4.7l HO bad oil leak.....rear main seal?? - JeepForum.com
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Unread 09-09-2012, 12:59 PM   #1
rsmarais
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4.7l HO bad oil leak.....rear main seal??

About four months ago I bought an 02 WJ Overland from a good friend. The Jeep has been well kept however it has an oil leak that almost appears as if it is coming from the rear main seal. The leak is quite bad and leaks onto the exhaust. The previous owner had already changed the main seal twice and the leak remains leaving me hesitant to go through all the work of changing the seal again without first making sure that it is definitely the problem.

The oil runs down the right hand side, inside the bell housing. It almost appears as if it is coming from around the starter. There is no oil on the left hand bottom end of the bell housing if you know what I mean i.e. it does not appear if whatever is leaking is center as the main seal is.

I have changed valve cover gaskets as there was some oil sweat around but made no difference. The leak is quite bad...so much that it has a continuous fast drip when driving causing the oil burning on the exhaust to cause quite a bit of smoke when pulling up to traffic lights or a stop.

The top of the engine is dry so I doubt the oil comes from the top of the engine.

Is there any other place that the oil could be coming from?

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Unread 09-09-2012, 01:35 PM   #2
billzcat1
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There are PCV breather tubes that run behind both of the heads, then come up to the oil filler neck. Check that both of the breather tubes are intact.
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Unread 09-09-2012, 01:46 PM   #3
rsmarais
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Quote:
Originally Posted by billzcat1 View Post
There are PCV breather tubes that run behind both of the heads, then come up to the oil filler neck. Check that both of the breather tubes are intact.
Thanks for the suggestion. I suspected this though and changed the pipes. Its bone dry around the pipe and fitting.

I see the crank position sensor sits above the starter. If the crankshaft position sensor leaked would/could the oil run into the bell housing?
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Unread 09-09-2012, 03:25 PM   #4
billzcat1
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It could. But really the #1 suspect is the rear main. It's possible that the crank itself is scored where the seal rides and the rear main will just never seal in that position.

Here's an example:


Oil (especially dino-oil) cokes and leaves deposits on the rubber seal surface. The carbon it leaves is harder than the crank which slowly wears a groove into the steel. Eventually, the seal can't maintain tension against the crank, even when brand new. Hopefully this isn't the case.

PS: I have a good friend from Gauteng. Hope all is well in SA!
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Unread 09-10-2012, 12:21 AM   #5
rsmarais
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I really hope that is not the case. It still has low mileage @100 000 miles or 160 000 km. I suppose there is only one wway to find out

Can't complain. We're just moving into summer now so the air is fresh and spirits are high!!

Last edited by rsmarais; 09-10-2012 at 12:23 AM.. Reason: quote
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Unread 09-10-2012, 10:32 AM   #6
rsmarais
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Im hoping someone replies with " oh yes this is a common problem. Just change the crank position sensor o-ring and all you problems will be over"
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Unread 09-10-2012, 05:54 PM   #7
coopdc78
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If im not mistaken..don't they make offset rear main seals for just this reason..I may have to double check..but I think my friend did ..
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Unread 09-11-2012, 01:51 AM   #8
rsmarais
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Quote:
Originally Posted by coopdc78
If im not mistaken..don't they make offset rear main seals for just this reason..I may have to double check..but I think my friend did ..
Could you elaborate a bit? Not sure In following..... Do they make offset seals to not seat on the groove?
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Unread 09-11-2012, 04:44 AM   #9
coopdc78
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It offsets so that where the seal meets the crank is not on the warn part of the crank.thus giving u a good seal and no leak
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Unread 09-11-2012, 08:18 AM   #10
rsmarais
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That sounds good. Do you maybe have a brand or a part number or something that I can research?

Thanks
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Unread 09-11-2012, 08:25 AM   #11
coopdc78
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I believe felpro does. Just look up felpro off set rear main speak. I did not get a chance to dig into it yesterday
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Unread 09-11-2012, 01:30 PM   #12
rsmarais
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Ok so I can honeslty say that Ive googled felpro offset seals wj grand cherokee 4.7 v8 to death and cant find anything for the 4.7

I see for other Jeeps but none form the wj. Can anyone assist with more details. Rockauto has a felpro seal but it does not say if its an offset seal.
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Unread 09-11-2012, 06:15 PM   #13
coopdc78
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I'm not sure why but all I can find is offset front crank seal for the 4.7.. I'm still looking
.I'm 90 % sure the make it...
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Unread 09-26-2012, 11:36 AM   #14
rsmarais
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So surprise surprise! I removed the transmission and found the rear main seal as the culprit. I sourced an SKF speedi sleeve and a new slightly bigger 12mm seal. Never again will I have a leaky rear main seal....on this Jeep anyway.

The removal of the transmission was also quite easy (4x4) Really not as bad as it look at a glance.
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Unread 09-26-2012, 05:09 PM   #15
kfxnando
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hope its fixed!!

however, self have built a few motors and all my motors leaked a little on the seals!! was missing a small trick that when I built my last motor I used and on a motor that is prone to oil leaks, does not leak oil!!

on the crank where it runs on the seal, ruffen it up with some sand paper
so it will be all polished from the seal running of the crank, use some sandpaper to make it dull
the problem/difficulty comes with doing it with the crank still in the vehicle and preventing things from falling inside the motor!!

then when fitting the new seal, put some grease on the seal to prevent it from running dry when starting up

hope this helps

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