Leaky rear main seal

[malibubronco]

I had my 73 bronco in the shop to have the 302 V8 rebuilt. They’ve done a lot of work for me in the past on a 67 Mustang I owned and a 66 Mustang that I owned and always been really good. I had the 302 rebuilt and it runs great but the rear main seal leaked not a lot, but it leaked after they rebuilt it so they tried it again put a new gasket in there and once again, so it’s like the third time now that they’ve done it and it still has a slight leak. Any suggestions I mean these guys should know their stuff and they’ve been doing it for a long time they’ve done quite a few. I’m stumped and so are they. thanks for your help.

 

[ba123]

And you're 100% sure it's the rear main?

Maybe it's the pan and just seems like the rear main, or trickling down from the valvecovers or PCV or somewhere up there.

And if it is the rear main, I'd recommend a change in which seal is being used cause after that many, ya might as well hit yourself in the head with a hammer.

Or, maybe they say they are doing it but aren't and hoping you get tired of it and leave them alone?

 

[maxellfullmoon]

I would get someone else to do it next time. Those are a 2 part seal and there is a certain way to install them. The lip faces the front and you don't want the ends of the seal to line up with the block and cap. You want the upper seal half sticking down below the block line about 3/8" and the lower seal recessed into the block 3/8" . And like ba123 suggested use another brand. Shouldn't go wrong with a Fel Pro.

 

[SLOWnEASY]

Are they pulling the motor or are you? If they are pulling I would insist on inspecting it when it's out. Maybe it's the brand of the seal and a different brand might seal a little tighter.

 

[malibubronco]

And you're 100% sure it's the rear main?

Maybe it's the pan and just seems like the rear main, or trickling down from the valvecovers or PCV or somewhere up there.

And if it is the rear main, I'd recommend a change in which seal is being used cause after that many, ya might as well hit yourself in the head with a hammer.

Or, maybe they say they are doing it but aren't and hoping you get tired of it and leave them alone?

Yeah, unfortunately, I’m sure the second time they had it up on the rack and confirmed it themselves. The engine builder who did the work so a third time and it leaks a lot less but it’s still a very slow leak, but it does leak down the less so they were talking about putting some kind of a dual lip Gasket. I don’t know all that much. I’m not an engine builder, but they’ve done a lot of work for me in the past they work on a lot of old classic cars mostly mustangs not a lot of Broncos.

 

[malibubronco]

Are they pulling the motor or are you? If they are pulling I would insist on inspecting it when it's out. Maybe it's the brand of the seal and a different brand might seal a little tighter.

Well, they made two attempts they’re gonna go for a third . The engine builder had just rebuilt the whole engine and they reinstalled it in the bronco and it leaked so then they installed a second one and that leaked and now they’re trying to figure out what to do.

 

[malibubronco]

I would get someone else to do it next time. Those are a 2 part seal and there is a certain way to install them. The lip faces the front and you don't want the ends of the seal to line up with the block and cap. You want the upper seal half sticking down below the block line about 3/8" and the lower seal recessed into the block 3/8" . And like ba123 suggested use another brand. Shouldn't go wrong with a Fel

 

[malibubronco]

They use the Fel pro two piece gasket and they offset it so that it wasn’t a seam on top of a scene when they put it in. I purchased the part for them. They let me purchase my own parts so I made sure I checked with a lot of Bronco guys to see what was best but it didn’t work.

 

[nvrstuk]

They use the Fel pro two piece gasket and they offset it so that it wasn’t a seam on top of a scene when they put it in. I purchased the part for them. They let me purchase my own parts so I made sure I checked with a lot of Bronco guys to see what was best but it didn’t work.

Then unless there was some machining or fit issue they installed it incorrectly. Needs a dab of sealer around the rear main cap, around the pan edge. Not too much but I can't believe it's the seal itself.
Edit: I forgot to mention that... that just sucks. Sorry it's leaking! Is it bad?

 

[Busamnoh]

I might be late to respond but I changed my seal 4 times in a row. Attempts were with RTV, with sealer and RTV, and without less RTV. I clocked the seals 3/8” every time and it still leaked. The last attempt was a success and with zero leaks 300 miles later so far. I did the below:

I Used Felpro 2901 instead of the standard Felpro BS30136. Its has the same dimensions, a slightly harder rubber and is made for performance builds.

No RTV around the seal or the groove, no RTV on the main caps. Just no RTV at all.

I cleaned the upper groove with a thin long brush, lots of break cleaner spray, and compressed air.

Used a thin line of permatex 51031 on the main cap and torqued to spec.

Using the Felpro OS13260 one piece oil pan gasket with a dab of RTV on the corners and by the chain cover makes the instal a billion times easier.