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Is my rear main leaking or no ?

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BigRedCornhead View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BigRedCornhead Quote  Post ReplyReply Direct Link To This Post Topic: Is my rear main leaking or no ?
    Posted: Mar/30/2023 at 12:53pm
my money is still on the cam plug, what has everyone used to stop that from occurring, im positive during my rebuild i put something on the threads still weeps a bit?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Candymancan Quote  Post ReplyReply Direct Link To This Post Posted: Mar/27/2023 at 11:54am
Oh i gwt it.  I didnt put enough on for that.  It didnt even squish out.  Thats why i was worried it migjta been the pan ( hense why i smooshed it with a socket exntention and hammer haha..

No i made sure it wouldnt block that drain..  

It didnt even squish out the side of the pan anywhere else either.  The pan must (float) and not be 100% flush to the metal surfaces.  The rear rubber lips pop out way too much too which means it must float in the back si the rtv couldnt actually squish unless you used a BOAT load. Which i didnt exactly do.  I made it asd thick as the rubber would be.  (To fit in the groove and stick out just enough)  it still leaked like this though even with the cork and rubber.  Litterally each time i do this.. it leaks exactly the same as prior its weird.   Its why im wondering if the worn out knurles is the cause.  My crank does have 150k on it.  Theyre still there.. but on some spots they are not as all i see if a smoothed line from the original seal.

In fact i dont think my original seal is original.  Its yellow on the outside which i think is an older style fel pro ?  Which means its done prior even before me maybe

Are there double lips seals like the 4.0s have ?  Or off set seals.

Would a 4.0s seal fit on a 360 ?  They look identical with the tans and everything.  Minus one being double lip (the 4.2 and 4.0) and one being aingle for the 360.

I have a 4.0 seal and it actually even fits in the bearing cap too when i put it in. To test


Edited by Candymancan - Mar/27/2023 at 11:58am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Mar/27/2023 at 10:58am
A long shot but have seen what your describing once on a Jeep. What happened is someone put so much RTV in the rear main seal faces that it came off as a bead and pretty much blocked off the oil return on the back of #5 bearing cap. Enough oil would flow at idle to relieve the back of the bearing, but at higher RPM's the passage was so blocked off that oil just poured out the back of the rear main seal as it had no were else to go.
Just a long shot as stated.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Candymancan Quote  Post ReplyReply Direct Link To This Post Posted: Mar/27/2023 at 2:16am
Question.  The amc crank where the seal rides.  Mine has a polish on it sligjtly where the knurles are those //// lines could this be the reason ?  The knurles are so long too but the seal only sits in the front..  So there must be more to this.

Are there double lip seals or offset seals that would work ?  You know a seal that rides on the fresh knurles and not the one with the groove polished into it ?

Wouldnt the 4.0 or perhaps the chrysler 360 rear main which is douboe lipped fit ?  They do look similar
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buzzman72 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/26/2023 at 1:24pm
A properly operating PCV valve only opens at a "medium" engine vacuum. At low vacuum, the weight of the plunger keeps the plunger on its seat. At high vacuum, the plunger [theoretically] seals against the TOP side of the valve housing.

The cap at the oil filler tube [formerly known as the "breather cap"] allows atmospheric air into the crankcase, but also can vent excessive crankcase pressure to the air filter housing, when operating properly.

If your piston rings [or broken ring lands] are allowing excessive blow-by, and an insufficient amount of the pressure is being released, the crankcase pressure CAN blow oil out the rear main seal. It can also blow out the RTV if it's used on the intake manifold end seals.

Because piston rings have end gaps, no cylinder is going to seal perfectly. So there will always be a percentage of blow-by. It's simply the nature of the beast.

If you're really wanting to do a thorough diagnosis, buy, borrow, or rent a cylinder leakdown gauge. Assuming you have access to a compressed air source, it can show you if a particular cylinder [or several] has/have a blow-by problem. [It will also show leaking valves, but those won't cause excessive crankcase pressure.]

Doing diligent diagnosis can save you from simply throwing parts at a problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jcisworthy Quote  Post ReplyReply Direct Link To This Post Posted: Mar/26/2023 at 11:33am
If it leaks a PCV or hose from the oil filler to air filter will not fix it

I run these engines on the dyno without either hooked up and no leaks unless something is wrong 

Not a bad thing to hook it up but do not expect it to fix the problem

I have seen unused accessory bolt holes leak before. 

There are a couple threaded holes that come close to the outer head bolt and with one factory and one Indy head oil leaked from under the valve cover through the threads and down the engine 

Something to check anyway
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Candymancan Quote  Post ReplyReply Direct Link To This Post Posted: Mar/26/2023 at 10:14am
Nothibg is clogged already checked.. but the oil filler cap has no vacuum line to the air cleaner anymore it just sits open.  Ny thread in 2017 i made asked why ny rear main leaked after i did that.  

Seems my edlebrock air cleaner didnt come with the nipple for the cleaner to hook ul the hose to it so i left it open.

Im going to get one today and a vacuum line for it and see if that doesnt anything.  But its weird.. doesnt the pcv work better at higher rpm ?? So i wonder if no vacuum line to the carb air cleaner, so it can pull air from the oil filler is the cause.   Maybe the open air cap isnt enough ?  I dunno man im just tired of this leak.  

Im not sure.  Just throwing theories out here.  Because i remembered this was the start of the leak when i swapped that stock system out.  But i forgot if it was coincedence, or why i kept the edelbrock air cleaner in if it was or not.  


It isnt the intake or valve covers.  I used a bore scope to look back there.  All i see is a small coolant leak on the drivers side bolt which ive known about.  I did discover two loose transmission bolts back there though.. So loose they worked themselvs out fairly far on top of the back of the engine and the washer wobbles which is weird...

Its easier to test this open oil filler cap theory than dropping the stupid pan a 3rd time.. so i guess well see.. it makes no sense though as wouldnt the pcv be pulling air through it at high rpm ??, its a weird coincidence when it started in 2017 after i just happened to remove the factory air cleaner/oil filler vent tube. and all the vacuum lines to the engine minus the pcv.  And Charcoal canister stuff.

If the pcv pulls air through the oil tube.. why did factory put a vacuun line to the air cleaner ??

I think maybe ill get a new pcv valve.. eveb though mine is super clean and rattles and works.  I can even hear it at idle in the cab rattling


Edited by Candymancan - Mar/26/2023 at 10:31am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Mar/26/2023 at 12:56am
Oil can leak from the intake manifold, run down the backside of the block, and look like a crankshaft seal leak.

It's very difficult to successfully replace the crankshaft seal in-chassis. Oil tends to get where you don't want it and interferes with the sealing. Even a perfect job with the engine on a stand will still leak a drop or two when the engine is shut off. They always leak a little. That bell housing inspection plate is always a little wet. 

All engine gaskets and seals dislike crankcase pressure. Proper working PCV helps. The crankcase should not pressurize unless the oil filler cap that serves for the air inlet for the PCV is clogged. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Candymancan Quote  Post ReplyReply Direct Link To This Post Posted: Mar/26/2023 at 12:41am
Haha.. i jist found an old thread from back in 2017.. where i asked why is my rear main leaking after i removed the factlry air hat and the breather tube from the oil filler neck.

In the thread i said that the leak stopped wheb i put the factory air hat back on..

Bht thats 6 years ago i cant remember if that actually stopped it or not.  Clearly i put the aftermarket eldbrock back on for some reaso ..

Sooo could no vacuum line to the intake hat on the oil filler neck cap be causing the engine to have too much crankcase pressure at high rpm ??
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Candymancan Quote  Post ReplyReply Direct Link To This Post Posted: Mar/25/2023 at 11:38pm
Well bore scope further in i see a line of oil the flex plate is throwing in thr bell housing.. thays why its dripping by the starter plate on the bellhousing...  whats weird is its throwing the oil on the convertor side if the flexplate

Question my pcv valve seems fine it rattles and is clean i put a tube long enough on the intake and breathed in and out.. no clogs there behind the carb

But i removed the factory air hat and put a edlebrock hat and cap on the fill tube.  I sware i remember like 5 years ago when i did that the oil loss got worse.

Could there be too much pressure in the engine?  I heard thr pcv doesnt work with high rpms.  So if my oil fill cap has no air hat to suck air out of it could there be a build up of pressure inside the engine.   ?  

I did rtv this 2nd time around becsuse i wanted to be sire it wasnt a oil pan leak from cork.  Well it clearly isnt that.   The pics i took inside the bellhousing of the flexopate showing a line of oil going up the entire bellhousing inside.  So its flinging oil.  Nothing wrong with rtv on the oil pan besides it being hard to get off .. Clearly it isnt leaking from the pan now that i looked deeper inside.. 

What problems does it cause exactly if done right.  ?  Wheb i first did my rear main 6 years ago the cork was hard as a rock and 70% of the pickup tube was blocked by cork.  So cork can also do what people say rtv does.  Also i made sure it was flat.. ive been working on cars for 20 years im not fully dumb at this lol..  this isnt the first rear main ive done either.. but this amc 360 is a royal pita.. the 360 magnum and 4.0 and 318s ive done never had this issue


Also fyi cork leaks with synthetic oil.  And there is no other gasket but cork with these amc engines.
 
Ill try the seal a 3rd time.. ( ill use SCE not fel pro) i heared SCE is better.  Before i do this do you think adding another breather to the valve covers.  Or a breather line from the oil tube to the air hat.  Would possibly help with any possible pressure im seeing in the engine ?  

 Im almost curious to try this... Cut a hole in the top of the edlebrock air hat and thread a 90 degree angle barbed fitted on it and put a tubed cap back on the oil filler neck.  Or something like this.  Im seriously wondering if this is the issue.   Every engine has this.  And i removed it by just putting a cap on it but no vacuum line



Edited by Candymancan - Mar/26/2023 at 12:01am
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