Flywheel Seal-Did I do something bad?

[Gunter]

Chris:
Thanks for the pictures and the threads.

How far does flywheel seal protrude?

From what I have seen on this, and other threads, half the people say it doesn't matter, and the other half says: flush (Or a little past flush)
The one reply with picture showing the seal all the way into the recess states that the engine run dry.

When a seal leaks, there could be many different reasons.
Seal not installed square to the crank,
Insufficiant contact of the lip due to rough surface, or worn area on the crank-shoulder, or differences in diameter.
Bore out of round.
Crank not centered in bore.
Seal installed without sealant on the O.D.
Damaged lip during install.

Unless I am missing some unknown factor, if everything is optimal, it should not matter if the seal sits deeper.
And why did Porsche engineer a deeper recess for the main seal but not for the seal in the #8 nose-bearing?
What actual pressure inside the case is applied to the main seal?
Certainly not the high pressure from the pump.

I guess I am looking for someone who installed the seal (With everything optimal) deep into the recess and either had no leak, or can give us actual reasons why this caused problems.

[plymouthcolt]

I just replaced my rear main seal in addition to my clutch.

Attached are pictures of the old seal prior to removal. If you examine the pics closely you will see it sits even with the case. I purposely tooks these pics for reference for anyone replacing the seals as this question comes up often. I hope this helps.

I installed my new one flush with the case.

[88-diamondblue]

I put it on while I was putting the case halves together. My concern is that it was too far into the case and the squeeze out from the sealant caused the leak. If I did it again I would put the seal in after mating the case. Will take pictures and let you know what happened. Will be working on it tonight.

[Gunter]

Howard:
Thanks for the pix; That's what I call a leak!
Looks like it is coming from the lip. I take it that the damage on the seal is from a screwdriver prying it out?
The notch shown on top is meant for "hooking" into the old seal for removal.
What is that red stuff towards the pilot bearing O.D.?
Did you install the new seal dry?

Michael:
Much appreciated. Must have been a lot of "squeeze-out".
Will you install the new seal without any sealant on the O.D.?
My feeling is that a VERY THIN layer of Curil-T will act as a lubricant to ease the new seal in and act as a sealant on the O.D. after.
After more research: It seems that most people install it flush although there are some who went a little deeper. The Porsche installation tool insures that it sits square but will allow to go past the case-edge.
To my mind, the most important issue is to insure that the seal sits square. If it is installed without the tool, the edge serves as a reference point to stay square.
The bore has to be true, the surface on the crank has to be smooth/polished for the lip to ride on.
There is a small hole in front of the seal (Under the #1 bearing) to allow the oil to circulate but, the hole is not on the bottom, it's more to the side.
Some other engines, like my Volvo, have a groove machined all around in the case so that any oil from a leaking main seal is caught and drained out without any harm.
Hope that the second install will work out and any pix are much appreciated.

[CBRacerX]

I got my 964 case back from the machine shop today. Take a look at these pics, there are two drain holes behind the seal, and if you push the seal all the way into the case you will absolutely block them. Then where will the oil go?

Yeah, exactly

[MBEngineering]

HI maybe you can see now why you do NOT put the seal all the way in, not only the hole blocked off, the inside of the lip on the seal is up against the case as well (have just pulld a 3.6 in bits and checked), so very little or no oil return, oil presure from the rear main will build up and you have a leak!!!.
did your mum not tell you to put things back where got it from?? IE; put the seal back as you found it, flush with the case, P9126 fits the seal just in from the edge of the case.

regards mike

[Gunter]

Thanks Chris:
The question was about going a little past flush, not to push the seal all the way in.
Your pictures doesn't show the bearing.
The #1 bearing is different from all the others and has a shoulder on each side making it impossible for the seal to block the holes even if the seal is all the way in.
I am not promoting to install the seal against the #1 bearing; I am saying that I cannot see a problem with going a little past flush.
After looking at different posts, some people have gone a little deeper without problems.
There can be a variety of reasons for a leaking main seal other than position. Most seals are installed flush and still leak because of other factors.
Please, install the #1 bearing halve and measure the distance from the case edge to the bearing shoulder; then measure the thickness of the seal and give us the numbers.

[plymouthcolt]

Originally posted by Gunter
Howard:
Thanks for the pix; That's what I call a leak!
Looks like it is coming from the lip. I take it that the damage on the seal is from a screwdriver prying it out?
The notch shown on top is meant for "hooking" into the old seal for removal.
What is that red stuff towards the pilot bearing O.D.?
Did you install the new seal dry?

Damage is from screwdriver. I have no idea what was that red stuff. I lightly coated the inner portion of the seal with fresh oil then tapped it into place with a block of wood.

[88-diamondblue]

These are the pictures after removing the leaking seal. I used yamabond 4/Threebond 1104 to seal the outer perimeter of the new seal. Was so impressed to see how it sealed the cam towers to the heads. Had to remove somehing to fix it and the sealant sread was perfect The first picture of how it looked after being installed the first time. The first time I used yamabond 5 to seal it.




After removing the leaking seal


New one installed and did not leak after a 25 mile run to start the breakin.

[Gunter]

Howard: Just oil on the lip but no sealant on the O.D.?
Thanks Michael: Good news: No leak. Great pictures, ignore my PM.
I wonder if the 3.2 case is different from the 3.0 because I don't see the overhanging shoulder from the #1 bearing in your second picture.
In Wayne's book, page 130/131, the end of the crank-area shows different: The side of the #1 bearing creates a groove/channel for the 2 oil holes, the crank has a portion on it to be in front of the #1 bearing when installed.
Is the 3.2 case different from the 3.0???

[Gunter]

The #1 bearing has thrust-flanges to control axial play of the crank.
The crank has flanges to fit precisely into the #1 bearing leaving a groove/channel for the 2 oil holes in the case.
When removing the main seal, the outer thrust-flange of the crank should be visible.
When removing the old seal, how deep is the recess in the case? xx mm?
How thick is the main seal? xx mm?
Is the case from a 3.0 different from a 3.2 in the main seal area?

Expert comments, and measurements, much appreciated.

Why is the thrust-flange from the crank not visible in this picture?

[Wayne 962]

Originally posted by Gunter
On page 135 of Wayne's book, the main seal is clearly past being flush with the case. So, how far is too far?

That's an optical illusion from that photo and the lighting - it's basically flush with the case - I use the end of a tool to tap it in, using the case as a stop-point. I'm not sure why that photo looks like it's not flush, but at that point, it is, or at most, it's about a 1/16th of an inch into the case.

-Wayne

[Wayne 962]

Here's a better photo:

http://www.pelicanparts.com/techarticles/911_clutch_replace/pic15.JPG

-Wayne

[Gunter]

Great shot of an old, leaking main seal.

Wayne: My question still is:

On the engine you rebuild for the book: Was there any leak from the seal shown about 1/16" past flush on page 135?

Much appreciated

[tobluforu]

Originally Posted by 88-diamondblue

These are the pictures after removing the leaking seal. I used yamabond 4/Threebond 1104 to seal the outer perimeter of the new seal. Was so impressed to see how it sealed the cam towers to the heads. Had to remove somehing to fix it and the sealant sread was perfect The first picture of how it looked after being installed the first time. The first time I used yamabond 5 to seal it.




After removing the leaking seal


New one installed and did not leak after a 25 mile run to start the breakin.

I'm about to install the RMS in my 72, just took the old one out which was 16 yrs old and it was light tan in color. I have the dark brown model and will be installing with curil t. I cleaned the heck out of the area and used fine steel wool to remove any burs. My question is the goop that is applied at 11 oclock in this pic, what is it and why was it done?

[brads911sc]

neither of these posts even mention pushing it in to far. why post unrelated threads?

Originally Posted by CBRacerX

Rear Main Seal Hell - Pelican Parts Technical BBS

Crankshaft Flywheel seal - Pelican Parts Technical BBS

[john walker's workshop]

the drain hole is well up away from the outside of the bore and the outer edge of the seal is thin enough that if pushed in all the way will not block the hole in the least. side view shows the seal lip is inset from the seal outer edge, so it will not rub on anything as well. this was from a 964. same as 3.0 and 3.2. it should be installed flush with the case, but if the crank has a wear mark from the seal, then you shove the seal in a bit.

[lindy 911]

Tobluforu,

The "goop" you see at 11 O'clock is epoxy sealing up the oil galleries. It is necessary. I would NOT use Curil-T on the MRS as it will come out. I put them in dry as long as the bore is in good shape for the perimeter of the seal. If you need to use a sealant, Yama-bond is a better choice.

Lindy

[tobluforu]

Originally Posted by lindy 911

Tobluforu,

The "goop" you see at 11 O'clock is epoxy sealing up the oil galleries. It is necessary. I would NOT use Curil-T on the MRS as it will come out. I put them in dry as long as the bore is in good shape for the perimeter of the seal. If you need to use a sealant, Yama-bond is a better choice.

Lindy

Thanks and its strange that so many either use curil t or a form there of, or install it dry. Even wayne says to use it (curil T), but JW states to install dry as well as you. The bore seems pretty clean and I don't feel a ridge, but the seal was leaking. I know Curil stays in some what of a wet state, does yama bond actually dry? What kind of epoxy is that?

[lindy 911]

Yama-bond drys but stays somewhat pliable. Many use JB Weld epoxy and there are some other brands recommended. The reason your old seal leaked is because it was 16 years old. The factory puts them in dry and I doubt that your seal was leaking from the perimeter, so sealant won't help anyway.

Lindy