K75s -Rear Seal

[Ian T]

Hi everyone

Nob alert Nob alert

I’ve just replaced the rear seal in my engine and like a total nob (see above) I have put it in flush and not with the little .5 mm stick out bit that is prescribed.

Don’t know how it happened but it has.

I can’t see any reason why this should be an issue but allegedly it is.

In your experiences what do you think, don’t really want to take it out and buy another one but will if that is the recommendations.

Couple of pics.

Cheers

Ian


IMG_4157.jpeg (69.18 kB . 768x576 - viewed 107 times)
IMG_4158.jpeg (39.84 kB . 768x576 - viewed 110 times)

[Laitch]

Nob alert Nob alert I can’t see any reason why this should be an issue but allegedly it is.

Allegedly? To quote Inspector Callahan of the San Francisco Police Department, " Ask yourself one question, 'Do I feel lucky?' Well, do you?"


Did you change the output shaft o-ring, too? Anyway, if the seal going to allegedly leak as is, perhaps it will wait until you're psychologically ready instead of right away. The bonus of its leaking is it will sharpen your disassembly technique. That's a win-win.

 

[natalena]

There once was a Noob named Ian.
His assembly skills worth seein'
O-rings be damned, and seal be rammed,
Last ride had his rear seal a-peein' ... oil

Easier to correct now. What's a few quid?
Cheers

[daveson]

I'm running off a shakey memory here. I think some of the newer seals bottom out earlier. If it's the same as the original it's possibly ok.

I remember a quote about Bill Shakey from a graffitied dunny wall:

One would think,
With all this witt,
That Shakespeare himself,
Came here to shit.

[Laitch]

The service bulletin can be read and then interpreted to conform to individual belief and circumstance. Everybody's a winner. 

[daveson]

Was my memory good, or shitty?

Edit: lower instead of proud? Then it's more than just my memory that's shitty? I've been confused about that since when I first read it, that's one thing I do remember.

[The Mighty Gryphon]

Is there a groove worn into the clutch basket where the seal's lip presses against it?  If not, you are probably okay since the reason for having the seal sit proud is to have the seal working on an unworn surface for a better seal against leakage.

[Laitch]

I never ruminated about why the new pattern Teflon seals needed to be set at less depth than the spring-loaded seals, I just went ahead and did it because I am a slave to Authority, but after reading the typical BMWglish instructions umpteenth times, I've come to the following sleep-deprived conclusion. If the arbor for setting the old-style, spring-loaded seals were used on the Teflon seals, it could drive the seal's outside edge over the chamfer as indicated by the arrow. Whether that could happen was dependent upon the variation of depth in the block where chamfer were machined—a location that could be the "variation" in tolerances mentioned in the bulletin. The chamfer could deform a deeply-driven seal enough to allow oil migration between the seal and the block wall. Heat and oil pressure would eventually push oil completely past the seal, past the intermediate housing, and onto the clutch housing.

So BMW lessened the depth that the new-style seal was driven to account for variations in machining. The result is a new arbor was created to set the seal's outer surface at its current specified distance from the block surface.






IanT has a chance that his seal won't leak if it isn't low enough in the seal seat to deform on the chamfer. It's a calculated risk with reasonable odds and, like I mentioned previously, can make life interesting in anticipation of the outcome. If Ian takes those odds, a positive outcome would be useful information to provide the forum members.

Ian should also realize that he is not the first of us to screw up seal installation and that it is a comfort for many of us to know somebody else did it, too, so let's all thank Ian. 

 Thank you, Ian.

[sooprvylyn]

Cant answer whether there is any real issue with seating it flush, but, if you want to redo it, and want a tool for it....I posted a 3d print file of the tool in the Project Motobrick 3d Printing Emporium found on the home page.  I used it to install my rear main seal and it worked perfectly.

[Ian T]

Cant answer whether there is any real issue with seating it flush, but, if you want to redo it, and want a tool for it....I posted a 3d print file of the tool in the Project Motobrick 3d Printing Emporium found on the home page.  I used it to install my rear main seal and it worked perfectly.

Thanks and very much appreciated. Being the last Luddite I have sent the link to a child (daughter) who will have a look see and try and print one for me.
Great link thank you.
Cheers
Ian

[Ian T]

Hi everyone and thanks so much for all your helpful comments. There are some for and some against.

There are a couple of things for me, firstly although I’ve just fitted it I think I brought it about four years ago and I can’t remember where from. All the reading I’ve done suggests that the new seal is brown in colour and mine obviously is not and it appears to have a hard casing on it as can been seen in the phots. So I presume it is an older seal palmed off onto me as new. Also if I am getting this right the older seal was fitted flush. So perhaps I am ok as mine is flush.

But you know I really think I will buy another and replace it. Just gotta get me one of those tools and be gentle this time. Thanks again for all you very kind help, guidance and suggestions. Very much appreciated.

And some wicked poems

Cheers.

Ian.

[The Mighty Gryphon]

You don't need a special tool.  Just cut a hole that will fit over the seal in a piece of cardboard from a cereal box.  That is about the right thickness.

Start the seal into the engine, and slip the cardboard over it.  Tap the seal the rest of the way in with a piece of wood until the wood contacts the cardboard.  The seal will now be proud by the proper amount.  Done!  It's not rocket surgery even if it is a BMW.

[Laitch]

This is a new-pattern seal. Note the spiral rings. Ian T has a new pattern Teflon seal. Colors vary.

The words Trocken Montieren printed on the seal in his photo mean Mount dry. The old pattern seals having the spring garter within them were oil-soaked before mounting. The new-pattern seals are mounted dry. Some installers will use the barest skim coat of oil on the Teflon seal but it should mount perfectly into clean undamaged surfaces when it's dry. The reason the Teflon seal is mounted proud from the engine case is that its sealing perimeter is wider than the old style. If it is driven into the case too far the perimeter will deform on the chamfered edge and could leak. Inge explained this to us several years ago.

This type of seal needs the part that seals the shaft to be expanded before mounting so it does not deform. When it contracts after being mounted, it then seals the shaft surface.

If Ian just picked up the seal and drove it into position, it's liable to leak from both the interior and exterior sealing surfaces. There's always a chance that it won't, but it's clearly mounted incorrectly.

[sooprvylyn]

Just gotta get me one of those tools and be gentle this time.

If you have a pal with a 3d printer, you can print the one thats in the 3d print channel.  Someone else suggested cutting a hole in a cereal box...that might work too, but havent tried it.

[daveson]

Doh, finally I understand the drawing and the service bulletin, been looking at it wrong all this time. Hopefully you ignored my posts.

The pre-forming that Inge has suggested in the past, I think refers to the front main seal, where the lip of the seal makes contact with its sealing surface when the seal is installed. On the rear main seal it's lip makes contact with its sealing surface when the clutch basket is mounted (which is in the opposite direction compared with the front main seal) so pre-forming isn't necessary.

[Laitch]

The pre-forming that Inge has suggested in the past, I think refers to the front main seal, where the lip of the seal makes contact with its sealing surface when the seal is installed.

That isn't what I read in this thread. Read it and tell me if it changes your mind, daveson. 

[daveson]

Yep, I've changed my mind. I don't think I've seen one of those new seals.

Thanks Laitch, that was an interesting read, the on topic part of it especially.

[Laitch]

I didn't go further than Inge's instructions the first time I read it years ago. The only additional useful instruction in the thread was Rick G's recommendation for the debating society to get high and chill out.