Mak

The rear main seal on my 425 is leaking (67 Delta 88). Not terrible yet, but definitely leaking. I usually only drive my car on weekends... I park over a drip pan and each week have a about a half dollar size spot. From what I understand it's a rope seal, yes?. Basically I'm starting to plan whether to take on the job myself or find a shop that I think can handle it. R&R'ing the trans is no problem for me... but I have no experience with a rope seal. So what's involved? Does the engine have to come out... or can it just be jacked up in the engine bay? How is a rope seal replaced? Is there a neoprene replacement seal available? Any other pitfalls to consider? Any advise will be appreciated.

Lady72nRob71

PITA...
At least from what I have seen amongst various engines...

Have you concluded it is dripping from there and not from a valve cover, pan or intake?
I am guessing you have but it is easy to forget how oil always seems to run down and drip from that spot.
I have a very slow drip from mine and traced it to there. When the engine needs to be rebuilt, it will get resealed.

MDchanic

Yes, you can jack up the engine, pull the oil pan, pull the rear main bearing, and work the seal out and a new one in, then put it all back together (procedure is in the Chassis Service Manual), but is is really worth it for a 1" spot of oil a week?

On the other hand, you could pull the engine to do it, but then you might as well...

If it were me, I'd park over a drip pan and forget about it.

- Eric

Mak

Yeah, I'm sure (unfortunately). I've already replaced the valve cover gaskets (that were leaking)... steam cleaned the engine and did a dye test... definitely the rear main.

Mak

I hear ya... a minor oil drip on a 45 year old car is not unacceptable to me. What I didn't mention is my transmission also leaks from the front seal... it's actually worse than the oil leak. Pulling the trans & resealing the pump is no problem and I'm definitely going to do that... just seems like a waste to re-install the trans without addressing the oil leak, but I may do just that. The actual installation of the rope seal is what scares me... I've heard of people that aren't experienced with them having the new seal leak worse than the old one! I guess there's no neoprene replacement seal that can used instead?

My engine & trans both have less than 10k miles since they were rebuilt... so wouldn't anticipate having to do much more. I think where I went wrong was letting the car sit for over a year and a half without starting it... I figure during that down time the seals dried out & shrunk. Other than the leaks, the engine runs great & the trans shifts great!

Lady72nRob71

Looks like I might have another anti-MAW helmet sale in the works here!

Yes, I think I would let it be for now.

Oldsmaniac

There is a neoprene seal available sold under the Ford BB seal. I would not install a new rope seal as you are not pressing it in place in the top only rolling it in and results will be iffy. Make sure it is not the oil pan rear seal leaking which is more common than the rear main.

Mak

Thanks for the tip! I'm 90% sure, but not positive... as it only leaks after driving it and then parking for a while... sure looks like there's oil above the lip of the pan, though. I guess my next step will be to get it up on the ramps & clean it (again)... and just lay under it while it's running for as long as takes to make sure. If I confirm that it's the rear main, I'll be interested in more info on the Ford seal. Thanks again!

MDchanic

Since you're going to pull the trans, you could always shore up the engine and start it with the trans off of it, then watch carefully for leaks from the back. They'll be easy to see with the trans off.

I don't have the part number for the Ford rear main seal at my fingertips (I think the big block seal was from a 460, and the small block seal was from a 292), but I know it's around here somewhere, and I can find it if nobody else can.

- Eric

bigD

yeah it's the 460 seal... you should be able to go to any parts store and get it.

just ask for a neoprene rear seal for a 460...

Oldsmaniac

and make sure its facing the correct way when installed.

75cutty455

I know this is an older thread but I have to ask because I am getting ready to pull mine out and replacewhat I think is the rear main seal I have a slight oil pour coming from mine. When I pull in the garage I can follow the oil drips all the way up the block.


Oldsmaniac,

What is the difference in the rear main seal and the oil pan rear seal. I thought they were the same seal.

Oldsmaniac

They are not the same. The seal for the oil pan rear is just that and rubber. The rear main seal is around the crank and under #5 main bearing cap and is either rope or hard neoprene and is 2 pieces. A manual will picture both.

MDchanic

- Eric

75cutty455

WOW. I don't remember if I put one of those under that bearing cap or not. I guess I'll find out when I take it apart.
I read on another thread that I should put it at a bit of an offset angle so that the seal is not in the same spot as the mating surface of the main and the block, and add a dab of silicon where they meet. Is this accurate?

Thanks a bunch.

Anwar

DeltaPace77

I realize this is an older post too, but a common one. I have an engine picker and stand, and always find pulling the engine the best way. If not sure where the oil leak is coming from, put some UV trace dye in the engine crankcase, and scan with with a UV light later. I have a Ford 460 BB neoprene main seal on my 455, but really need to pull the crank, and have the rear main rope seal oiling slashes machined off, or gonna be trouble.

75cutty455

Took the oil filter and #5 cap off last night. Lo and behold there wasno seal there at all. I was thinking what a *****. Anywhoo.... Its in there now.

However, BEFORE i seal it up again I have one question about the positioning.

The Correct way would be with the widest flat side facing the front of the engine?

Another way of saying this would be if the seal were a sideways "V" ( > ). The side with the wide end would be facing the front (water pump end) and the smaller side of the sideways "V" ( > ) would be facing the back (fly wheel end).

Forgive my elementary description. I just want to be 100% sure before I seal it up again.

Thanks a bunch

Oldsmaniac

I assume you also put the top seal up and around crank? Some seals picture right direction and the Chiltons as well for a Ford seal. I always check as my memory is not that good...

oddball

It's a rubber lip seal, right? You want the opening of the lip facing the inside of the engine. Think of oil splashing towards the seal - you want it trapped inside the lip, and not have an easy path by just pushing past the lip.

Or, the wide end towards the water pump.

75cutty455

Yes I put the top seal on too.

Thanks guys. Thats how i did it. Just wanted to maKE SURE I understood the directions that came with it