How much rear main seal oil loss is considered normal for our cars?

[Nismobishi]

Hello everyone,
I have a 440 that after driving would drip out about a half cup of oil in the garage.

I changed the rear main with a Fel-Pro 2 piece seal and used the blue side seals and used RTV. I followed the instructions on this forum exactly.

Now it is way better but I will still get about a tea spoon full of oil on the garage floor after driving.

Is a tea spoon full of oil acceptable for an old mopar? I would love to have no leak at all but are my expectations too high?

 

[dadsbee]

Are you sure it's actually the seal and not a valve cover or oil gallery plug.

My 383HP was rebuilt back in 1978, it doesn't leak.

 

[Nismobishi]

I'm positive, I have fixed all other leaks and when I take off the inspection cover and look up in there I can see the little drip coming off the rear main seal area.

 

[Jerry Hall]

Here is a pretty good video of rear main seal replacement by Nick's Garage.

 

[BLK 68 R/T]

Could be a leaking camshaft plug.

 

[Nismobishi]

Yep, I studied his videos before I did it. I'm pretty positive it's the seal again as it was leak free for a week afterwords and now it's at a spoon full after sitting in the garage for week.

 

[lewtot184]

i've been thru the valve cover leaking thinking it was the pan or seal a few times.

 

[AR67GTX]

I think most people believe if the rear seal or something drips a drop or two on the ground after a drive, they will declare victory and move on. Getting one completely drip free can be pretty tough. I’ve done everything on my Hemi and can’t find any sign of rear seal leak now but I still get a couple of drops on the cardboard after a drive. I can now find free oil under the rear edge of the left valve cover after I removed it last winter and apparently the gasket I reused didn’t seal up completely again - so it’s a constant battle.

 

[pnora]

A drop is one thing. That spreads to about a quarter or half dollar. A teaspoon can spread to a circle about the size of a 3 pound coffee can or more. Seen too many rear main seals misdiagnosed. A leak never drips from the top.

 

[1967coronet]

If it's making a mess under the car you know it needs fixed.
Couple spots on the floor after a drive and sitting, that comes down to what your willing to put up with.
Hell I drip a couple drops myself but I'm not calling my urologist. I dont really like him that much.

 

[Cranky]

Did you polish off the 'lines' that helped hold a little bit of oil to lubricate the original rope seal? If not, the lip seal is going to leak....

 

[lewtot184]

i don't know how many rear seals i've done thru the years but i can't think of one time i had a leaker. i can't believe that all the rear main leaking problems that folks have or think they have been real. there just can't be this high of a failure rate. i know it wasn't easy for me to figure out the valve cover problems. maybe the easiest and most sure way to figure it all out is with some kind of dye in the oil; then you'd know for sure.

 

[Runcharger]

The vast majority of rear main seal leaks come from sealing the seal retainer to the block.

 

[AR67GTX]

That seemed to be where my former rear main was leaking - the retainer side seals.

 

[RemCharger]

The vast majority of rear main seal leaks come from sealing the seal retainer to the block.

This is my conclusion as well, which is strange because sealing a square aluminum block in a square hole should be the easy part

 

[lewtot184]

i think it has to be back in the early '70's when i first did rear main seals on rebuilds. back then we didn't have rtv's or other good sealers. i don't even remember oiling or soaking the side seals. i didn't have a parts washer or other convenience's, and i sure wasn't a "builder". i just can't remember back then having issues. nowadays i do run a bead of rtv up the outside of the side seal verticals but that's it. this flood of rear main leakers has to have other sources for the oil leak. mopar made millions of these B engines. if there was even a 10% failure rate it would have been a catastrophe.

 

[diesel_lv]

To answer the original question, "no leaks" is normal. My '03 cummins developed a leak, paid 2k in labor for a $5 seal to fix it. My 4.6 DOHC w turbo in my jet boat has no leaks, my '67 383/496 had a rear main leak from machine shop, fixed it. 3 motorcycles, 1 Harley, 1 '79 Suzuki, 1 '08 Kawasaki, no leaks. Leaks are not normal.

 

[70ChargerRT]

Here is a pretty good video of rear main seal replacement by Nick's Garage.

and yet this motor he did still leaked lol.
No leak is acceptable. There’s a few different ways the seals can leak because of clearance problems. Mine was leaking between the seal and the upper retainer I like a fastfish retainer because it has no side seals, notched for ARP Studs and it’s also beveled so you can fill the Edges in. I had to use a rope seal to fix it. It doesn’t leak a drop now.

 

[dadsbee]

i think it has to be back in the early '70's when i first did rear main seals on rebuilds. back then we didn't have rtv's or other good sealers. i don't even remember oiling or soaking the side seals. i didn't have a parts washer or other convenience's, and i sure wasn't a "builder". i just can't remember back then having issues. nowadays i do run a bead of rtv up the outside of the side seal verticals but that's it. this flood of rear main leakers has to have other sources for the oil leak. mopar made millions of these B engines. if there was even a 10% failure rate it would have been a catastrophe.

Would have been a rope seal in the '70's just like my Bees that some 45 years later still doesn't leak. "Newer" technology again proven not to be better...

 

[lewtot184]

Would have been a rope seal in the '70's just like my Bees that some 45 years later still doesn't leak. "Newer" technology again proven not to be better...

i know i didn't use any rope seals. the neoprene seal was the new thing at the time. i had a '68 383 that came with rope but i replaced it with neoprene, maybe 1972 or 1973. i have a june '69 440 block that had a rope seal. i can't remember exactly when we "discovered" the neoprene seal; maybe '71 or '72.