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Rear main seal parts

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willyt View Drop Down
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    Posted: 15 Nov. 2018 at 9:15pm
After installing a filter on my ‘52 L134 I dropped the oil pan to clean it out. The engine has a small rear main oil leak. I noticed that the ends of the seal plugs are flush with the block and I am under the impression they should extend somewhat from the block. I understand the purpose of the seal that goes around the crank bearing. But what part do the plugs play? Would it be a waste of time to replace only the plugs to see if that cured the oil leak? It looks like the material may be neoprene.
1952 CJ3A (Lil'Green)
early M38A1(Ole Green)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 12:39am
IIRC, They seal between the block & the main bearing cap. They do on the Studebaker Champ engine I am currently rebuilding.

IME, it is a waste of time & energy to try to replace just these strips/plugs. To do that you need to remove the bearing cap. This will disturb the crankshaft seal, which if not replaced, will leak. The strips/plugs should stand just a bit proud of the block, but by less than 1/16". Many mechanics cut them flush with the block & have good luck with them sealing, so to find them flush is not uncommon. Clean the surfaces up well & apply a dab of, either red RTV, or #2 Permatex. If those joint are your problem, this will fix it. 

IHTH, Cpt Logger.
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willyt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote willyt Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 9:20am
ok, I was wondering what part they played in the sealing process. Can't find any cutaway pics.
1952 CJ3A (Lil'Green)
early M38A1(Ole Green)
1970 Jeepster Commando
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Rus Curtis View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rus Curtis Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 10:11am
What I read from the Service manual, Section D, L4-134 Engine, near the end of par D-17, the rear bearing cap packings are supposed to protrude approximately 1/4" and do not trim.  When the oil pan is installed this will compress those packings where they will form the seal.  Yours being flush indicates they've been compressed into the hole. 
 
The Service Manual will really help in nearly every aspect for rebuilding and maintaining.
 
If your rear main is leaking, that seal and the crankcase contact surface will need to be evaluated.
Rus Curtis
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Post Options Post Options   Thanks (0) Thanks(0)   Quote willyt Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 10:40am
Thanks for the info Russ. I have the manual and have read it. I guess I'm one of those pia's who wants to know how things work. I understand how the crank seal works but I'm curious to know what the rods seal. I've never been into these blocks before and am having a hard time visualizing what they do. I notice that some engines, not the L or F  heads, do not use the rods.
1952 CJ3A (Lil'Green)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rus Curtis Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 10:53am
I think I get what you're saying.  To me the SM explained how they work.  There is no sealant or gasket for the rear main cap.  Without the packings, there wouldn't be anything to seal along the sides of the bearing cap.  That would leave only the outside surface where the oil pan makes contact -  and that has sealant on it. 
 
The packings expand and seal without using sealant (which would behave like glue) causing that bearing cap to stick in place.  This WOULD be a PITA.
 
Sometimes owners will add a dab of sealant around the rear main seal ends but that's a different seal.  No sealant should be used on the packings.  Compressing them is how they work - any trimming may cause them to not compress enough to seal.  If you didn't remove the rear bearing cap, the packings should still be sealing leaving you with just the outer surface where your oil pan goes.
 
HTH


Edited by Rus Curtis - 16 Nov. 2018 at 10:55am
Rus Curtis
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Post Options Post Options   Thanks (0) Thanks(0)   Quote willyt Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 11:21am
Hey Rus - thank you very much for the additional information I just like to understand how things work, makes it easier to diagnose problems.
What service manual are you referring to? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rus Curtis Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 11:47am
I have the SM-1002-R6, publ 1965.  I believe it is a combination of multiple SM's.  It covers CJ-2A/CJ-3A/CJ-3B/CJ-5/CJ-6 and DJ-3A models.
 
I don't have access to original factory SMs specifically for the CJ-2A.
 
I did look around a bit (here in the Forum and on the 2A website) but didn't find an image of those packings in place.  Perhaps someone else knows. 
 


Edited by Rus Curtis - 16 Nov. 2018 at 12:21pm
Rus Curtis
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willyt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote willyt Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 1:04pm
I'll look up the manual you mentioned Rus.
 
It sounds like the seal rods are  the last-line of-defense for an oil leak.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 1:20pm
Originally posted by willyt willyt wrote:

I'll look up the manual you mentioned Rus.
 
It sounds like the seal rods are  the last-line of-defense for an oil leak.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote smfulle Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 2:11pm
Here's a picture from the manual. 
You can see where the plugs go in the holes that are formed when the rear main cap is assembled. The cap fits down into the block creating the holes. The rubber plugs fit down into the holes between the cap and  the block. The plugs stick up so that when the oil pan is installed, the pan pressed the end of the plug and expands it in the hole to press against the block side AND the bearing cap side, forming a seal. If you cut them short, they won't get the proper expansion to seal the gap.



Here's a  quote from the manual regarding the plug installation (called "packing" in the manual).

"When installing the rear main bearing cap in the
crankcase, place a small amount of plastic-type
gasket cement on both sides and face of the cap
to prevent oil leakage. Insert the rubber packings
shown in Fig. 60 into the holes between the bearing
cap and the case. Do not trim these packings. The
packings are of a predetermined length that will
cause them to protrude approximately 1/4" [6.4
mm.] from the case. When the oil pan is installed,
it will force them tightly into the holes and effectively
seal any opening between the bearing cap
and the crankcase."
Stan
48 CJ2A (Grampa's Jeep)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote willyt Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov. 2018 at 7:40pm
Stan that picture sure helps me to understand how things work. Thank you for taking the time to hunt down the info and posting it. As they say a picture is worth a thousand words.
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early M38A1(Ole Green)
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