Hi everyone, I have another question regarding the spacer bush...
I bought a new shaft seal and new slip ring, but in reassembling something seems to me wrong, the spacer bush I have not bought a new one, I used the old one because it looks like the same but I have the impression that it is too long for the new slip ring.... 
If I tighten the bolt the spring of the slip ring, is compressed so much that it blocks the shaft and does not make it turn, however, loosening everything is fine and I have the impression that the spacer Bush is 2mm too long.... I'm doing something wrong or I need to buy a new spacer bush?
thanks

Are you installing a stamped metal impeller or a cast metal impeller?

Laitch wrote:Are you installing a stamped metal impeller or a cast metal impeller?

I already had the stamped one as standard

Zisco wrote:. . . the spacer bush I have not bought a new one, I used the old one because it looks like the same but I have the impression that it is too long for the new slip ring..

When installing the new style seal, a different bushing must also be used as in this illustration. It is a shorter bushing

Thanks for confirming, the old one is 13mm while the new one seems to be 10mm from the picture, I can’t see clearly... could I miling the old one on the lathe and lower it by 3mm what do you say?

Zisco wrote: could I miling the old one on the lathe and lower it by 3mm what do you say?

I say if you have the skill, the equipment and the measurements, do it but replacing these seals is not a job you'll want to do, or buy parts for, twice although some of us have. 

Laitch wrote:

Zisco wrote: could I miling the old one on the lathe and lower it by 3mm what do you say?

I say if you have the skill, the equipment and the measurements, do it but replacing these seals is not a job you'll want to do, or buy parts for, twice although some of us have. 

I have a friend who works with the lathe by profession, so it is not a problem but I should know the precise measurement, if 10mm or 11mm because the image does not show well…

I have already replaced the seals and everything went well… only this spacer bush is missing to close everything

[size=32]11 51 1 464 902 bushing is an approximately 6 Euro/$10 bushing which fits many '70s-era BMW cars and Bricks.[/size]

Two Wheels Better wrote:[size=32]11 51 1 464 902 bushing is an approximately 6 Euro/$10 bushing which fits many '70s-era BMW cars and Bricks.[/size]

Yes but with ship 6+6= 12€
my friend would lathe it for me for free

Based on unknown dimensions, yes. 

I'm just about to rebuild a pump. It had the old type seal - at least I think it did - it was destroyed when I heated the bush in order to remove it from the impeller shaft on disassembly. The new seal should be with me tomorrow. Last time I did a 'new for old' rebuild was a good few years ago, but I do remember that Motorworks recommended that I replace the bushing and that's what I did.
This time I have a lathe to alter the old one, which is 13mm as mentioned. I'm working on the theory that there'll be a small about of axial leeway viz the length of the bush, courtesy of the spring within the seal. Therefore (theory again, sorry) I'll aim to place the lip of the new seal over a good bit of the impeller shaft - and I'll do this by shortening the bush to suit.

Pics to follow, dimensions of the shortened bush also. This may help, or it may be a load of codswallop 

Two Wheels Better wrote:Based on unknown dimensions, yes. 

that's why I'm looking for the dimensions otherwise I don't do it and buy the new original one…

chris846
Pics to follow, dimensions of the shortened bush also. This may help, or it may be a load of codswallop 

I look forward to the photos of the change you will make goes thank you very much

Have a squiz at this:
K100 Forum Water Pump Seal thread

Hang on hang on guys - my memory is duff and it's been a long time.

....been reading about this 'cos something doesn't seem quite right, so please, advise or confirm...

The short bush in the pics in theis thread, is 3mm shorter (ish) Is this the SAME 3mm that at one time guys were machining off the old type cast impeller so's it could be used with the new type SEAL?

...In which case a pump with the later pressed steel (thin) impeller....uses the longer bush.

Put another way:

Cast impeller + v early type seal (that everyone's forgotten about) + 13mm bush = okay (original design)
Cast impeller + later (longer?) seal = shorter 'conversion' bush required (this setup occurs with a repair)
Pressed impeller (3mm thinner than cast impeller) + later seal = the 'normal' i.e. 13mm bush

Help needed. I know this has been done to death, but I have been researching old threads as I should, and this is the conclusion I'm coming to 

Chris, that is what the old boys at the Beemer workshop used to do with the cast impeller situation twenty years ago, yes. 

New, longer bush, 'new' type seal, stamped impeller. I've spent my six Euros worth fussing already.

Cheers TWB
So the short bush in the service bulletin (post 104) was a 'special' to allow repair fitment of a new (longer) seal to the old cast impeller - for the guys who didn't have the wit to stick the impeller in a lathe?

...I must seem really thick.

Maybe I am 

Losing it...

The cast impeller doesn't have a spacer at all (haynes manual).

Machining 3mm off the cast impeller (TWB's post plus other, old posts) must've been done so's the 'new' seal could've been fitted.

The pressed impeller has a 13mm spacer bush (it's on my bench in front of me)

....so what's the short-looking bush in post 104 for? It's got the smaller diameter spigot on it, which fits the oversize hole in a pressed impeller, to centre it. Therefore, it seems to be for use with a pressed impeller?

And why does Zisco's pressed-impeller pump seem to need this shorter bush too?

Where's Scooby, Shaggy, Jeff, Daphne and the other one when you need them?

 "Twat!"

I try to explain this with my bad english…

I have a k100 16v and this it already mounts a pressed impeller and not a cast impeller… 
however the water side gasket has been changed, now there is the new model with the spring which is longer than the previous model, which is why the spacer bush is shorter than my long spacer bush (13mm), so theoretically shortening my spacer bush by 3mm everything should fit well…

Should've known....check with Anton 

http://largiader.com/articles/waterpump/

Now gone, but still saving the day, God bless.

Basically:

Cast impeller + old seal = okay (early OE setup)
Cast impeller + new type (longer) seal = shorten impeller by 3mm in lathe 
Pressed impeller + 13mm bush + old seal = okay (later OE setup)
Pressed impeller + shorter bush + new type (longer) seal = okay (final OE setup)

You can either buy the shorter bush, or shorten your own to around 9mm overall length (per Anton)

thanks chris this is very helpful

The below just confirms what Anton describes in the link:

 The original bush is 13mm (the pump that I'm fixing therefore had the pressed impeller, and the old, shorter seal)

 The counterbore in the 13mm bush measures 9mm 

 With the seals installed in the pump, and the shaft drawn through the water side seal until the gear (on the other end of the shaft) is flush with the rear face of the pump, the shaft projects 6mm through the seal.

 This requires 3mm to be machined off the rear face of the bush....

 ...to give a new counterbore depth of 6mm.

 Well it all seems okay!

if you remove 3mm you have a total of 10mm .... Anton was talking about shortening it to 9mm ....
in the afternoon i took the space Bush to my friend to do it 9mm.... he won't have done it yet, but I don't think 9 or 10mm makes much difference

I would say its the depth of the counterbore that's important. The 13mm bush has a 9mm counterbore, a bush shortened by 3mm has a 6mm counterbore. If you shorten the bush by more, the counterbore will be less than that. 

I think it would only be an issue if you hadn't drawn the shaft fully through the water side seal on assembly. If you hadn't then a 6mm depth bush would finish the job and draw the shaft through fully when you tightened the impeller bolt. A 5mm depth bush wouldn't do that.

The new type seal contains its own spring pressure, unlike the old seal which seems to rely on some axial compression from the bush. I think that's why Anton advises that the length of the shortened bush for the new type seal isn't critical.

However, I did measure things up today just to be sure.

By me, with the seals installed in the pump, and the shaft drawn through the water side seal until the gear (on the other end of the shaft) is flush with the rear face of the pump, the shaft projects is 6,90mm through the seal, just measured.... and I noticed that if I put pressure on the shaft so that the seal spring compresses a bit, the shaft turns even better, so in theory I would need to shorten the spacer bush by 2mm that is to say it becomes 11mm and not 10 or 9mm ... perhaps due to the fact that the first time I tightened the bolt with the 13mm spacer Bush to maximum, so the shaft is all pulled into the water side gasket .... I don't know what to do now, maybe it's better to tell my friend to shorten 2mm

I wouldn't worry, I think the only danger with the new type seal is rupturing it - stretching it - by trying to force the shaft through it. It doesn't sound as if you're in danger of doing that. I would shorten by 3mm and leave it at that. If it turns out that the seal is damaged from your earlier attempts, then at least you know that the bush will be correct for the replacement seal.

I pushed the shaft a bit out and now the shaft projects is 5mm through the seal, so as you say, by shortening 3mm I have a 6mm counterbore, which once the bolt is mounted and tightened, this pushes only 1mm on the spring watergasket.... 
tomorrow I call my friend and tell him to shorten 3mm 

That sounds encouraging 

Just for completeness, today I dismantled the leaking pump that I've just replaced. It's the first time I've taken one apart without the old seal disintegrating into a gazillion bits of unrecognizable crud. So I though I'd share what I found:

 With the impeller and 13mm bush removed, the exposed shaft measures around 8.5mm. 

 With the shaft removed, a sealing washer falls away (top left in the pic) This houses a small, removable rubber lip seal that is a close fit on the shaft. The seal therefore seems to be in two parts: the sealing washer, and the seal main body which is pressed into the pump housing. When in place, the washer rotates with the shaft and bears on the static upper face of the seal, which seems as though it might be some sort of ceramic.  A smooth wear pattern is evident on the underside of the washer (it is upside down in the pic) The upper face of the seal sits on a coil spring contained within the main body of the seal and is sprung upwards/forwards. The main body of the seal therefore seems to be like a small bellows that is compressed slightly by the sealing washer when the impeller and bush are in place and the bolt is tightened. For this type of seal I imagine that the depth of the counterbore in the bush (9mm) is important, because of the requirement for a small amount of axial compression on the seal to make it work.

UPDATE: the spacer bush is shortened by 3mm,I have assembled everything perfectly, now the shaft turns very well without forcing  
thanks for the support.

https://imgur.com/N08yNzz
https://imgur.com/HNVoZ6y

I'll post this here rather than creating a new post as it is water pump seal-related.

I just opened my K75's water pump cover and see what looks like a new impeller so I am guessing that the PO replaced it ( I have no idea of the history). I also see that Red sealant has been (clumsily?) used which has been discussed previously. My question is simply does this look to you guys like the sealant has failed and so needs to cleaned off and reapplied with a 1/8" bead? Note there appears to be a bit of oil mixed with the pooled coolant that you can see in the pictures.

Cheers
Ken

I don't know if the sealant didn't hold well, but my advice is take it out and fix it

The pump is out and I cleaned the overzealous amount of red sealant that was everywhere. I'll reinstall but won't be able to test it works as the bike is a project and a  few months away from running  

Hi

I can appreciate the situation....
Many years ago, I purchased four original water seals from Motobins.
I think it was approximately ten years ago and most likely NOS stock.
I still have the original shaft. Of course the threaded section of the shaft was damaged when I loosened the nut.
I took it to a machine shop and they replaced the threaded section with an almost identical component in less than fifteen minutes. I was charged $20 AUD.
I used a socket to hammer the oil seal and water seal into position and used Renzoil? Sealant. 
Five years later, still going strong.
My issue was trying to install the o ring. 
I’m not certain what I am going to do when I eventually replace the shaft.....