replace real seal: how?

[mhead]

Hi All,

My '92 XJ 4.0 I-6 Auto trany has oil dripping off the back of the engine oil pan and off the transmission bell housing. It is not coming from the drain plug seal, but comes from higher up on the motor. Looks like the rear crank seal is leaking.

What do I have to do to replace the seal? I've figured out that I have to remove the oil pan. Can I replace the seal without pulling the motor out? Do I have to loosen the crank bearing caps? I guess (hope) the seal is a two-part and I'll have to poke the upper part out.

Maybe I'll take a few pics and do a tech write-up when I get into this repair...

Mike

[IntrepidXJ]

http://www.jeepin.com/features/rearmain/index.asp

[mhead]

The www site is just what I'm looking for. Thanks, it will really help.

Mike

[Yucca-Man]

Make sure it's not coming from the rear of the valve cover or even from the oil filter housing blowing back along the side of the pan.

[mhead]

I wiped the motor down, then drove it a day or so, then checked again. Looks like the rear seal.

You're right... sometimes it is hard to tell where the leak is since the oil can blow around or come from higher up where you can't see it.

Thanks!
Mike

[ABQ_XJ]

Did you get it done? Just curious since I just did mine. Don't know which RTV is the best to use though, so the pan had to come off twice. PITA

[mhead]

Nope, haven't managed to find the time for the job. You say you took the pan off twice. Was this because of the RTV? I assume you mean that you used RTV on the pan gasket. You must have removed the pan twice for a reason. What was it...?

Thanks!
Mike

[ABQ_XJ]

Yeah it was because of the RTV (2B), used the wrong stuff to coat the rubber gasket and it didn't adhere. A friend at the dealership brought over some Ultra Grey which is what they use. Worked like a charm 2nd time around. The 2B is good for the rear main seal tabs but use the Blue or Grey for your pan gasket.

[91xjtim]

I was under the impression the 1 piece rubber pan gasket didnt need any rtv? Am I wrong?

[ABQ_XJ]

The gasket is made of RTV with metal reinforcement but coating it helps to keep it in place while you juggle the pan into position.

[OT]

for a quick check/ fix pull off the pcv elbow and check to see if it's clogged. you'll notice there's a small hole. If you open the hole up with a larger sized drill bit it'll move more air and relieve the crankcase of excessive pressure which is probably whats pushing oil past the seal in the first place.Too much piston ring blow-by and you'll think you have a bad seal. Just my .02, but this was the problem with my 88 and 92 xjs.:D
If this doesn't work, try upgrading to larger vacuum hoses, or do it all at once and be done with it.:)

[JEONLYEP]

Originally posted by rockcralwinxj
for a quick check/ fix pull off the pcv elbow and check to see if it's clogged. you'll notice there's a small hole. If you open the hole up with a larger sized drill bit it'll move more air and relieve the crankcase of excessive pressure which is probably whats pushing oil past the seal in the first place.

I'll check that on mine if someone could help point me in the right direction. (new to working on jeeps (two extra wheels from what I really know about))

91 4.0

Thanks.

[OT]

I'll check that on mine if someone could help point me in the right direction.

Pcv is located on top of the valve cover. Fresh air is pulled, with engine vacuum, from the breather box into the top front of the valve cover through the elbow. The pcv vacuum hose comes out of the top rear of the valve cover and goes into the intake manifold (the big aluminum thingy that the throttle body sits atop). This is the elbow wherein the hole that needs to be enlarged lies. And this is the vacuum hose that should be replaced with a larger diameter one. By the way, the fitting that the vacuum hose connects to the intake with should also be replaced with a larger one.

[JEONLYEP]

rockcralwinxj

Thanks for the advise.

[mhead]

Originally posted by rockcralwinxj
for a quick check/ fix pull off the pcv elbow and check to see if it's clogged. you'll notice there's a small hole. If you open the hole up with a larger sized drill bit it'll move more air and relieve the crankcase of excessive pressure which is probably whats pushing oil past the seal in the first place.Too much piston ring blow-by and you'll think you have a bad seal. Just my .02, but this was the problem with my 88 and 92 xjs.:D
If this doesn't work, try upgrading to larger vacuum hoses, or do it all at once and be done with it.:)

Wow! never thought about why the oil passes the seal... I was sorta wondering why the air cleaner element was clean on a motor with 175 K. I bet the motor has blow-by and the vent is plugged. Will check and report...

Thanks!

[wim hoppenbrouwers]

Originally posted by rockcralwinxj
for a quick check/ fix pull off the pcv elbow and check to see if it's clogged. you'll notice there's a small hole. If you open the hole up with a larger sized drill bit it'll move more air and relieve the crankcase of excessive pressure which is probably whats pushing oil past the seal in the first place.Too much piston ring blow-by and you'll think you have a bad seal. Just my .02, but this was the problem with my 88 and 92 xjs.:D
If this doesn't work, try upgrading to larger vacuum hoses, or do it all at once and be done with it.:)

[wim hoppenbrouwers]

hello,
My XJ 92 4l 130000 miles is leaking oil from the rear main seal
I am using W10/40 halfsynt.
Overheating is solved by new rad.
Oilleaking was realy alot after a long trip (4 inch stain)
I changed now the PCV connectingtube from rockerarmc tointakeman incl fitting from 1/8 into 5/16 fuelhose and it works!
Leak is only a few drops. In my PVC system was no calibrated orifice.
Question: was it the right way to solve my problem? What about idling or air/fuel mix.?
Greetings from a loonly Jeeper in Holland Europe.

[mhead]

Originally posted by rockcralwinxj
I'll check that on mine if someone could help point me in the right direction.

Pcv is located on top of the valve cover. Fresh air is pulled, with engine vacuum, from the breather box into the top front of the valve cover through the elbow. The pcv vacuum hose comes out of the top rear of the valve cover and goes into the intake manifold (the big aluminum thingy that the throttle body sits atop). This is the elbow wherein the hole that needs to be enlarged lies. And this is the vacuum hose that should be replaced with a larger diameter one. By the way, the fitting that the vacuum hose connects to the intake with should also be replaced with a larger one.

Haven't managed to do much wrenching... but have been doing a little thinking about the real seal leak. Ok, the idea so far from previous posts is that pressure within the pan builds up above atmospheric to the point where it pushes oil past the rear seal. I'm assuming that the pressure within the pan is equal to the pressure within the valve rocker cover since there are many connections between the pan and rocker cover (?). So the pressure within the rocker cover is above atmospheric. It is suggested by previous posts that this happens when the PCV system fails to suck out blow-by as fast as the motor creates it. So far things make sense.

But here's my problem: the PCV system works by drawing fresh air from the filtered side of the intake manifold air cleaner (black box in engine compartment on driver's side front). Pressure at this point is somewhat below atmospheric due to the intake manifold drawing air past the cleaner element. If rocker cover pressure builds to above this, then there is flow of blow-by the wrong way through the feeder tube and into the air cleaner. This is the source of the blow-by oil often complained about in the air cleaner element. The point is that this large passageway should regulate engine internal pressure to just slightly less than atmospheric, leaving no positive pressure to push oil past the rear seal in the pan. See any places I've made a mistake?

Anyway, so much for thinking about it. I've been wrong lots of times so I'm definitely cleaning out the PCV system ASAP.

Mike

[pancake]

I'll be doing my rear main this weekend...maybe I should consider a new oil pump, although mine has no issues. :confused:

[OT]

If rocker cover pressure builds to above this, then there is flow of blow-by the wrong way through the feeder tube and into the air cleaner. This is the source of the blow-by oil often complained about in the air cleaner element. The point is that this large passageway should regulate engine internal pressure to just slightly less than atmospheric, leaving no positive pressure to push oil past the rear seal in the pan. See any places I've made a mistake?

The point is right on. The problem, however, is in the vacuum fitting and hose becoming to restrictive, because of either gunk buildup or excessive piston blow-by. When this happens the crankcase gases have nowhere to go except through the path of least resistance, the rear main seal or the air box. But, when the fresh air fitting of the pvc system get clogged up it'll go mainly through the rear main seal.:D

Question: was it the right way to solve my problem? What about idling or air/fuel mix.?

The best way to fix the problem would be to rebuild the engine so there's not so much piston blow-by. This little fix will just let you get by another 100,000 miles:D .

[Mich88XJ]

Man, I am going to try this tomorrow, if it works, you are a lifesaver, and I really owe you! I hope it works.

[ABQ_XJ]

So what parts do you use to fit bigger vac. tubing? Do you use the same PVC and mod it after the elbow. I opened up the bottom of it some and it seemed to help but still clueless about the rest.

[ABQ_XJ]

Pulled the CCV tube off and found a rubber cap in there plugging the vac. tube. :confused: So this is what's been causing my rear-main leak and oil in the air filter, sunnuva :mad: I suppose I should feel good about replacing the rear main seal last week and all the fun that was. But nice info. rockcralwinxj, it's all good now.

[OT]

So what parts do you use to fit bigger vac. tubing? Do you use the same PVC and mod it after the elbow.

If I remember correctly You'll need to pull the rubber boots off of both pcv elbows. Then just replace with the tubing thats the same size as the elbow like this:

http://www.imagestation.com/picture/sraid82/p7cea798060434ba2e369f1bd40c66306/faee79a3.jpg

http://www.imagestation.com/picture/sraid82/padd625ee4db09299994c4bc6f64df481/faee79b1.jpg

[mhead]

Wow, now that's what I call a bigger vac tube!! There is a metering orifice at the point where the PCV tube connects with the valve rocker cover. Did you remove this? If so, it appears that you've plumbed a big intake manifold leak. How does she idle?

[OT]

it appears that you've plumbed a big intake manifold leak. How does she idle?
What I've done is basically use the tube that fits the elbows. If you look closely right under the throttle body wiring I've simply cut the original vacuum tube shorter and "plugged" it into the bigger tubing. It may seem like I've defeated the purpose of the bigger tubing but, I've also drilled out the oriface in the elbows. My main concern was to decrese all restrictions up to the point were the vacuum tubes meet. Altogether, it has worked. And by the way. I used clear tubing so I can monitor air flow direction at different throttle speeds from under the hood and to see if it's moving any oil.:)
Oh yeah, she idles like she's supposed to because the vacuum fitting in the intake was never enlarged. Only the upstream restrictions were lessened.:)