have the piston out for ring replacement. If I am doing one of them, I might as well do them all. Since I will also have the oil pan off to replace the rear main seal and the pistons out, I might as well go ahead and replace the bearings while I am at it.


When I am at a red light - truck out of gear and foot off the clutch - I hear a slight knock or bump coming from the transmission. If I push in the clutch, the sound goes away. I can only assume this to be the throw out bearing/slave cylinder. Any body got any other ideas as to what this could be?


I know 4 wheel drive is not working because I was recently doing some yard work and had to hook to a small stump to pull it up. I shifted into 4 wheel drive, tightened the chain and all I did was spin - rear tires only. The truck is running street tires (hand me down from my father who used the truck as a company truck until he sold his business), so it doesn't take much for it to spin on wet grass under load.


Now it does shift down in to the lower gear range, but I get no pull from the front end at all. I do not get any pull from 4 wheel Hi either.


I know that the 4 wheel drive system worked when I got the truck, because I used it for similar projects around the yard and never had a problem. I have always had 4 wheel drive trucks, but have never had to work on them because I never had a problem with them. So, I can only assume it is the transfer case. Sorry, but I have no idea what the CAD is...


If someone could tell me how to check the transfer case out, I would appreciate it.


Now that you know the full story, does it sound justifiable to be doing what I plan on doing? I am open to other suggestions. My goal is to have the truck back on the road within 2 weeks. I am only working on it at nights and on the weekends - and when funds allow. My 01 Ram 1500 uses too much gas to be driving every day - which is why I have the MJ any how.

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NP 207 was 86 only in the MJ. You have a 231.


I bet you anything your T-case is fine, if you're not getting any noises from it. Best way to check, is with the truck off, shift into 4wd, crawl under, and see if you can turn the front driveshaft. If you can, T-case is toast. I'm betting you won't be able to.


The CAD is your Central Axle Disconnect. It separates the two pieces of the passenger side axle shaft. It's controlled by a vacuum motor, run off a switch on the T-case. Many, many things can, and will, go wrong with this system. Your best bet is to lock it over and not have to worry about it anymore. Easy enough to do : viewtopic.php?f=9&t=18415

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Thanks Geneovast for the info.


If this turns out to be the problem - will it hurt if I make the truck full time 4wd? I am assuming that this is what it would do. Remember, I am using this truck as an EVERY DAY driver. Will I experience excessive wear and tear?

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quick vocab lesson... your truck is incapable of "full-time 4wd". that particular phrase is associated with systems that allow 4wd use on dry pavement. Yours is a "part-time 4wd" where you should not use 4wd on anything but slippery surfaces (gravel, dirt, snow, etc).


that all being said, the t-case lever controls 2wd-4wd. :thumbsup: as long as it is in 2wd, your truck is in 2wd. The CAD controls whether or not the front wheels get anything from the t-case after you've shifted the t-case into 4wd. Jeep eventually did away with the CAD system completely in the early 90s. It didn't give any measurable improvements in anything and was a pain in the butt to keep working properly.



One thing that may pop up after locking the CAD is vibrations from your front driveshaft if the U-joints are bad. But if they are bad, you should be replacing them anyways. :D

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Hopefully these will help explain... The second picture is what you were experiencing, except in your case, the front wheels would be stationary, one or both rears would be spinning, and only the middle shaft in your front axle would be powered.



Basically, the old CAD systems had two points for engaging 4wd. Both have to be engaged for 4wd to work. Locking over the CAD will not cause you to be in 4wd all the time, as illustrated in the last picture. Everything's rotating, but the front and rear axles are not locked together, front isn't powered, so you're good to go. As stated before, Jeep eventually did away with the troublesome CAD anyway, and the passenger side axleshaft in the front went to one piece. Also, all Select-trac Jeeps(aka AWD and Full Time 4wd) did not have a CAD.


edited/updated for clarity.

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Don't disagree with anything you plan to do on the engine, except the ring job and honing the cylinders. Still more likely to be valve seals fouling #2 plug. At least a compression check first and compare all the cylinders. If #2 is low, then squirt some oil in the cylinder and recheck. If that brings the compression up, only then would I consider spending time and money on rings.

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Thanks Harper - I will do that first then.


As a side note, I did talk with my father concerning the problem over the weekend. He said that some of his workers drove the truck and ran it hot. It could very well be something in the head or the valve seals.


I will check the seals first and then decide which course to take.

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OK - I am glad I listened to y'all.


Did a compression check this weekend and compression was good across the board. Looks like I will be replacing the seals.....


I will still need to pull the engine because I have to replace the motor mounts and do the rear main seal. I know I could do the seal with the engine in the truck, but the oil pan is stuck and I have not been able to get it off. I have tried everything that has been suggested in other postings I have made on the subject - still no luck.


While it is out, I plan on painting the engine bay and the engine as well.


I will start posting pis of the build as I go along in the proper forum.

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be very, very careful when moving parts around in the engine bay. well meaning owners have caused themselves all sorts of headaches from flexing 20 year old wires and other plastic parts that have become brittle over the decades.


make extra sure you got all of the pan bolts. :thumbsup:

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Everything still seems good and flexible on my end. The only exception is the wire loom surrounding the wires in places. It just crumbles in my hands when I pull it out.


Thanks for the advice and I will make double sure I get all the pan bolts!!!

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