rear main seal

does replacing the rear main seal on a '88 XJ really fix the leak?

I have not done this but once on a chevy 350. the leak returned in 2 days. Later I found out that the rear main seal usually failed due to another reason (like wobbling crankshaft)

Just wondering who experienced successful repair where the leak did not return?

thanks

well if the rear main seal leaking is the problem, then i sure hope putting a new one in would fix the problem. it's like asking if replacing an alternator when the old one goes bad would fix the problem.

ChipsXJ said:

does replacing the rear main seal on a '88 XJ really fix the leak?

I have not done this but once on a chevy 350. the leak returned in 2 days. Later I found out that the rear main seal usually failed due to another reason (like wobbling crankshaft)

Just wondering who experienced successful repair where the leak did not return?

thanks

Click to expand...

I did mine 4 weeks ago...No leak yet (now I will probably get one :laugh3: )

Make sure you get the One Piece rubber Oil pan gasket, and more then one seal. It was my first one, I used four ooops.

Have fun

Did the rear main on my 88 4.0 2 years ago and still holding up fine. Plenty of basic infoon how to do it. About a 5 on a 1-10 difficulty scale if a first timer. About a 3 if you have done it before.
BSD

Sometimes a seal will not fix the problem as the hard part (crankshaft or whatever) will be scored from a hardened rubber seal riding on it for too long a period of time. In this case a speedi sleeve might be used.

http://www2.chicago-rawhide.com/speedi_sleeves.htm

http://www.acorn-ind.co.uk/products/prspeedi.htm

Jay in MA

I know on my dodges, I have to pull the trans to do the rear main...do I on a 4.0? Thanks

Nope, no need. It is a two piece seal. No special tools beyond maybe a brass punch to drive the old seal out if neded.
BSD

I've done it twice - on an 87 and an 89. That was several years ago, and neither has developed new leaks.

The rear main seal is a semi-rigid two-piece seal, and the "Sneaky Pete" tool that you'd use for SBC/SBF "rope" seals won't work. The brass punch or drift that is used to "pop" the seal out works because the rubber seal has a steel core, and you push on that.

Check your rear main journal when you have everything torn to bits - if there's a groove worn in it (it happens...) you'll want to get the "double-lip" seal from Fel-Pro, so the second lip will ride on a smooth surface and you'll get a good seal. Most of the time, when I've found out about a rear main that didn't fix the leak, that's what it turns out to be.

If you're lifted 3" or more, you can pull the pan with all four feets on the ground. Less than 3" lift, and you should jack the front up so that the front axle hangle in the air a bit, and sits at "full droop." For a stocker, this is MANDATORY. You don't have to unbolt anything - just jack up the front, put stands under the frame rails, and let the axle droop.

Note that a "speedi-sleeve" will probably be a more involved repair than the double-lip seal. I've done a few.

Soaking the new seal in oil (and maybe rubbing the lip a bit with your fingertips!) is a great way to ensure that a pliable seal is installed, and the slight oil permeation on the upper half helps it slip into place using only finger pressure.

You might want to pull a cap or two while you're down there, and visually inspect the bottom end bearings.

5-90

5-90 said:

Check your rear main journal when you have everything torn to bits - if there's a groove worn in it (it happens...) you'll want to get the "double-lip" seal from Fel-Pro, so the second lip will ride on a smooth surface and you'll get a good seal. Most of the time, when I've found out about a rear main that didn't fix the leak, that's what it turns out to be.
5-90

Click to expand...

Before asking I've checked your book and there's no mention of the part number for the double lip seal. Happen to have it handy?

Thanks!

Mental note made...

I don't happen to have my Fel-Pro book handy, or I'd tell you. I was just thinking of that myself...

5-90

I recently thought I had a rear main leak.
Replaced the valve cover gasket, cleaned everything, no more leaks.
I replaced one a few years ago and I seem to remember that installing the seal with the correct side facing forward, was the most important thing along with some anerobic RTV for the flat surfaces of the cup.

Yes, a valve cover can present as a rear main - which is why I tell people with oil leaks behind the distributor to clean the engine THOROUGHLY and recheck - no sense in doing a job you don't have to.

Getting the seal in the right way around is also important - get it in backwards, and it will still leak (because the wiper's facing the wrong way.) It's kinda like putting an axle seal in backwards - the wiper won't work.

I've heard mixed reports on the use of silicone/RTV on the cap and seal ends - I ended up not doing it. One hasn't leaked for six years, the other for four. I'll probably continue not using RTV when I do that job...

5-90

why do they even have an oem style lip? wouldn't you just but athe offset lip one just to be sure? why would one put in the oem style if it might leak due to wear on the crank when the offset lip will go where there is no chance for wear?

Done one in my 84 Eagle and 94 XJ simple job for the person with some basic skills. Neither one has ever leaked. The XJ stock height does require jacking and letting the axle hang. The pan will come out and go in easily. The Eagle was a chore as it was much tighter. It required some disassembly. A touch of RTV on the ends of the seal prevents seepage, Do not apply so much as to have it squeeze out between the block and cap to prevent proper torquing.

I'm gonna need that part number for that double lip seal as well. I replaced it maybe 6 months ago and it's back leaking like crazy.



EDIT:
Actually I just looked up the part number I used when replacing mine. It turns out it was a double lip seal, it was from Advance. Part number BS40612.

Eh well I guess I'll try again and hope I don't have some mega bad rings or something.

funvtec said:

why do they even have an oem style lip? wouldn't you just but athe offset lip one just to be sure? why would one put in the oem style if it might leak due to wear on the crank when the offset lip will go where there is no chance for wear?

Click to expand...

Because, typically, the OEMR seal doesn't wear a groove in the journal.

You see, the OEMR seal is an elastomer ("rubber") that rides on a machine cast iron surface in the constant presence of oil. The seal wears out - which is why it wants to be replaced.

In some cases, there is a small amount of grit that gets trapped under the lip, and isn't flushed out by the oil (which is not under pressure, by the way.) This can result in a "groove" worn into the crank journal, right under the pointed edge of the lip. This is what the "double lip" or "offset lip" is meant to repair.

The old-style "rope" seals have a wider contact patch - a crankshaft groove there usually means a re-crank. There's no easy way to "move" the sealing surface on those.

Since it is typically the "rubber" seal that wears out, replacing the seal will serve nicely. Since the seal is easier and simpler to replace than the crankshaft, it is typically meant as a "sacrificial" part and therefore designed to fail first.

Make sense now? Or should I have another go at explaining engineering decisions (which, often, don't make sense to engineers...)

5-90