302 main seal leak

thejoe

Member
Jul 7, 2020
28
6
13
39
Moscow, ID
I've got a leak that's hard to pin down - the drips come off the front of the oil pan, but there is no obvious source other than what looks like a drop of oil coming from the rear main seal (the oil does not fall from the engine to the ground at the rear of the engine, but rather from the front edge of the oil pan). This is in a pre-81 302 with only about 1500 miles on the motor.

At some point, I'll need to replace the rear main, but I want to know if high mileage oil (e.g. valvoline or something like it) might help to slow the slow leak. I'm not familiar with what this oil will do to seals and such - does it cause any premature wear or expansion/contraction issues over time?

Currently it's running Shaeffer's full synthetic, high zinc due to the age of the engine.

I don't race with the car, but do enjoy the occasional 6,000 RPM pull (OK, I do this more than occasionally, to be honest... it sounds so good!).

Joe
 
  • Sponsors(?)


7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
5,589
1,855
194
Kearney, NE
Your current oil is fine. Some seal softener/swelling additive might help slow the leak. But surgery is the best answer.
 

thejoe

Member
Jul 7, 2020
28
6
13
39
Moscow, ID
Schaeffer's is great stuff, from what I read. I can't get any locally, though.

Is it the absolute best oil for an old 302?

Any recommendations on a seal softener?
 

thejoe

Member
Jul 7, 2020
28
6
13
39
Moscow, ID
E54F531D-93B4-462E-B5B8-88CCDBCAAAAB.jpeg

This is how much it leaks, whenever I park it for 8 hours.
 

nickyb

WAIT,you now have a pair?
10 Year Member
Apr 3, 2009
1,101
506
143
59
nevada
That old guy Scotty kilmore on u tube gets some sealer from amazon,just can't recall the name.it's AT 205 reseal.
 
Last edited:
  • Like
Reactions: 1 user

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
5,589
1,855
194
Kearney, NE
Go with a good name brand like Bars Leak. Lucas makes good copies of everything, so that’s another I would consider.
People try bottle remedies before surgeries on themselves, and it might be worth a try here. Just know these will not fix a cracked gasket or seal.
 

65ShelbyClone

Founding Member
Sep 9, 2000
4,657
36
119
Antelope Valley, SoCal
You'll have to pull the transmission, clutch, flywheel, oil pan, and rear main cap in order to replace a two-piece rear main seal. If you can do that at home, then yes it can be done at home.

The "high-mileage" oils aren't going to help IMO.
 
  • Agree
Reactions: 1 user

thejoe

Member
Jul 7, 2020
28
6
13
39
Moscow, ID
Thanks. Everything in that list sounds doable - though I’m not sure about the rear main cap. Do I have to have an engine hoist for that?
 

65ShelbyClone

Founding Member
Sep 9, 2000
4,657
36
119
Antelope Valley, SoCal
Now that I think about it, maybe. The rear of the engine will need to be supported somehow. An engine support bar/leveler would be perfect or you could look at the design and DIY one. I've never had to do a rear main seal with the engine in a car.
 

Mike 66 coupe

New Member
Aug 12, 2020
1
0
1
74
London, Oh.
I've got a leak that's hard to pin down - the drips come off the front of the oil pan, but there is no obvious source other than what looks like a drop of oil coming from the rear main seal (the oil does not fall from the engine to the ground at the rear of the engine, but rather from the front edge of the oil pan). This is in a pre-81 302 with only about 1500 miles on the motor.

At some point, I'll need to replace the rear main, but I want to know if high mileage oil (e.g. valvoline or something like it) might help to slow the slow leak. I'm not familiar with what this oil will do to seals and such - does it cause any premature wear or expansion/contraction issues over time?

Currently it's running Shaeffer's full synthetic, high zinc due to the age of the engine.

I don't race with the car, but do enjoy the occasional 6,000 RPM pull (OK, I do this more than occasionally, to be honest... it sounds so good!).

Joe
You might try a dye in the oil that glows under a black light before you start unbolting stuff. It'll help pin point the source. Probably pick the dye and light up at any auto parts chain store. Good luck.