BMW K100/K75 Waterpump woes [SOLVED]

[sebas2357]

Hello Everyone,

I'm in the process of rebuilding the water/oil pump on my 1985 K100. I've run into some issues that I need some insight on. The water pump on the bike is the old style cast iron impeller with a nut instead of a bolt. I understand that the new seals don't work with the cast iron impeller, and replacement of the impeller is required. I believe I have all the parts required to rebuild the pump. The issues that I am currently stuck on are these:

1) The water pump seal (11 41 1 460 329)  doesn't seat or slot into the pump housing, even with taps of a socket and mallet. The pump seal just sits where the old style seal would go. Is it meant to slot in the same spot of the old style seal, or is it normal for it just just sit in the housing?

2) Ignoring the pump seal concern, if I fit the slip-ring seal (11 41 1 741 870), the impeller shaft becomes too tight when re-applying the nut to the torque spec. This prevents the impeller from freely spinning.

I believe the solution would be to purchase the new style shaft/gear (11 41 1 461 793), which I think would solve issue #2, but I' not sure about issue #1. Would I be better off simply purchasing a completely new oil/water pump? I've observed that others have had difficulties rebuilding the old style water pumps.
I have attached some photos to aide in my explanation.

Seb

[Laitch]

Have you been trying to install seals in that filthy bore or is that a before-cleanup-and-installation photo? Did you purchase the new spacer bushing? The pump shaft looks worn and damaged from this distance. Post a closeup of it. A new shaft and bolt would likely be preferable.

Only careful adherence to procedure, and installation into well-cleaned surfaces will enhance your chances for success.

[sebas2357]

I took another look at my pump bores, and after some scrounging of other forums, realized that the "filth" you referenced was actually another seal I didn't remove.....  It had a metal feeling to it, so I thought it was part of the pump itself. I'm going to order a new shaft since I've seen that the old nut style one sometimes fails and causes some catastrophic damage. I believe the shaft is too pitted to re-use anyways, so that solves that.  I've added more images to reference.

Thanks for the help,

Seb

[Laitch]

Surprise!

Do you have a clear set of instructions to follow, Seb? There are some well-illustrated ones to be found.

[sebas2357]

Yes, I've been following the guides over at IBMWR and a video guide by kennyraceboy on YT which wasn't posted too long ago. These guides and along with the extensive information on the forum has helped tremendously.

[Laitch]

 

[alabrew]

You DID order 2 sets of seals, didn't you?
Notorious for failure on the first attempt.
If you have 2 sets, magic occurs and you will get the first one right.
Only one set, well...

[sebas2357]

I'm aware of the seal fragility and hindsight tells me I should've ordered another seal given that I ordered the shaft, but I'm hoping I'll get lucky and not damage the water seal upon installation. Worst case scenario, I'll order another seal and let the dealer fit the seals for me instead.

[alabrew]

That is what I ended up doing long so many years ago.
Unfortunately, the only dealer was over an hour away, but they got it right.

[sebas2357]

Well, I took it to the dealer to have the seals fitted... and they said they're weren't willing to fit them given that the bike is too old for their comfort. The next closest dealers are 1hr and 30m south or 2 hours north. I'm gonna attempt it myself, hopefully I get it right.

[Laitch]

Well, I took it to the dealer to have the seals fitted... and they said they're weren't willing to fit them given that the bike is too old for their comfort.
I'm gonna attempt it myself, hopefully I get it right

What you have there is a dealer that isn't desperate.    Follow the instructions you have, keep surfaces clean. If parts won't fit with moderate pressure, determine the reason before proceeding. You'll need sealant for the mating surface of the pump to the block. Get some Three Bond (DreiBond) from the dealer. It's BMW's go-to sealant; I use Permatex Ultra Black. Apply a bead around the pump's mating surface as depicted in your reference sources, then bolt it up.

I'm not an ardent supporter of hope in motorcycle maintenance. Patience, understanding, focus and determination have been more useful to me. My hope supply is already fully deployed in winning the lottery.
Check in here if you get stalled.

[sebas2357]

Good news and bad news..

Good news is that I managed to complete the job and install the seals without compromising them. Bad news is that I may have just completely screwed myself. I had installed the front cover and remembered that I had to torque the pump bolts, no biggie. I removed the cover and began torqueing the bolts. Everything was going well until I torqued the second interior pump bolt. I set my wrench to 5lb-ft of torque and felt that the wrench would never stop spinning. One more turn... click... the damn bolt snapped. I'm pretty sure the snapped bolt is going to be an issue holding fluids but I' m going to try tomorrow anyways after the gasket sealer cures and see what happens. Any advice for this? I've attached the picture of the bolt.

Edit: After some cool-headed thinking, I believe I could remove the water pump again, which should expose the remaining portion of the broken bolt. I'd rather not fill it with fluids, only to have to drain it again in case it leaks from the missing bolt. I'm going to try to locate a replacement bolt and attempt the above. 

Seb

[Laitch]

I think your torque wrench setting was too high and you misread the scale. What is the scale range of the wrench you used?

Did that bolt resist extraction and you needed to apply more force to it than you expected?

[sebas2357]

The other bolts all torqued just fine, which stumps me as to why it snapped. My wrench goes in increments of single foot-pounds up to 50. When I initially removed the bolt, it was tighter than the other interior bolt, which could partially explain why I snapped the bolt. I'm going to order a replacement bolt, remove the water pump, extract the broken bolt, and re-install everything.

[Laitch]

Does the broken stub extend above the hole in the block?

[sebas2357]

I'm not quite sure yet. I'm going to remove the pump now and report back if the stub does indeed extend out of the block.

[sebas2357]

Fortunately, the stud does extend out of the block. It's pretty tight at the moment, I tried utilizing pliers with runner ends to no avail. I went out and bought a stud extractor but unfortunately these only remove 6mm studs at the smallest setting. It seems that the bolt stretch itself below 6mm, so the stud extractor couldn't make contact with the stud. Any suggestions on the best method to remove it? I've added an image of the stud.

Seb

[Laitch]

Any suggestions on the best method to remove it? I've added an image of the stud.

Heat it with a hair dryer, heat gun or propane/Mapp torch, then soak it with Liquid Wrench. There will be some smoke; that's ok. Tap on the top several times with a hammer then go have a cup of coffee or work on your stamp collection. In ten minutes, come back, put a vice-grip it and wind that sucker out of there. If it doesn't move, heat-soak-tap-wait again. Sometimes, trying to rotate it back and forth a little helps break corrosion. That sequence is how I remove all seized fasteners using patience.

[CTDOM!]

If you don't have a set of needle nose Vice Grip, you need to go buy some.  There is enough there to grab with those.  With Laitch's heat and those vice grips it should make short work of it.  Clamp it tight perpendicularly not straight on.

If I understand correctly, you just put this screw in so there shouldn't be any real corrosion so it is just the torque most likely holding it in.  Go slow.  Use the extractor as the last resort, every time I have the bit walked and damaged the hole.. I hope I caught you in time!

[sebas2357]

Laitch and CTDOM!, you guys are absolute life-savers! Thank you! With your guys' advice, the stud came out with only one soaking . Now, time to reassemble everything correctly.

[Laitch]

What is that ring around the threaded shaft? Check the hole for threads broken by cross-threading if you cannot identify that ring.

[sebas2357]

Nothing serious, just old gasket that made it's way into the thread.

[CTDOM!]

NICE! 

[sebas2357]

Unfortunate news fellas ... After waiting for some terminal nuts to arrive from NGK, I finally got around to filling the oil and coolant and discovered that the weep hole is now slowly dripping coolant. I'm assuming this is probably going to require a dissembly of the water pump along with another set of seals replacement. Is there any break-in for these seals? Or is the immediate drip a sign that the seals were damaged upon installation?

[Laitch]

A successful pump restoration will not be followed by leaks of either oil or coolant, seb. If it is a slow leak, you can still ride the moto; be mindful of the coolant level in the reservoir and top it up to the MAX line before it reaches the MIN line.