Rear Main Seal Leak?

[EDL]

on a 302 crate engine, i am leaking oil down the front of the transmission when parked -- I have read some other threads saying it could be through bolts on a 302 as they need thread sealer, but I wiped everything down and the snail trail is straight down the front of the tranny

Is there more to do to ensure it is a rear mean seal before diving in to fix?

This is a crate engine new as of 2016 with only 1600 mi on the build ... i have just inherited it so i don't have all the historical info (yet) but the operating assumption is new ford racing crate engine 302/340h in 2016 with 1600 mi as of now

Assuming it is a rear main seal, FMS has said that all blocks of this type (XEFM) have a single piece rear seal ... am i correct that the only way to replace is to remove tranny? suggestions on a replacement seal part #?

Thanks for any guidance...!

[boat737]

Firstly, I would make sure that that is where the leak actually is. There are a few other spots that can leak, and find their way down there.

After my build with a few hundred miles on the motor, I was dripping oil from the bottom of the bell housing. After two weeks of wiping clean and chasing trails, I finally found the leak to be a DS forward valve cover gasket. That leak (on the forward edge of the valve cover) managed to travel almost 3 feet to where the drip was.

[john42]

My 302 main seal was leaking and I spent a bit of time chasing it down. I was getting ready to do a smoke test, but my clutch throw out bearing fried so it all had to be pulled apart anyway. So leaking or not I had the rear main seal replaced as I was 90% confident it was the source of the leak. Since then, no leaks! So in my case I was correct. Smoke test is a good way to know for sure where the leak is.

[EDL]

Thanks B737

Will do that some more ... to be clear, the path is definitely down the front of the tranny .... and starts up at the top of this metal plate (flex plate?) ... see arrow in pic



20221026_105241.jpg






... I guess you are saying more than one leak can end up dripping down that pathway ... understood! Will continue to look

[EDL]

My 302 main seal was leaking and I spent a bit of time chasing it down. I was getting ready to do a smoke test, but my clutch throw out bearing fried so it all had to be pulled apart anyway. So leaking or not I had the rear main seal replaced as I was 90% confident it was the source of the leak. Since then, no leaks! So in my case I was correct. Smoke test is a good way to know for sure where the leak is.

Thanks John

Is a "smoke test" something you can do DYI or do you have to go to a shop?

[john42]

I was going to build my own.

Then there's this guy: https://www.youtube.com/watch?v=PnU-SY6egr4

I find him annoying but he does often have the solution I'm looking for.

[egchewy79]

if it's a one piece seal. you'll have to take out the tranny or pull the motor.
it could also be your flywheel bolts in this location. these typically need to have thread sealer as they do encounter oil.

[Chopper]

It could be rear main, but if your intake manifold or valve covers are leaking a small amount, the oil will be pushed back here and run down in that area. I had a similar leak that was also resolved via tightening the valve cover gaskets. Looked like it was coming from the rear main seal as in your picture, but was just a trickle up above running around and down.

[EDL]

got it guys and thanks

seems like a simple thing to do is to re-torque oil pan, valve covers, [heads?], etc. and see if that eliminates it....sure is a lot easier than taking tranny out!

[EDL]

if it's a one piece seal. you'll have to take out the tranny or pull the motor.
it could also be your flywheel bolts in this location. these typically need to have thread sealer as they do encounter oil.

Thanks ... for threadsealer, something like this? Permatex 59235 High Temperature Thread Sealant

car has a Tremec 5 ...anyone know the torque spec for the flywheel bolts?

[Otee453]

Oil dye and UV light to detect source of leak.
SBF's will commonly leak in various places but look like they are coming from the rear main.

[Avalanche325]

As everyone is stating.....and hoping for you, it might be something easier than the rear main.

It could be the intake manifold. That often needs to be torqued a few times after it heat cycles anyway. Also, sometimes people make the mistake of using the china wall gaskets on non OEM parts. That is at the front and rear of the intake. Guess where an intake leak will end up?

If you do end up replacing the rear main, make sure you pay close attention on if the seal should be lubricated or not. If you don't lubricate a rubber seal, it will leak. If you DO lubricate a Teflon seal, it will leak.

Here is a thread from when i did mine with all the tips and tricks you need to know - https://www.ffcars.com/threads/rear-....510601/page-2

[EDL]

As everyone is stating.....and hoping for you, it might be something easier than the rear main.

It could be the intake manifold. That often needs to be torqued a few times after it heat cycles anyway. Also, sometimes people make the mistake of using the china wall gaskets on non OEM parts. That is at the front and rear of the intake. Guess where an intake leak will end up?

If you do end up replacing the rear main, make sure you pay close attention on if the seal should be lubricated or not. If you don't lubricate a rubber seal, it will leak. If you DO lubricate a Teflon seal, it will leak.

Here is a thread from when i did mine with all the tips and tricks you need to know - https://www.ffcars.com/threads/rear-....510601/page-2

Thanks for this ... PM sent

[cnutting]

To add another experience, I had a couple nagging leaks on my 289. Most were cured when I swapped the pan, but still had one leak thst was similar to what you described. Turned out to not be the rear main seal, but the DS valve cover.

[EDL]

Thanks

Step 1 will be to retorque all involved bolts (oil pan, valve covers, etc.) -- then see if there are still leaks...

[EDL]

...anyone know the torque spec for the flywheel bolts?

answering my own question in case it helps anyone else:

TRANSMISSION
The M-6007-X2303E comes equipped with a 157-tooth manual transmission flywheel.
Sealer is required on the small block flywheel to crankshaft bolts. Torque to 75-85 ft-lb. Over torqueing will distort
rear main seal area and cause leakage.

[EDL]

Speaking of torque values, is there a book/manual/service repair manual call it what you will that walk through how to build/rebuild a ford racing crate engine (in my case an XEFM long block)? I looked up Helms and they only sell it for an entire car and not just for the engine -- Ford small block rebuild books are mostly for classic car ford engines (say up through the 80's) -- Thanks in advance any suggestions!