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  #1  
Old March 9th, 2018, 02:37
4x4JeePmaNthINg's Avatar
4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Rear main seal + oil pan gasket.

Hey all,


As weather is warming up I have this job on the radar.
I know there are many threads showing the process, but what I would like help and advice on are:
. proper tooling
. things to consider and look out for
. I've never done any work like this on the jeep and I want it done right. Are there any parts I should prefer over others?

. I'm generally fine wrenching on anything thus far, that said should this be easy enough for me to accomplish?

I'm really ready to have the jeep not leak anymore.

99 auto
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  #2  
Old March 9th, 2018, 04:46
Dragonlich1961 Dragonlich1961 is offline
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Re: Rear main seal + oil pan gasket.

Be careful and don't hit the crank when you drive the old seal out. Use lots of oil when.installing the new.one.
Make sure the rear portion of the oil pan gasket is seated properly when you torque down the pan. It has a habit of trying to fall into the pan. This causes a big oil leak....
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  #3  
Old March 9th, 2018, 06:29
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Re: Rear main seal + oil pan gasket.

First thing to do is verify.....

I’d be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF.

Everybody, who doesn’t own or have to pay for or perform your vehicle repairs, loves to poke their noggin UNDER the Jeep and come out bearing the false bad news that your RMS is leaking. Many mechanics, friends, and good old Uncle Bob seem to enjoy telling you it’s the rear main seal. Has a catastrophic ring to it, doesn’t it?

A simple leak at the back of the valve cover or other source could produce the same symptoms. You don’t need to be a mechanic to figure this out. If you have good eyesight and a dim flashlight, you’re good to go on your own. Don’t jump on the RMS/oil pan gasket bandwagon right off the bat.

Almost any oil leak on your 4.0 is gonna drip from the RMS area for two simple reasons:

First off, the engine sits nose-up and any oil will run back to the RMS area.

Secondly, the RMS area is also the lowest point on the engine. Simple physics and the old plumber’s adage apply here: “Crap flows downhill”.

Valve cover gasket, oil pressure sending unit, oil filter adapter seals and distributor gasket, in that order, have to be eliminated as possibilities first.
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Old March 9th, 2018, 08:37
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Re: Rear main seal + oil pan gasket.

Get a brass punch for the RMS. It is probably something like 3/16". You will have lousy access on account of the flexplate needing to be back there. It is hard to control the punch, and you really don't want to damage the surface of the crankshaft.

There is an anaerobic sealant needed for between the two halves of the seal. That might not be something you keep on hand.

Bread ties are very convenient for keeping the pan gasket in place on the oil pan while you angle it this way and that in an effort to get it back into place.

If it looks like you might end up getting into the timing cover too then you should probably get a new timing chain and a new chain guide/dampener (black block of what used to be rubber but is now hard as a rock and brittle). Proper replacement of the timing cover involves a special centering tool that is probably only available for a Benjamin, but the harmonic balancer can serve as a centering tool. You will want a good puller and a good installer for the harmonic balancer, and it is probably a good idea to replace the balancer while you are at it.
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  #5  
Old March 9th, 2018, 10:52
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Ivan Ivan is offline
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A trick I really liked when I went to reinstall the pan, was to use some RTV and install the pan gasket to the bottom of the engine block first.

Apply a thin strip of RTV round the bottom of the block. You don't need ungodly amounts of RTV. Just enough for the gasket to stick to the block. Start from the back around the dip and begin pressing the gasket in place. As you do this, use some of the pan bolts to hold the gasket in place as you work your way towards the front of the engine. Go back and press the gasket in place really well and let it sit for a while. Once the RTV has had a chance to set, you can remove the pan bolts holding the gasket in place, then proceed to install the pan.

I feel it works better than using the zip ties or rubber band trick to hold the gasket to the pan. What worried me about gasket to the oil pan route, was that if the gasket at the rear of the pan dip is not perfectly in place to meet the groove in the rear bearing cap, you're going to wind up with a bigger leak. At least my way you know the gasket is where it is suppose to end up on the block, and the pan will seat it the rest of the way on its own.
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Last edited by Ivan; March 9th, 2018 at 10:56.
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  #6  
Old March 9th, 2018, 19:12
lawsoncl lawsoncl is offline
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Re: Rear main seal + oil pan gasket.

Quote:
Originally Posted by cruiser54 View Post
First thing to do is verify.....

Id be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF...
Amen! First step is feel the back of the block to see if it's oily.
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Old March 9th, 2018, 19:21
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Re: Rear main seal + oil pan gasket.

Quote:
Originally Posted by lawsoncl View Post
Amen! First step is feel the back of the block to see if it's oily.
Yep. It's rarely the rear main seal!!!!!!
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Old March 9th, 2018, 22:49
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4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Re: Rear main seal + oil pan gasket.

201,000

it definitely needs the oil pan gasket,it's pushing out under the timing cover. the valve cover gasket is a couple years old felpro, and has a tiny leak, but definitely isn't the main leak. Maybe it's not tightened right, but that leak is barley damp/ noticeable.


Perhaps the oil filter adapter ( is this a difficult o ring to replace)?

There's so much oil getting on the trany pan and flex plate cover that I can't say it's not the Rms, she's pretty coated underneath. Can you give any links to specific RMS leak photos?


I'll give the undercarriage a wash and see if I can't identify clearer signs of where these leaks are.

Last edited by 4x4JeePmaNthINg; April 21st, 2018 at 04:16.
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  #9  
Old March 9th, 2018, 23:05
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Re: Rear main seal + oil pan gasket.

The oil filter adapter is fun because you don't have adequate clearance for the T60 socket and the head of the ratchet.

An "L" shaped T60 wrench (like an Allen wrench) does fit however. Add a bit of a cheater handle to it and you should be able to break it loose.

Note that there are actually 3 O-rings involved in the oil filter adapter. There is a Mopar set available.
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  #10  
Old March 10th, 2018, 08:21
trippled trippled is offline
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Re: Rear main seal + oil pan gasket.

I usually unbolt the motor mounts and jack the engine up and there's enough room to get my t60 and a 1/2" ratchet in there. Takes .e about 30min at work.

For the rear main I usually slide the top half out a little with a punch and then grab the edge that's coming out with some pliers and pull it out. Going in I dip the whole seal in oil and gently work it back. Couple dabs of anaerobic sealer and good to go. Depending on which gasket you get, the fel pro has some retaining dowels you screw into the bolt holes that retain the gasket for easy install. The Mopar gasket has rubber in 6 holes of the gasket that will hold the bolts in it so you can place the gasket on the pan then push the bolts into the gasket and they'll stay there. Don't forget to add some silicone to the timing cover seams and the rear main seal seal/bearing cap seam.
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  #11  
Old March 10th, 2018, 10:14
JeepNoob JeepNoob is offline
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Re: Rear main seal + oil pan gasket.

When I did the oil filter adapter O rings on mine, I knocked the Torx bit out of a cheap T60 socket. From there, you can slide the box end of a wrench over it. (I used a 6-point 12mm) You'll probably still have to double up the wrenches or use a cheater pipe, but you can do it without having to remove the motor mounts.

You'll need anaerobic sealant for the rear seal and cap. IIRC, you make a "T" on both sides of the cap going from the round metal support in the center of the seal towards the end and then apply it on both of the chamfered edges on the outside.

Make sure you have a 1/2" torque wrench for the cap bolts. Torque spec is 80 ft/lbs. If you have a '96 or later, there will be a main stud girdle that you have to remove. IIRC, this is held in with some of the only SAE fasteners on the vehicle, so be prepared for that.

Make sure the corners of the pan where they go from being straight to curved get a bit of RTV. The Fel Pro gasket works great because it has 4 little pins to hold the gasket and even the oil pan in place while you get some more bolts in. Just put them in hand tight. Having to figure out how to drill and tap them out of a block SUCKS.

It is posssible, but very difficult to remove the oil pan with everything more or less in it's spot. The biggest challenge is the front axle. Some people say that disconnecting the front shocks will allow the axle to drop more giving you more clearance. In my experience, it doesn't work.
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  #12  
Old March 11th, 2018, 09:09
macgyver_7_6 macgyver_7_6 is offline
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Re: Rear main seal + oil pan gasket.

Electrical tape around the punch adds protection from marring the crank.
After boogering up the first rms, I chamferred the rough/sharp edges with a chainsaw sharpening rod...used oil AND dish soap as others have done....and I had to loosen all main caps.

Messy job....get lots of shop towels ready.

Ditto on Fel Pro...the four plastic screw in pins are sweeeeet!
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