Rear Main Seal replacement - dig me out of a hole??

[Jim]

Hey Folks,

My rear main has been leaking and I decided to tackle the project. (1990 258 / 4.2). The difficult part of the project - removing the upper seal half - is the difficult part and I just put myself in a hole by breaking off the punch at the block (extends about 1/16" - not enough to grab).

I've tried punching / pushing on the other end of the seal - the broken punch bit is not pushing out of the block. The upper seal is not moving.

Is this transmission removal time or does anyone have a tip to resolve the issue with the motor and trans in the jeep?

Thanks,
Jim

[JandDGreens]

Is it so small that you can't drill into it? Just wondering if the smallest easy out would help turn it free?

[The StRanger]

If ya feel confident you can loosen the main bearing caps, and use a pry bar to lower the crank.
only about 3 or 4 threads.
That should be enough to slip it out. Just DONT turn the engine over.

[Java]

I'd try a dremel tool with a titanium bit to make a small hole in it, screw in a screw and pull it with pliers. Or just destroy it with the dremel and take out the pieces. If you haven't removed the upper half and it's still servicable you can leave it, clean the surfaces all around it and coat them with anerobic sealer before you put them together. I'd actually do that even if you replace the upper.

[Java]

Just saw it and I like Sam's answer better. :thumb:

[FINOCJ]

I've been working the sbc seals over the last week....Getting the top half of of the RMS out is a PITA....as sam said, suggest loosening the main bearing cap bolts a bit....I actually test for what the torque is first, then I know what to tighten them back to....Additionally, I found it helpful to have a helper turn the crank by hand to help move it out, and same when putting the new one in - kinda helps feed it in....not sure what Sam would say with the bearing caps loosened a bit and turning the crank by hand, but that is how I would do it....hopefully not too much damage.
https://beamingpix.com/images/2020/05/10/P_20200510_171345-1.jpg
https://beamingpix.com/images/2020/05/10/P_20200510_155742.jpg

In the one in mine, the split section of the seal was not ideally offset/clocked at bit from the cap/block mating surface - if possible try to offset the the seam between the to halves so they are not perfectly matched up to the mating surface between the bearing caps....in other words, not like this pic....but a smidge of RTV on the bearing cap mating surface is probably helpful....

[Jim]

Thanks folks.

Sam - is your comment of NOT rotating the crank with loosened bearing caps related to a main bearing rotating and not having the bearing split match the mating surface between the block & bearing cap? If that's the concern, I could see, when it's time to tighten the caps, removing one bearing cap at a time to ensure the bearing halves match the seam for the block to cap. Make sense?

I'll spend time with it Sunday... News at 11...

[Jim]

I loosened all main bearing bolts about 1.5 turns. This seemed to give a decent amount of drop. Word in advance - once you loosen those bolts expect more oil to come dripping down from the bolt cavities.

I punched a bit at the other end of the seal and noticed the broken punch bit had slightly protruded. Some side to side pushing on the bit and then needle-nose pliers - pop and out. One item off of the list.

The seal seems to be firmly stuck in its channel. When I'm hitting with the punch I'm debating if the punch diameter is too large and I'm hitting the block or if I'm actually hitting the seal. I've tried smaller punches and am now giving good research to the size of the channel the seal rides in.

Some progress.

Thanks!

[Jim]

IT's OUT!!!!


Pix and details shortly

[Jim]

I went with Sam's advice to lower the crankshaft by loosening all of the main bearing bolts 1.5 to 2 turns (13 turns is full removal). I then, gently, pried the crankshaft "out" of the block at cyls 6 and 5. I also pressed the clutch in as my mind thought it could hinder the crankshaft from easily moving outward from the block (to give some space to allow the upper seal to move / broken punch to be removed). I don't know if the C/S moved much.

From there I worked to clean up the other end of the seal / block area. I wanted a clear view of the U-Channel the seal rides in - where can I place the punch so that I know it's not resting / hitting the block. In the end - I wasn't able to get a clear view of that side. I did have a clear view of the U-channel at the broken-punch side. While I did hit a time or two at the difficult to tell end of the seal I wasn't satisfied hitting at that end - am I hitting the seal or the block.

I felt the broken punch end again and the broken section felt that it had come out a bit. I grabbed a pry bar and gently pried fore and aft on the end - it moved a bit. Needle nose pliers and it popped out. A reassuring step in the project.

Then to resume seal removal. I stayed away from the "unclear" end of the seal and figured I'd try punching the broken-punch-end of the seal again. I grabbed the original larger diameter punch as I could see the U-channel and know I wasn't going to be hitting against the block. It took about three or four solid, heavy hits (more force than I would have anticipated) - but it moved. A couple small hits and I was at the end of pushing it with a punch. Needle nose pliers and it readily slipped out of the channel.

I'll now tighten to spec (80 Ft-Lbs in a 40/70/80 Ft-Lbs step-up - via Jeep service manual) the loosened main bearing bolts. I'll then turn the crank 90deg to inspect the sealing surface from damage I might have inflicted - repairing / smoothing as needed. Then a 180 degree turn for the other area.

A significant step in the project.

Thanks folks for the help!

[Trevor?]

If you had to do it over again, what would you think about using a brass punch? I'm thinking one could swing at that a little harder without worrying about marring up the block or the crank... that and they tend to bend well before they break.

Thanks for posting this. Looking forward to seeing it go back together. I may be needing to do this soon.

[Java]

This is what I meant about the anerobic sealer, but said so poorly. It seals up the area that is prone to leaking between the two halves. You can't use RTV, it won't dry and will not work. I did this to my 258 and my 4.0, neither ever leaked again.

https://www.fourwheeler.com/how-to/engine/1803-how-to-replace-a-jeep-4-0l-rear-main-seal/

https://www.fourwheeler.com/f/163209903.jpg?fit=around%7C875:492

https://www.fourwheeler.com/f/165603412.jpg?fit=around%7C875:492

[Jim]

what would you think about using a brass punch?

Hindsight's 20/20. This project is a first for me and "I'm learning" is certainly on the table.

Having a long punch such that the head of the punch is near the bottom of the bell housing makes hammer swing easier (for me). The shorter punches (that I broke), are usable, but the hammer location for the swing is awkward for how I was working.

My important "learned the hard way" item on the project is to 1) have a clear view of the U-Channel. That way I could clearly see that the punch was over the seal and NOT resting on the block. The hits were so firm that it felt like the punch was resting on the block and not on the seal. Once I _knew_ I was on the seal and not on the block, I was OK giving it a firm / hard hit - where after a small handful of firm hits it moved.

[Jim]

This is what I meant about the anerobic sealer

Thanks. I'm with ya!

I read the steps in the service manual - along with your anerobic comment - and other write-ups. LocTite 518 is one product listed - but it's not generally available in local stores. The Permatex line is available and is what I'll be grabbing while out today.

Here's to hoping I won't see oil drips!

[FINOCJ]

There is nothing fun about replacing a RMS - the old rope style seals are even more fun getting them....really, this should be done once during assembly - I don't know that doing it in vehicle will ever work perfectly, but if your loosing lots of oil then it will certainly help and keep it driveable....If you are trying to stop an annoying but meaningless drip on the floor, I wouldn't bank on much improvement....but you got it done and learned something...hell, I just installed my intake for the 3rd time in 8months and my valve covers for the 3rd time as well, re-inspected my quadrajet again (and made a great improvment), and I am still learning and the jeep is hopefully getting better and yet its nowhere near decent...but then again thats why I buy old POS's...My new philosophy with the willys is it doesn't really matter - just BTFO of it when necessary and don't be afraid to rip it apart and eff it up - its just an old jeep!

There are lot of different types of sealers, gasket tack, RTV etc....I have about 7 tubes/jars of different stuff, and am still learning what applications I like using what types.....Here is one simple summary:
https://www.hemmings.com/stories/2013/09/13/tech-101-how-to-use-the-right-gasket-sealants

[Jim]

My big picture is getting this clutch through the season. I wish to do a reman motor this winter. The large (open palm sized) puke of oil at the gas station near Parachute on the way to Noab last summer was an eye opener (a long freeway day). The RMS started dripping - just a quarter sized dot after being parked for the week - about a year ago. The motor job is on my radar and I "hoped" to make things last. The large puke of oil put some worry on my mind that the clutch might get soaked and cause issues this summer. So long as the drip is much less than what it's capable of, I should reduce some concern for clutch reliabilty this summer.

Years ago, I drove an 80 MG-B from LA to northern IL (helping family). The car had a known oil issue when I left the west coast. I quickly realized it was the RMS. After quickly pumping through two or three "quart singles" I quickly realized I would need to buy oil by the case. The trip ODO was used for oil checks as it would process oil faster than a tank of gas. The clutch worked valiantly until about 250 miles from home in Illinois (rolling farm fields - no mountain grades). At highway speeds the "Illinois hills" would see the speedometer dropping with the tach climbing - the clutch was soaked and slippery. I don't want to experience this with the jeep and was happy to try to resolve or reduce the issue with this seal replacement.

I believe I have worn rings which is causing more crankcase pressure. I'm considering removing the PCV valve and going full open tube from valve cover to intake - to help reduce crankcase pressure. The jeep, at this point, is decently happy with two lane speeds / throttle settings - but freeway & heavy throttle - not so much. One problem free summer is my goal before a large replacement to happen.

[FINOCJ]

I'm considering removing the PCV valve and going full open tube from valve cover gasket to intake
Assuming the pcv valve is functional, open tube vs open valve shouldn't really matter....There is no good way to reduce crankcase pressure from blowby (I just spent the last month working on it in the willys....it has a road draft tube instead of a pcv system, but similar idea to your open tube, except it vents the excess pressure and dumps the oil on the road below as you drive instead of feeding it back into the intake for combustion (was a different time with different concern over emissions etc). There are oil traps/catch cans that can be installed in the pcv hose to reduce the amount of oil going into the intake if its becoming a problem and affecting engine performance or fouling plugs etc....also give an idea of how bad the blow by is by how much oil collects.....I had issues with blowby in my 4.2 cj7 - except the pcv feed into the oil filter housing and not into the intake or below the throttle body at the base of carb - so it would ruin paper element air filters rather quickly and then get sucked into the carb clogging the carb....Much as you say, its worst when you are at highway speeds (high rpm with no OD or large tire/gearing issues) or in the mts pulling hard. The wagon is doing the same thing right now, and the crank case pressure is pushing oil out of every seal and gasket there is.

Oh - and just my suggestion - a new/rebuilt/reman engine is awesome (its made my cj5 a different, totally reliable vehicle), but one day I'd suggest considering doing some gearing to help move those 35s along and allow for full use of your 5 speed :D

[Trevor?]

How many miles are on your 4.2, Jim?

[Jim]

187K on the clock. "I believe" the motor has not been opened but I am not certain.

I purchased it in 06/2011 with 153K on it. The guy I purchased it from filled oil and gas and turned the key - little to no mechanical involvement with it. Somewhere before him the jeep had been modified - drivetrain, lift, and perhaps specific to your question (motor work) is that it had been converted from original carb to Mopar MPFI. The head might have been swapped (one person I spoke with who looked at the motor said it has a newer head - I don't know casting ident). I don't think the bottom end had been changed / worked on but I don't know. I'd like to chat with the person who mod'd the jeep (though by now I have most questions answered - figured out what I bought).

08/2011 compression test (I think I read that the 4.2's compression numbers are in the 120 to 150PSI range. 4.0's are 170 or 190PSI IIRC). Hmm - at that time, compression was decent. I should re-check.

Grey hand push to block compression tester used. Only one hand used to hold it to the block (some seepage possible). Air filter removed. Throttle plate opened. 4-5 compression strokes. Partially warm motor. Front to Back: ~145, ~145, ~150, ~145, ~140, ~145

[The StRanger]

I love it when a plan comes together.

[FINOCJ]

What do the plugs look like today...the ones in the pic from 9/11 look okay....

[Jim]

05-2017 is the current plug pic set (20K miles on'm). I think (famous last words) I changed them last year - but no pix. 1 and 2 look normal. 4 mostly good. 3, 5, 6 - abnormal.

I was told by a mechanic, on that first set of plugs, what they looked like to him and the reply was "oil fouled". That's my source for my oil fouled statement. Looking at plug condition pictures on the internet they're not dark, wet and oily - but I certainly am burning oil (always carry it and check it / fill it every trip (often it's near the bottom mark of the dipstick and I fill to the top mark). That's in 150 to 200 miles.

[FINOCJ]

Looking at plug condition pictures on the internet they're not dark, wet and oily

agreed...you've got some heavy ashy deposits on there, so its definitely not clean full combustion, and a bit of carbon build-up, but not the typical dry black sooty fouling of overly rich and oily, and certainly not the extreme wet oily fouling.....a slightly hotter plug rating might help keep them cleaner and be a good solution to keep it running over the summer. Those old I6 just keep running - rebuilding or replacing is usually based on when you are tired of dealing with a tired engine and not because it blows up....they tend to dye slowly, very slowly.

May or may not be worth your time and effort - but a combination of a wet vs dry compression test, or a leak down test might confirm how bad the rings are and if the valves are sealing properly. Could also a some issue with valve train wearing and not getting enough lift of the valves (kind of guessing there - but the ashy deposits are interesting). You are right at my limit of knowledge or confidence - but as the plug fouling is not super oily, but combustion is not completely right, I am suggesting something going on with the valves. In reality, its probably a combination of oil consumption from ring blow by and valve issues, and the resulting increased crankcase pressure just compounding matters.

[Jim]

And a reman long block will tick all of the boxes...

When doing a swap I'm looking to keep existing setup for replacement (4.2 vs 4.0 and v-belt vs serp) as the york comp setup "fits" this setup. I'd really have to be convinced 4.0 with serp was better before making the change.

It's unlikely I'll pull plugs this season for any inspection or comp testing. Cyl #1 is difficult to access with the york mounted (something one would think would happen only on a modern, tightly packed engine bay).

[FINOCJ]

I love the 4.2, but I'd consider a HO 4.0 with the MPI fuel injection vs the early Renix fuel injection (which is what I think is retrofitted on your existing set-up?)...Are planning on keeping you existing FI set-up or going all new? I am pretty sure you can run later 4.0 heads on a 4.2 (and its a nice improvement), but not sure if that also allows for the MPI set-up - I would guess yes.....but yup, one change leads to another and another like dealing with the compressor etc....For me, in addition to cost, having to deal with different fuel tanks and delivery system is the main block to getting some sort of TBI on the cj5.

[FINOCJ]

It's unlikely I'll pull plugs this season for any inspection or comp testing. Cyl #1 is difficult to access with the york mounted (something one would think would happen only on a modern, tightly packed engine bay).

I have to disconnect the v-belt, and disconnect the generator from the bracket, and the remove the PS pump and bracket as a unit to access the driver side valve cover and #1....1957 sbc - but the PS pump and bracket is all custom bubba fabbed (albeit it works and probably better than I can fab), things get odd.....

[Jim]

I appreciate the low end torque this motor offers though I wish it didn't run out of breath at the high end (a fresh motor would likely help this condition).


I'd consider a HO 4.0 with the MPI fuel injection vs the early Renix fuel injection (which is what I think is retrofitted on your existing set-up?)

I'm told this is equivalent to the Mopar 1995 4.0 setup (I don't know if this is what you'd call early renix FI). I _might_ have the 4.0 head (which I hear flows better than earlier 4.2 heads). Emissions classifies this as 1994 model year. I need to document these major motor parts - what's stock / what do I have (leading back to the question of finding the person that modd'd the jeep - they might be FoCo local).

I plan to keep the existing FI setup. Intake & exhaust mans stay. Intake is new for injection though I think exhaust is the same - uncertain - it has an exhaust manifold O2 sensor - uncertain if that existed on the carb setup.

[FINOCJ]

I plan to keep the existing FI setup. Intake & exhaust mans stay. Intake is new for injection though I think exhaust is the same - uncertain - it has an exhaust manifold O2 sensor - uncertain if that existed on the carb setup.

IIRC, the last version of the 4.2, carb and all, and which went into the last CJs and YJ wranglers through 89 (I think?) had auto-metering carbs for altitude fuel mixture adjustment - so I am pretty sure there would have been some sort of O2 sensor. Based on todays EFI, it was pretty crude, but it worked - I drove my cj7 from the top of Mt Antero (14,000ft) and home to FL and back a number of times and I don't ever remember adjusting the carb - compared to either the Qjet or R2g I have now, it was a complex carb - albeit behind the times as most GMs had gone to TBI in the 80s. Jeep sorta skipped the TBI revolution and hung on to carbs for longer than most, then made the jump straight to EFI (possibly due to AMCs demise in the mid-80s and the Chrysler take-over in the late 80s).

I haven't messed with a jeep 4.2/4.0 straight six in quite some time...but 1995 would have been the MPI 4.0 HO (high output)....It was like 190 hp when it came out which really does put the early Renix 4.0 and carb 4.2 to shame...A lot of it was head design and multi port fuel injection - and as you want, that kept most of the classic low end torque of the I6, but gave some pep to to the higher end (albeit - its still not a 3000 rpm type motor for extended periods). Guessing some changes were made to the cam as well at the time to take advantage of better flow....
The old 4.2 was sorta diesel like...relatively low hp, small power band for gas engine, but lots of torque and it just runs even when mis-treated....
There was a willys wagon for sale around here 3 or so years ago that had a HO 4.0 swapped in - I wish i would have bought that one - it was out of my price range and I wasn't serious about buying yet...The ol wagons came with a flat head straight six (and I kind of wish I had bought one with an original style engine)...but those old L226 just don't have much function in todays driving. Anyway, for whatever reason, while those early L6s were oem, but the later AMC/Jeep straight sixes apparently are a PITA to fit in the engine bay and swap in.

It'll be fun to see your engine swap take place....There is part of me that debates just dropping the coin for a new sbc 350 crate engine for the wagon....old cars are fun, but more fun when they run like new.

[Jim]

old cars are fun, but more fun when they run like new

`was out this morning and a "nice" (worked on) 40's / 50's era "truck" drove by to the stop sign. Stake side flatbed. No paint - all rusted patina look. The sound when it pulled away - modern motor and drivetrain under that old body.

[FINOCJ]

The sound when it pulled away - modern motor and drivetrain under that old body.

I just want my old junk to run like it would have when it was 'new' back in the day....While I wouldn't turn one down if it was done right, I am less interested in an old body on modern frame/drivetrain.