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Rear Main seal issues...to say the least

O

Ol' Smokey

NAXJA Forum User
Location
Hillsboro, OR
Ok so I'm new to this forum and looking for a little help/advice.

6 months ago I picked up a 91 comanche for $700. Wanted a pickup to caddy my bikes around. 4.0L, 5 speed, 2wd, 120,000miles. Nicknamed "Ol' Smokey" cause the rear main seal is leaking oil all over my exhaust giving me a great high everytime I drive it over 5 miles... Great huh?

I've put it up on the lift, unbolted some suspension members, took out the oil pan, unbolted the lower main seal housing and after a long time trying to get the old seal out, finally got it out. Replaced the seals (greased them liberally) and now is leaking way more than it did before. Obviously the seal didn't seat correctly or was put in wrong or something... My question is this: Would it be easier if I just pull the tranny to replace the seal since the truck setup should give me little resistance or should I go about it the same way as before, through the oil pan...? From what I read, this is a common problem and it may take a few times to get the seal to seal correctly.

My buddy who has experience pulling jeep trannies says the only way to replace the seal right is by pulling the tranny. Everything I read, even the Chilton's manual says to go through the oil pan, huh?
 
Although it's entirely possible that you shaved off some of the seal, a leaking Oil Filter Adapter O-ring can look an awful lot like a RMS leak as can a leak in the rear of your valve cover.

Eliminate these possibilities first. Pulling the tranny won't make it any easier.
 
You know I think you may be right, the seal may have shaved off a bit. At least now the seals will be easier to get out since removing the old seals took more than half the overall job time. This time I'll buy a few RMSs. Should I coat the thing in soap or astroglide/vasoline or something? Vasoline is a petrolium product- that may work...
 
get a torque wrench, loosen all the main caps enough to let the entire crank drop a fraction or two, swap the rms (should be alot easier with the crank loose). retorque all the main bolts to spec. reinstall the oil pan.

Because the rms is a two peice deal dropping the trans would be a waste of time cause you'll still need to drop the pan to get the main seal out.
hope this helps.

P.S. vasoline is a really good idea....lube the seal with something petroleum based....I usually use axle grease. put them in dry and they'll fail somewhere between the garage door and the parking space.
 
Ol' Smokey said:
...Should I coat the thing in soap or astroglide/vasoline or something?
Click to expand...

Hell no! You have work to do. Get back to the Jeep!!:D JK

The Hayne's or Chilton's manual says to put undiluted dish soap on one edge and engine oil on the other.
 
Ol' Smokey said:
Ok so I'm new to this forum and looking for a little help/advice.

6 months ago I picked up a 91 comanche for $700. Wanted a pickup to caddy my bikes around. 4.0L, 5 speed, 2wd, 120,000miles. Nicknamed "Ol' Smokey" cause the rear main seal is leaking oil all over my exhaust giving me a great high everytime I drive it over 5 miles... Great huh?

I've put it up on the lift, unbolted some suspension members, took out the oil pan, unbolted the lower main seal housing and after a long time trying to get the old seal out, finally got it out. Replaced the seals (greased them liberally) and now is leaking way more than it did before. Obviously the seal didn't seat correctly or was put in wrong or something... My question is this: Would it be easier if I just pull the tranny to replace the seal since the truck setup should give me little resistance or should I go about it the same way as before, through the oil pan...? From what I read, this is a common problem and it may take a few times to get the seal to seal correctly.

My buddy who has experience pulling jeep trannies says the only way to replace the seal right is by pulling the tranny. Everything I read, even the Chilton's manual says to go through the oil pan, huh?
Click to expand...

When you figure this out please let me know. I have replaced that seal now 3 times along with oil filter adapter seals oil pan valve cover. there is nothing else that can be replaced that could leak oil but yet some how I still leak oil Im down to about a quart ever two weeks which is musch less then before. The leak gets worst has there is any flex between the tranny and motor. I found this out due to bad motor mounts and tranny mount.

Now becuase of this I know its gotta be that rear main and Im sure its got a scratch or nic on the crank or bearing cap. But who knows.

So yah make sure you post when you get your leak fixed please.

Adam
 
Make sure you get a double lipped RMS because the crank may be worn by the old RMS.

Just my .02
 
X2 on the crankshaft causing the leak. It might be turned undersize from wear.
=========================================================

You may have nicked the crank when removing old seal. Look for a nick, dent or anything on the crank that may eat up seals when spinning. It doesn't take much. If you find one you have a problem.
But a brave man and some WET, VERY fine emery cloth can sometimes bring her back. Wrap a strip around crank and buff like an old Army boot.
Clean WELL after sanding. I have fix more then one crank this way.
 
Ol' Smokey said:
You know I think you may be right, the seal may have shaved off a bit. At least now the seals will be easier to get out since removing the old seals took more than half the overall job time. This time I'll buy a few RMSs. Should I coat the thing in soap or astroglide/vasoline or something? Vasoline is a petrolium product- that may work...
Click to expand...

Pour out a cupful or a small bowl of clean oil before you start, and throw the new seal in that. Let it soak while you get the old one out. Then, take the new seal out of the oil and install it - button it all back up.

Hasn't failed me yet...
 
5-90 said:
Pour out a cupful or a small bowl of clean oil before you start, and throw the new seal in that. Let it soak while you get the old one out. Then, take the new seal out of the oil and install it - button it all back up.

Hasn't failed me yet...
Click to expand...

I'll be trying this....

I was always curious about the "soap" thing - any info on that 5-90?
 
I'll write something up as soon as I get the seal in on Saturday (hopefully) and drive it around for a while. I'll try soaking the seal in oil, sounds like a damn good idea. My buddy lives and dies by this "Slick Honey" stuff and says that if that doesn't do it the he doesn't know what can.

If the first seal doesn't do it then I'll try loosening up the main caps. That's gotsta do the trick. Thanks guys...
 
92DripCherokee said:
X2 on the crankshaft causing the leak. It might be turned undersize from wear.
Click to expand...
IM in that F^&*ing boat right now. Always replace he RMS asap, I learned the hardway. :bawl:
 
ParadiseXJ said:
Hell no! You have work to do. Get back to the Jeep!!:D JK

The Hayne's or Chilton's manual says to put undiluted dish soap on one edge and engine oil on the other.
Click to expand...


Just did the RMS last weekend (SUCKED).

But, I followed the Hayne's manual. Dishsoap on the outside of the seal. Engine oil on the lip. Then, I used the end of a zip tie as sort of a shoe-horn to get the top part it. (Also to protect the seal from the sharp edge). Slid right in.

So far no issues (knock on wood).



Oh. Did you put the lipside toward the engine? If the seal is backward... it will leak a lot.
 
JNickel101 said:
I'll be trying this....

I was always curious about the "soap" thing - any info on that 5-90?
Click to expand...

I don't see any real reason for it to not work, but I've never tried it. My granddad showed me about dunking the seal entirely in oil about twenty years ago, and I've sworn by it since.

Maybe a little touch of grease to help it slide through the groove (like that doesn't sound sexual?!?) but I haven't needed even that. And, it makes sense for a petroleum-based something to be used for a seal that lives in an oil bath, so I've just not seen a need to try anything else.

What to do with the oil after you pull the seal out? Dump it in the engine - it's still clean.
 
Ol' Smokey said:
My buddy who has experience pulling jeep trannies says the only way to replace the seal right is by pulling the tranny. Everything I read, even the Chilton's manual says to go through the oil pan, huh?
Click to expand...

So you've probably noticed by now that the friend was wrong. Did you do the step of putting a dab of rtv on the ears? Also check that the rear breather line on the valve cover is clear as that might cause a little pressure buildup in the crank and it'll exacerbate any leaks. Oil pan gasket go on okay? As others mentioned, check the oil filter adapter and the valve cover (back of block wet?)
 
lawsoncl said:
So you've probably noticed by now that the friend was wrong. Did you do the step of putting a dab of rtv on the ears? Also check that the rear breather line on the valve cover is clear as that might cause a little pressure buildup in the crank and it'll exacerbate any leaks. Oil pan gasket go on okay? As others mentioned, check the oil filter adapter and the valve cover (back of block wet?)
Click to expand...

You know what's funny - I never did the RTV on the ears thing, either. After putting in the main halves, there was just enough 'stick-out' that I didn't think it would be a problem.

It wasn't.

Maybe it was just in the cases I've had (they were three,) but bearing cap tolerances I don't like to play dice with. It's entirely too easy to put too much RTV there and screw up your bearing crush and oil clearances, so I've always checked - if I could feel the seal halves sticking out, I just figured that "crush" would handle the rest, and it usually has.
 
Update-

Ok, so got the damned thing changed on Saturday and here's how it went...

Friday evening- drove ol' smokey down to the shop the evening before to make sure the oil has plenty of time to all (most) settle in the pan. I've done this job before with the engine warm and it's like 1000x messier, oil drippin all over the place (your face).

Saturday morning- Jacked it up, drained oil, loosened all oil pan bolts (all 100 of them), pulled starter, unbolted the lower shock mounts and some sort of stabilizer bar that connected the front axle (passenger side) to the frame (drivers side). Axle drooped on the passenger side about an inch or two, just enough to get the pan out. Had to kinda twist it and tilt it to finally get it out. Pulled the lower rear main bearing cap.

Cleaned gasket surfaces on both the pan and the block. Tip- GET THE ONE PIECE OIL PAN GASKET. Spend the extra 15 bucks and get the rubber gasket. DO NOT BUY THE 4 PIECE CORK/RUBBER. Pushed up on one side of the Rear main seal with a screwdriver and it came right out. Replaced the lower rear main seal in the bearing cap with some "Slick honey" (a grease/lube used for cycle suspension). This half of the seal can only go one way. Pay attention to this part of the seal and make sure the upper seal is aligned the same direction as the lower (doing this will make it really hard to screw up) and makes me wonder what I was smoking when I tried to replace the seal the first time. The V-groove facing the front of the engine... I coated the upper seal in the same grease as well as both openings into the seal housing on the block. Use your hands to install this seal as it should slide right in and if you use pliers or something you are more apt to damage the seal or put it in wrong. Replaced the bearing cap (with very little RTV on the "ears" and torqued to 80ft/lb. Replaced (cleaned) oil pan with gasket (takes some trial & error to align all surfaces correctly. Clean your oil pickup as this gets clogged and may affect oil pressure. I retorqued oil pan studs and bolts to specs but forgot to tighten one of the front corners. Added oil, Started up the engine to notice the leak. Since oil got through the seal, it is now seeping a little bit of oil no matter what. Great. oh well. I will retorque in a few days, hopefully that will help.

Replaced suspension bolts and ripped a few doughnuts in the parking lot (great stress relief).

Good news is- Ol' Smokey is no longer smokey and the buildup of oil on the exhaust can now start to burn off. Time to go hope it passes DEQ...

Hope this helps somebody out there.

Ryan
 
Ol' Smokey said:
Update-

Ok, so got the damned thing changed on Saturday and here's how it went...

Friday evening- drove ol' smokey down to the shop the evening before to make sure the oil has plenty of time to all (most) settle in the pan. I've done this job before with the engine warm and it's like 1000x messier, oil drippin all over the place (your face).

Saturday morning- Jacked it up, drained oil, loosened all oil pan bolts (all 100 of them), pulled starter, unbolted the lower shock mounts and some sort of stabilizer bar that connected the front axle (passenger side) to the frame (drivers side). Axle drooped on the passenger side about an inch or two, just enough to get the pan out. Had to kinda twist it and tilt it to finally get it out. Pulled the lower rear main bearing cap.

Cleaned gasket surfaces on both the pan and the block. Tip- GET THE ONE PIECE OIL PAN GASKET. Spend the extra 15 bucks and get the rubber gasket. DO NOT BUY THE 4 PIECE CORK/RUBBER. Pushed up on one side of the Rear main seal with a screwdriver and it came right out. Replaced the lower rear main seal in the bearing cap with some "Slick honey" (a grease/lube used for cycle suspension). This half of the seal can only go one way. Pay attention to this part of the seal and make sure the upper seal is aligned the same direction as the lower (doing this will make it really hard to screw up) and makes me wonder what I was smoking when I tried to replace the seal the first time. The V-groove facing the front of the engine... I coated the upper seal in the same grease as well as both openings into the seal housing on the block. Use your hands to install this seal as it should slide right in and if you use pliers or something you are more apt to damage the seal or put it in wrong. Replaced the bearing cap (with very little RTV on the "ears" and torqued to 80ft/lb. Replaced (cleaned) oil pan with gasket (takes some trial & error to align all surfaces correctly. Clean your oil pickup as this gets clogged and may affect oil pressure. I retorqued oil pan studs and bolts to specs but forgot to tighten one of the front corners. Added oil, Started up the engine to notice the leak. Since oil got through the seal, it is now seeping a little bit of oil no matter what. Great. oh well. I will retorque in a few days, hopefully that will help.

Replaced suspension bolts and ripped a few doughnuts in the parking lot (great stress relief).

Good news is- Ol' Smokey is no longer smokey and the buildup of oil on the exhaust can now start to burn off. Time to go hope it passes DEQ...

Hope this helps somebody out there.

Ryan
Click to expand...

You have probably now discovered why I say to put about four small studs (1/4"-20 - SBChevvy valve cover studs work well here) in near the ends of the long rails on the oil sump. Set the gasket in place, set the sump in place, start the nuts by hand. Go around and start the screws - much easier, with four nuts holding the thing up.

Torque the studs to the same level as the rest of the screws - 7 pound-feet/84 pound-inches. 5/16" screws to 11 pound-feet/132 pound-inches (I'm fairly sure about those, but verify on my site. Figures there are all taken from various FSMs.)

Use studs on the oil sump (four, stamped SBChevvy valve covers,) use studs on the valve cover (two-four, cast SBChevvy valve cover) and it makes things loads easier. They tend to keep everything aligned while you're working, and let you concentrate far less on holding things in place (especially on the oil sump - or the AW4 oil sump. Use M6-1.0x20m/m for those.)
 
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