Water Pump Shaft and Seal

[lewisnort]

Hi all,

I disassembled my water pump last night in order to rebuild it and ended up with a few questions.
This is the state of the shaft, the only mark I could catch with a fingernail is the very bottom line, though not dramatically so. I would assume this is reusable given the state of some others I've seen on this board and others?

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When I removed the new style stamped impeller that was already in there the spacer bush had another part attached to it with a rubber seal that I wasn't expecting to find from all the guides I'd looked up. I initially thought it was part of the bush but it did separate on the bench, is this lower 'ring' with a rubber seal part of the spring loaded seal that has separated? the overall state of that seal was awful and had completely broken down into its parts.

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Speaking of the horrific seals, the oil side of it has left quite a lot of nasty rubber residue in the pump housing, anyone know of an easy way of getting this out without scratching at it so I don't ruin the sealing ability?

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I did heat up the impeller bolt to get it off which might have melted the seals a bit, whoops! But there was no chance I was getting it off without given the force it took to break loose.

[Kaos]

I disassembled my water pump last night in order to rebuild it and ended up with a few questions.
This is the state of the shaft, the only mark I could catch with a fingernail is the very bottom line, though not dramatically so. I would assume this is reusable given the state of some others I've seen on this board and others?

That single seal sitting around that wear is the gandalf to your coolant.
Now the wear could be minor enough to still be sealed. But. Under pressure coolant doesnt need a lot to penetrate trough small gashes.
So risky, but probably yes.
What happens if it doesnt: contamination of your engine oil, itl turn Milky white like a salad dressing and wont provide the lubrication needed.
Dont let your coolant be a balrog

[lewisnort]

Dont let your coolant be a balrog

So really you're saying while I'm in there...
Sigghhh, I bought this bike for 600 quid, I might as well have bought a new K1600 when I'm done with it.
kpartsholland have a kit with the pump shaft included, between them and motorworks I'm not sure who would be better value for money considering I'm in the UK.

[Kaos]

Its quite worth it to Check the boneyards.
Maybe also wait for a second opinion from another forum member. (For me it came from personal experience and because of that preventing it while at it, is better than having to redo it later on -so basically trauma-)

[lewisnort]

I left this for a while and returned to it, attempted to give it a clean. I thought I had removed all the seals

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But it looked suspicious so I took at right angle pick and felt what I thought was soft under this metal shelf, does this shelf need popping out from the other side, or do I install the oil seal onto this surface? Begging for anyone with knowledge of this let me know before I end up destroying this pump.

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[Kaos]

There should be a shaft seal in the back which is a rubber ring. However it hard to determine if thats what i am looking at. But this is a concern:
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This is the exploded view of a pump:

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But because of the gash in the metal of the first image,
Seeing the spacer and slipring seal in your other images my best guess is, its ruined.

[lewisnort]

There should be a shaft seal in the back which is a rubber ring. However it hard to determine if thats what i am looking at.

Which item in the diagram is this seal? I understand this is for the old design but I presume the number of seals is the same.

As for the gouge I think it may be a trick of the shadows making it worse. Here's a better top down view, its not as a result of my poking and the 'shelf' is still flat if pitted.

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The rubber material I'm talking about is directly below this shelf but above the tapered section underneath it.
I watched a bunch of YouTube videos extremely slowly but no one mentions this as a seal, nor a parts diagram (that I can tell) but it certainly feels like an o-ring of some kind.
example of video I'm referring to. I'm at least relieved to see the 'shelf' I keep referring to in this video which leads me to believe I did remove all the seals, it just makes me more confused as to this mystery one.

[lewisnort]

I've attempted to recreate what I'm talking about in paint, so forgive the crude representation.

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[Kaos]

Well, at the very least its a relief that the pump doesnt have a gash.
But what you drew (almost art) is the oil seal and indeed is replaceable -to be picked out from the inside-, and i do see its not part of the diagram i shared.
However this is the part number: 11 41 1 460 328
This video shows the ring:

[Laitch]

Well, at the very least its a relief that the pump doesnt have a gash.
But what you drew (almost art) is the oil seal and indeed is replaceable -to be picked out from the inside-, and i do see its not part of the diagram i shared.

The oil seal is part #8.

[Kaos]

The oil seal is part #8.

Correct. However it appears that isnt or wasnt the ring hes after.
There is another "o' ring deeper inside the pump., as in the video, and that ring isnt shown in the diagram

[Laitch]

Correct. However it appears that isnt or wasnt the ring hes after.
There is another "o' ring deeper inside the pump., as in the video, and that ring isnt shown in the diagram . . . However this is the part number: 11 41 1 460 328

The o-ring with that part number seems to be in the diagram and is shown in the video, too. It is not "deeper inside the pump;" it is seated on the pump driveshaft section inserted into the engine case to connect with the output shaft. My guess is that all the goo being encountered within the shaft bore is from an oil seal rotted from neglect and perhaps even installed incorrectly. Attached is a photo of the pump driveshaft where the o-ring of Kaos's description is seated. Also attached is an updated diagram from the BMW K1100 workshop manual showing the o-ring in question on the shaft of the small drive gear.

[lewisnort]

There is another "o' ring deeper inside the pump., as in the video, and that ring isn't shown in the diagram

I have seen that video and it did give me a glimmer of hope I wasn't insane, but after watching it back over and over he is definitely just removing the oil seal, part 8, since you can't see the sealing surface prior to him doing so, what I referred to as the 'shelf'.
The oil seal sits on that surface, what I'm picking at is under it.
And as Laitch has said that part number is number 10 in the diagram.

I'm actually now proposing that the oil seal was fitted backwards? if you look at my stack of seals I removed that is exactly the direction they were removed in relation to each other. Perhaps some of the oil seal material has made it's way to here it shouldn't have?
It does have a conical shape at one side.

Bare in mind I have zero hours running this bike, it came to me as a non runner and I ran it for maybe 5 mins total before stripping it, so I won't have any knowledge of running oil leaks. Though the underside was covered in oil/mud.

The thing is as far as I can tell having a seal where I have indicated wouldn't have any practical purpose at all, there are no channels it's blocking, and there are no shafts that fill that void given the relatively thin feel of this mystery 'O-ring'.

[lewisnort]

For future reassembly reference it appears then that this section of the oil seal should rest inside the water seal as so expertly depicted below?

Screenshot 2025-09-07 230852.png (18.4 kB . 623x576 - viewed 92 times)

If that is the case then yes I think the oil seal was installed backwards, but clearly it worked to some extent because it's been there for some time.

[Kaos]

It is not "deeper inside the pump;" it is seated on the pump driveshaft

Thanks for the clarification. I was wrong and should not have let myself get absorbed in the hocus pocus.

For future reassembly reference it appears then that this section of the oil seal should rest inside the water seal as so expertly depicted below?

Screenshot 2025-09-07 230852.png (18.4 kB . 623x576 - viewed 92 times)

If that is the case then yes I think the oil seal was installed backwards, but clearly it worked to some extent because it's been there for some time.

The conical side of the seal should face the water seal

its probably also hard to determine if it was installed incorrectly when molten and purging it from the pump.
And its what we call "mustard after the meal" (freely translated). It doesnt really matter anymore what was, as long as re-installing is done correctly.