Engine New Rear Main Seal leaks

Mystang66

Member
Jul 23, 2011
74
16
19
Minneapolis, MN
Just got my 1985 302 HO back running after pulling the tranny to replace the rear main seal Fel Pro seal BS40620 and repair sleeve 16250. The first time I start it and it’s leaking worse than before the repair. Any thoughts? If I have to go through all of this again, I want to make sure it’s right.
 
  • Sponsors(?)


StangNet created a new car social app called knowmoto! Add your Mustang or post a photo in the knowmoto app and enter for a chance at a $100 gift card from LMR. Click the LMR Logo for more about the knowmoto Mega Thread!

nickyb

WAIT,you now have a pair?
10 Year Member
Apr 3, 2009
1,008
449
113
58
nevada
No not thread locker, sealer. The crank bolt holes go threw and need to be sealed,ask me how I know.
 

Attachments

  • IMG_20200923_171703.jpg
    IMG_20200923_171703.jpg
    745.3 KB · Views: 52

nickyb

WAIT,you now have a pair?
10 Year Member
Apr 3, 2009
1,008
449
113
58
nevada
My first time I did the same, and you see where that got me. I was to lazy to do it over and drove 100,000 miles before replacing the clutch again and then I did it right.
 

Specracer

Member
Nov 24, 2020
38
16
18
51
SE MA
This thread scares me. Did the same thing, but I did 3 things differently, Ford seal, Wurth gray RTV on flywheel bolts, and loctite under the repair sleeve. I still have not yet started the car (I had engine out, slowly getting things back together). Did smoke the engine, looking for leaks, did not seem to be any from the rear main. Fingers crossed.
 

SLOWBRA

Founding Member
Oct 30, 2001
292
2
18
NC
This thread scares me. Did the same thing, but I did 3 things differently, Ford seal, Wurth gray RTV on flywheel bolts, and loctite under the repair sleeve. I still have not yet started the car (I had engine out, slowly getting things back together). Did smoke the engine, looking for leaks, did not seem to be any from the rear main. Fingers crossed.
I feel you. I will be going down this journey myself soon and have always understood that "rear mains will always leak".. lol. Every 5.0/5.8 I've had leaked. Would be nice to find a solution that gives us our best chance.
 

Potomus Pete

Gretchen Whitmer is eating at me
Mar 7, 2019
2,175
768
133
57
Sarasota Florida
Me too I replaced my seal with a new clutch. Started dripping right away. I need a sleeve, and would like some reviews on how some of your repairs
 

91GTstroked

Active Member
Jun 14, 2007
275
83
38
I'm subbing. I plan on replacing my leaky rear main seal along with a new clutch. Do you guys have part numbers for what you used?

There should be a write up on this with detailed pictures if there is a solution.
 

Specracer

Member
Nov 24, 2020
38
16
18
51
SE MA
I feel you. I will be going down this journey myself soon and have always understood that "rear mains will always leak".. lol. Every 5.0/5.8 I've had leaked. Would be nice to find a solution that gives us our best chance.
Im only a few days from starting it, I hope. The crank was perfect, car only has 8k miles, but used the sleeve anyway.

BTW how are the 00R tanks coming along (yes Im the same guy that has been asking elsewhere, ha ha)?
 

Potomus Pete

Gretchen Whitmer is eating at me
Mar 7, 2019
2,175
768
133
57
Sarasota Florida
I'm subbing. I plan on replacing my leaky rear main seal along with a new clutch. Do you guys have part numbers for what you used?

There should be a write up on this with detailed pictures if there is a solution.
Your right , thats why we are waiting on you guys. Can't wait to see them.
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
36,174
12,091
224
Massachusetts
I thought I had the part numbers in my progress thread, but I looked it up.

for the rear main, there are a few. Pull up Rockauto and there are 10 or so to pick from. The Ford one is M-6701-B302.

install varies. I rear that the PTFE ones should be installed dry, and not with a sleeve. So if you run a sleeve you may want to get the rubber one.

I used the fel pro sleeve. I think it’s Felpro 16250 and their install tool. The tool is listed on the package for the sleeve, so I don’t recall what it is now.

as to why I sleeved it? Well this was how my 100k mile crank looked. You can see the groove, but really can’t feel it. I did a RMS 3k miles ago and it leaked. This time around I inspected closer and saw the groove. Hope the sleeve and new seal work

picture looks way worse than it was. There was nothing you could feel with finger.
102F343A-25CF-4C2C-8EBB-50137DA71B9F.jpeg
 
Last edited:
  • Like
Reactions: 1 users

SLOWBRA

Founding Member
Oct 30, 2001
292
2
18
NC
Im only a few days from starting it, I hope. The crank was perfect, car only has 8k miles, but used the sleeve anyway.

BTW how are the 00R tanks coming along (yes Im the same guy that has been asking elsewhere, ha ha)?

If you succesfully resolve the leak please do a write up of exactly what you used/did please. Too many posts with "I think I did this, I believe the part number is this" lol. We need confidence and specifics :)

No tank updates are expected for many months unfortunately. It's been a mess between COVID delays, NASCAR priorities and now the fabricator has a family member ill. They are legitimate reasons for a delay, but it still sucks.
 

Potomus Pete

Gretchen Whitmer is eating at me
Mar 7, 2019
2,175
768
133
57
Sarasota Florida
You need to get the skew number off his plumbing device. He will chime in he must of got it at Home Depot. Just for the record. When I changed my clutch I put on a Felpro teflon seal , and the sob leaked right away. Now, besides my clutch slipping and my car smelling with oil on the exhaust. I need to do this sooner, or later.