Rear main seal leak beginning

[dakonthemountain]

Hey Guys,
I am going to be posting a number of questions about Burt about work that I am going to be doing in the coming months. First, he has developed a very small leak at his rear main seal. I will replace it in the not too distant future, but in the meantime I have been told that *maybe* by switching out the regular 10-30 oil to a heavy racing oil it might help stop it, at least temporarily?... anyone try this or know? I really hate leaks!
Thanks!
Dak

 

[LEB Ben]

Dak...I have a small leak coming from the rear main on the Bronco...switching to a heavier oil will help some, but there was still some leaking. What I found that really works is Rear Main Stop Leak...I believe it's produced by Bar's. I was walking through O'Reilly's one day and noticed it and I figured for $4-5 it was worth a shot. I put it in...it stopped the leak completely in 15 mile round trip. As a matter of fact, I swapped the oil in the Bronco last week, noticed it was leaking again, bought a bottle of the stuff, and the leak was gone by the time I got home after I put it in at the store...about 10 miles. I'd look into the stop leak...it won't hurt anything, and maybe bump up 10w40, but make sure it's not a synthetic.

 

[1985 Ford F-150]

I been meanin to see if that stuff realy works. I put some of that stuff that seals up rings in my 390 and it worked for a little bit till it burned it all out. Its this SUPER THICK stuff that helps to seal the rings in old motors I cant remember the name of it.

 

[Skandocious]

Dak...I have a small leak coming from the rear main on the Bronco...switching to a heavier oil will help some, but there was still some leaking. What I found that really works is Rear Main Stop Leak...I believe it's produced by Bar's. I was walking through O'Reilly's one day and noticed it and I figured for $4-5 it was worth a shot. I put it in...it stopped the leak completely in 15 mile round trip. As a matter of fact, I swapped the oil in the Bronco last week, noticed it was leaking again, bought a bottle of the stuff, and the leak was gone by the time I got home after I put it in at the store...about 10 miles. I'd look into the stop leak...it won't hurt anything, and maybe bump up 10w40, but make sure it's not a synthetic.

AHHHH!!!! I would NOT use those products if someone put a GUN to my head... Just think-- if it's powerful enough to gum up the leak at the rear main, ain't it gonna gum up the other oil passages in your motor? Or maybe it has some sort of magical "rear main seal" sensing chemical that makes it ONLY gum up the rear main Nahhh-- I'd advise against products like that.

And Dak-- you can switch to a heavier oil to try and slow it down but please keep in mind the impact that it'll have on the REST of your motor. I'd run only what is recommended by the manufacturer, + or - a little viscosity based on your location (ambient temperature throughout the year). Mine has been leaking 1-2 drops everytime I park since I bought the truck-- has never gotten better or worse. It's just a matter of when I feel like pulling my transmission to fix it.

 

[tomtoc]

AHHHH!!!! I would NOT use those products if someone put a GUN to my head... Just think-- if it's powerful enough to gum up the leak at the rear main, ain't it gonna gum up the other oil passages in your motor? Or maybe it has some sort of magical "rear main seal" sensing chemical that makes it ONLY gum up the rear main Nahhh-- I'd advise against products like that.

pretty much what i was thinking. but... if it locked up other stuff, how could the company be in business.

 

[1985 Ford F-150]

Stuff like that usually has enough liquidity to flow through your oil galleries. Its even more so when the motor gets hot. When I put that stuff in my truck it only bumped the oil pressure up 5 or 10 psi when it was cold. Once it warmed up I couldnt tell the difference.

 

[dakonthemountain]

Thanks guys for the quick response.. I 'll take this all to heart.. A lot of it makes sense. I do think I'll bump up the oil to at least 10-40 though as Ben suggested. Don't see that hurting much.
Thanks again!
Best,
Dak

 

[Skandocious]

pretty much what i was thinking. but... if it locked up other stuff, how could the company be in business.

I'm sure they have a disclaimer on the can that says something like "Use at your own risk. [company name] is not responsible for damage to your engine parts."

 

[1985 Ford F-150]

It just says to not over fill it most of the bottles are a quart so if it takes 6 quarts normally then just put five in and then the leak stop.

 

[LEB Ben]

I'm not saying the stuff is a God send, but I'll use it if it works, and it's working so far. I wouldn't advise it on fresh engine, but hey I'm sure in my 30 year old engine, there has been far worse done to it. The stuff I use is no thicker than Lucas additive. I don't think it actually gums anything up, but causes seals and gaskets to swell.

 

[dakonthemountain]

Isn't the rear main an all metal two piece seal?
Dak

 

[1985 Ford F-150]

Does yours have an FE?

 

[LEB Ben]

Isn't the rear main an all metal two piece seal?
Dak

I thought it was a silicone/rubber type mold.

Does yours have an FE?

It's a '77 so I'm assuming it's a 351/400

 

[dakonthemountain]

No, Ive got the original 460.... stickers, matching numbers and all. Isn't that a 385 series?..

 

[Skandocious]

I thought it was a silicone/rubber type mold.

On my engine-- you're correct. It is usually made out of rubber or teflon. The one I bought on summit (and haven't installed yet) is made out of "Fluoroelastomer"... Whatever the hell THAT is...

I'm assuming your engine is pretty similar.

 

[dakonthemountain]

I seem to recall reading about it in my shop manual and it reading as a 2 piece metal. Could be wrong. I'll check it again tomorrow night when I get home.
Thanks again guys, gotta scoot!
Dak

 

[LEB Ben]

No, Ive got the original 460.... stickers, matching numbers and all. Isn't that a 385 series?..

Dammit...I'm all over the place with your truck today...first thought it was a '79 when looking for parts, and then listed the 4x4 V8's...my apologies.

On my engine-- you're correct. It is usually made out of rubber or teflon. I'm assuming your engine is pretty similar.

Yeah pretty sure it is a 2 piece silicone seal, might have a metal core though...but that wouldn't really make sense.

 

[1985 Ford F-150]

Ok I thought it was an FE till I noticed the year. I really dont know on 335/385. I cant remember what it is exacly on an FE but theres two halves of a rubber circle and they go in and ya have to stagger em and not make em flush with the main cap and block. Then theres two straight chunks of rubber that ya insert into two slots on the sides of the rear main bearing cap then ya put a finish nail in there to hold the rubber in.

 

[cumminsnorth]

Make sure it is the rear seal I thought that my rear seal was leaking but it was the oil pressure sender!

 

[LEB Ben]

Make sure it is the rear seal I thought that my rear seal was leaking but it was the oil pressure sender!

Yeah...that's true too...come to think of it, a rear valve cover leak can look the same too.