Is there any way to PERMAMENTLY eliminate rear main oil leaks?

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I've used the "Real Gaskets" first hand, so I have DIRECT experience. I was optimistic, given all their marketing talk. Plus, they are very cost effective, so it didn't seem like they were after my money
Disagree on that last point there. You mean "affordable" or "inexpensive". "Cost-effective" doesn't mean the same thing; it means a thing that works well to meet whatever need, at a reasonable cost (lower than other ways of meeting that same need). A thing that doesn't meet the need, or works poorly, cannot be cost-effective even if it costs $0.00.
 
Disagree on that last point there. You mean "affordable" or "inexpensive". "Cost-effective" doesn't mean the same thing; it means a thing that works well to meet whatever need, at a reasonable cost (lower than other ways of meeting that same need). A thing that doesn't meet the need, or works poorly, cannot be cost-effective even if it costs $0.00.
Yeah badly worded. How bout inexpensive?
 
If you do not want your oil pan [ & many otherts ] to leak.........use silicon. The last time I used cork or similar was.....I think...1982...or was it 1983. Silicon has special properties that other gaskets do not have:
- up to 650* working temp
- never goes hard & dries out
- has some elasticity such that it moves with temp changes.
 
If you do not want your oil pan [ & many otherts ] to leak.........use silicon. The last time I used cork or similar was.....I think...1982...or was it 1983. Silicon has special properties that other gaskets do not have:
- up to 650* working temp
- never goes hard & dries out
- has some elasticity such that it moves with temp changes.
The challenge I had was trying to resolve a rear main seal leak. Kept needing to take the pan off so would have cost a lot more (plus time scraping the old gasket material and sealant off) each time I had to do it. Think I pulled the pan like 5 times. The reusable gasket really came in handy.
 
I used both fel pro and that fast fish still leaks not as much as yours but she leaky. Like a Harley marking its territory. Actually my Harley doesn’t leak lol
 
but the OEM factory "rope" seal works well.
I know that is all I'll ever use again. I believe that Mancini has rope seals. The last I got from them WORKED.
Can't say if it's as good as NOS but so far it's good.
Old proverb, It ain't a MOPAR if it don't leak...
 
Well if the seal is installed correctly other issues could be the sealing surface(groove in the crank where seal contacts the crank or the part itself.) If the crank has a groove meaning any imperfection where the seal rides it may be sleeved? I do not know about slant 6 maybe a machine shop guy will chime in ? I do know Ford 5.0 had a sleeve kit years ago for the one piece rear main that always leaked due to a crank groove. Sleeving is just 1 trick that I can think of at the moment. Point is you have to eliminate down to what it is, bad sealing surface, improper install or bad /wrong parts etc. If sleeving is needed but is not an option a new crank may be needed etc. Also think how bad is the leak? is there huge spots under the car? is it needing 1 quart a month during regular driving is it acceptable? etc. I had made mention that 70s cars always leaked once online and some guy chimed in "not any 70s car that I've ever owned" I replied "you musta bought them new?" :lol:
 
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I never had a problem sealing up a slant six. But the only one I had was a 170. Not a drop and I did not use a rope seal, just the standard Fel-Pro rear seal and pan gasket. Of course I do my own work.
 
There's an easy way to stop the rear main from leaking permanently....

Drain the oil.... No oil = no leak...
Years ago, a friend of mine was in a Triumph motorcycle dealership and ask a salesman on the floor how come all these new Triumphs don't leak oil and the salesman told him because they don't have any oil in them.
 
I used both fel pro and that fast fish still leaks not as much as yours but she leaky. Like a Harley marking its territory. Actually my Harley doesn’t leak lol
I buy whatever I can find on eBay for my /6... ROL, Detroit gasket, Victor, etc. I did use the "real" gaskets on the pan and valve cover of which I have 1 each up in the attic still. / Right after I bought those the "real gaskets" company came out with a more expensive line of the same gasket, I remember reading about it but don't remember what the difference was supposed to be. I already had what I do, so I didn't buy their more expensive version.
I do have at least a 1/2 dozen fel pro valve cover gaskets still in their package for a 80-down /6.

I have something to say about some of the fel pro gaskets though.
The ones that are the harder base material with the raised red or blue bands within have bitten me to where I've had to redo them more than once. Especially it seems on a small block or magnum timing cover or plenum plate on the magnums.
I've had to redo more of those than I care to remember, after having used what fel pro offers for these locations.

On one of my Durango's (the one with the 360) I replaced the engine about 60k ago. I got a good used engine for it with less miles. At that time I put it on a stand and completely regasketed it before I put it in. Along with the 1/4" solid aluminum plenum plate available from many places to solve the known problems of sucking oil thru that junction. I used the fel pro with the raised bead. Ever since I did that it's used about a quart every 1200 or so miles. And when I put the gas pedal to the mat sometimes id see a plume of blue smoke while I had it floored. I often buy more than I need "at the moment" from Rock Auto, stock up on parts I might not need today but know that I will definitely need for the vehicles I have as I tend to keep them til they're run into the ground.
Anyway one of the choices they had last time for the plenum plate gaskets were on a clearance and were Victor Reinz. Over the years I've used alot of Victor brand gaskets, I don't know where the "Reinz" part of their name showed up. But I seem to have better luck with their products than current day felt pro products.
I put the Victor Reinz plenum gasket on the Durango last time and finally solved the oil eating problem on that engine. It don't use any oil anymore between changes ... (Which I do around 4k miles)
Different material, it's a thicker, more conventional "gasket paper" material vs the super thin harder material with the raised up beads that felt pro offers for that application.
I have a head swap job and a complete rebuild job in the garage (2 different completely seperate jobs) that among others I will need head gaskets for both. I tripped across a deal on some fel pro Marine grade head gaskets for small block Mopar, that I bought enough for both plus 1 extra set for "just in case" while the gettin was good.
I first seen them on eBay for what seemed like a good deal "according to the gut feel" but there were only 3 available at least from that seller.
For the hell of it I punched that number in at rock auto and behold they had them for a few bucks a gasket less. So I threw 3 more in the cart while I was buying other (crap) from them anyway....well see how those work. I do have some more conventional fel pro head gaskets here that will fit the same engines/ I guess as a plan B.
 
I was so meticulous when putting my engine together, spic n span clean, used anaroebic sealer, RTV, etc., I put mine all together, weeks later, and there it was, a leak in the rear main area. It's difficult to figure out if it's the pan, rear main seal bracket, or rear main seal. Even with the engine on my engine run stand and good light~ just difficult to pinpoint the LEAK, or more like a steady drip in my case. So, one has to address everything all over again. I feel just because a mechanic is experienced, they're human and can mess up as well as any of us.

So, now, I had to work on the engine with dropping the pan, at least on my engine run stand. I despise this design. So, drop the pan, clean up, have new parts on hand, new tube of RTV this time, be careful not to push the rubber gasket(the one on the pan to the rear main seal bracket), I had it all together, then felt around and I had to loosen all the pan bolts, fanigle the rubber gasket back in place! omg. I've ran it for at least an hour overall, and so far ok. (knock on wood!)

this is an older pic, it's complicated, I wound up using a Roll master timing chain, Rusty knows and Zach for sure.




 
I was so meticulous when putting my engine together, spic n span clean, used anaroebic sealer, RTV, etc., I put mine all together, weeks later, and there it was, a leak in the rear main area. It's difficult to figure out if it's the pan, rear main seal bracket, or rear main seal. Even with the engine on my engine run stand and good light~ just difficult to pinpoint the LEAK, or more like a steady drip in my case. So, one has to address everything all over again. I feel just because a mechanic is experienced, they're human and can mess up as well as any of us.

So, now, I had to work on the engine with dropping the pan, at least on my engine run stand. I despise this design. So, drop the pan, clean up, have new parts on hand, new tube of RTV this time, be careful not to push the rubber gasket(the one on the pan to the rear main seal bracket), I had it all together, then felt around and I had to loosen all the pan bolts, fanigle the rubber gasket back in place! omg. I've ran it for at least an hour overall, and so far ok. (knock on wood!)

this is an older pic, it's complicated, I wound up using a Roll master timing chain, Rusty knows and Zach for sure.





I'm going to reseal mine soon and when I do, I'm going to completely eliminate the oil pan gasket and go with all RTV. Probably do the timing cover, too. The pan and block mating surfaces are all smooth and flat, so it will seal like a big dawg. I'll probably replace the seal too while I'm there. I cannot decide which. The one piece seal I'll need to at least loosen all the main caps and pry the crank up....which I'm not afraid of doing, so that might be what I do.
 
Hi Guys/Gals: Cruiser here. I've been enjoying driving my slant six 1974 Duster with its newly rebuilt engine. The motor runs very well, but I just cannot get rid of a persistent rear main oil leak. The shop that rebuilt the engine is very experienced and reputable. They installed a new rear main seal in November of 2024, which failed a month later. On Dec. 12th, they installed a new seal which is now leaking after about 1500 miles. So I'm looking at putting in my third rear main seal in about three months. So what's going on here? Does anyone out there own a slant six that DOESN'T leak oil out of the rear main? Does such an animal even exist? I could really use your advice, especially Slant Six Dan if you're out there. If you did cure your leaky seal, what product did you use and how did you install it. Is there some kind of super duper seal that I need to use this time? My expectation is for the engine to go 100,000 miles without leaking. Your thoughts? What worked for you? Am I nuts to expect the floor under my Duster to be clean and dry?

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PERMANENTLY in capitals in your title is a pretty bold request. :poke: :lol:
 
You slant 6 folks are damn lucky that Ma Mopar put a strong crank in those slant 6's because she sure short changed you on the main bearings. Unbelievable they stand up to any abuse.
 
You slant 6 folks are damn lucky that Ma Mopar put a strong crank in those slant 6's because she sure short changed you on the main bearings. Unbelievable they stand up to any abuse.
Same size mains as a 440,..440÷5=88c.i./main,...225÷4=56.25c.i./main, I think we're good..
 
Same size mains as a 440,..440÷5=88c.i./main,...225÷4=56.25c.i./main, I think we're good..
Bearing size is not my point. Everybody else's straight 6 engines have 7 mains.
 
I'm going to reseal mine soon and when I do, I'm going to completely eliminate the oil pan gasket and go with all RTV. Probably do the timing cover, too. The pan and block mating surfaces are all smooth and flat, so it will seal like a big dawg. I'll probably replace the seal too while I'm there. I cannot decide which. The one piece seal I'll need to at least loosen all the main caps and pry the crank up....which I'm not afraid of doing, so that might be what I do.
I'm not slant 6 savvy. Rope or 2 piece rubber?
 
I'm not slant 6 savvy. Rope or 2 piece rubber?
I guess it depends on the year. They used rope to a certain point, if I am not mistaken and then switched over to the two piece modern seal. Maybe @slantsixdan can enlighten us on that. I think I am going to try one of those one piece seals on it though. They are available for the big block, which is the same seal as the slant 6, so I may try that. I'm not 100% sure my seal is even leaking, but if I pull it back out, it's gettin one. lol
 
i hope my six don't leak ..... sitting on the stand waiting for the cab to get done
so easy test is use a smoke machine on it before you put it in ...
rear main might not show right away ....but i have a rachet pump that i tap into my oil pressure sending unit to prime my engines will show a rear main leak with out installing it in the car
 
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