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Rear main seal install instructions?

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,354
I dug all through YouTube for links on installing the 2 piece rear main seal on a 302. All I can find is instructions for one piece seals that you find in the more modern motors.

Anyone have YouTube or web links that they could share?

Thank you!

BR
 

1strodeo

Squirrel Watcher
Joined
Sep 15, 2016
Messages
3,596
Loc.
Wisconsin
to accompany all the excellent advice above, here is an excerpt from my old Chilton's book...this is VERY high on my to-do list
 

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rjrobin2002

Contributor
Bronco Guru
Joined
Oct 13, 2007
Messages
2,662
Dont replace it, it will just leak when your done.

I have done 3 and the Broncos still leaked afterwards. That's my pesimistic opinion. I read all the advice, bought the special anearobic gasket material for the rear bearing cap, put thread sealer on the flywheel bolts, did a dab of it at the 2 piece mating surface, and offset it a 1/4" on all 3.

In my first bronco with a new engine the original rear seal leaked that was built by a very good shop. Then i did the rear seal twice with no success. Then the guy that bought it did it twice and he was a very good mechanic and it still leaked, LOL.

Then I had a unsuccessful attempt at a 30 yr old 302 in a used bronco.
 

tirewater

Contributor
Sr. Member
Joined
Jan 28, 2011
Messages
1,040
Loc.
San Francisco Bay Area
I was able to replace mine successfully. However, replacing the seal while on your back getting dripped on by oil - doesn't give you a lot of warm fuzzies about the success of the operation. I definitely had low expectations despite taking my time and being careful.

If you have a minor leak, I'd leave it alone. My seal had a torn lip, so it was leaking quite a bit.

Dont replace it, it will just leak when your done.

I have done 3 and the Broncos still leaked afterwards. That's my pesimistic opinion. I read all the advice, bought the special anearobic gasket material for the rear bearing cap, put thread sealer on the flywheel bolts, did a dab of it at the 2 piece mating surface, and offset it a 1/4" on all 3.

In my first bronco with a new engine the original rear seal leaked that was built by a very good shop. Then i did the rear seal twice with no success. Then the guy that bought it did it twice and he was a very good mechanic and it still leaked, LOL.

Then I had a unsuccessful attempt at a 30 yr old 302 in a used bronco.
 

blubuckaroo

Grease Monkey
Joined
Jun 11, 2007
Messages
11,795
Loc.
Ridgefield WA
I've replaced these seals a lot and have never had them continue to leak.
The main reason I've seen for the leak is the improper application of anaerobic sealant to the end cap.
The surfaces need to be oil free. I mean really clean, in order for the sealant to attach to the block and bearing cap.
If this gap isn't sealed, the oil will ooze through this gap and drip.
 

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Banjer Picker

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,354
I've replaced these seals a lot and have never had them continue to leak.
The main reason I've seen for the leak is the improper application of anaerobic sealant to the end cap.
The surfaces need to be oil free. I mean really clean, in order for the sealant to attach to the block and bearing cap.
If this gap isn't sealed, the oil will ooze through this gap and drip.

Thanks for all of the feedback.

Regarding the anaerobic sealer: how thick/thin should it be applied?

For the seal on the top half (engine block side) how do you prevent the anaerobic sealer from scraping off as you slide the seal into place?
 
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Banjer Picker

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,354
Thanks for all of the feedback.

Regarding the anaerobic sealer: how thick/thin should it be applied?

For the seal on the top half (engine block side) how do you prevent the anaerobic sealer from scraping off as you slide the seal into place?

I reread the directions and see that the sealer actually only goes on the ends.

Still unsure how much to use tho.
 
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Banjer Picker

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,354
Thank you

Thank you for all of the feedback. Wrapped up the new seal install yesterday, still have to install new clutch parts and drip the motor back into the bronco.

I’ll send an updat once everything is up and running to see if it was a success or not. My main concern is whether I went too light on the anaerobic sealer. I put it in the right spot but I went lighter on the amount than I would for standard gaskets.

Any body know the torque specs on the flywheel bolts? The big bronco forum said 75-80ft lbs.

I assume I should use Loktite on the threads right?
 

1strodeo

Squirrel Watcher
Joined
Sep 15, 2016
Messages
3,596
Loc.
Wisconsin
flywheel to crank 75-85 ft lbs

did my install yesterday, shaved about an inch off of the seal during install so may leak again %) but whoever did the last rear main did not remove the pin in the cap before installing the rubber seal, and both top and bottom seals were even with cap/block, so one or both of those were likely the reason for my heavy leak...have yet to run it
 

rmk57

Sr. Member
Joined
Feb 24, 2016
Messages
580
There is a seal crush tolerance that could also cause leaking rear main seals, especially if your engine has aver been rebuilt.

I've had the same issue on a 460 Ford that was distorting the seal causing it to leak. Not sure of the specs on a small block but BBF calls for around .010-.015 for a total of .020-.030 crush.

good luck.
 
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Banjer Picker

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,354
Any final outcome on this?

Hey BB-Roo!

Seal is installed but I still have to re install the motor before I can tell it f it was a success or not.

Tomorrow’s to-do list is:
- Install pilot bearing
- throw out bearing
- Install clutch
- re install motor

Will still be a few weeks before I get to crank it back up but I’ll definitely provide an update...good or bad!

Thanks for checking in.
 
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