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Discussion Starter #1
I noticed that my coolant level had dropped a bit over the past two weeks with minimal riding due to the persistent winter weather. Checking the weep hole after removing the bottom fairing and running the engine shows coolant. So I guess it's time for a rebuild to be ready for another summer trip on the K75.

Finding the procedures by John Diaz and Don Forsman on IBMWR with great pictures it looks pretty straight-forward. I should be able to make a PVC seal driver like in the diagram.

So far my shopping list for Max BMW includes:
- shaft seal
- slip-ring seal
- pump to block O-ring
- oil gear O-ring
- impeller
- impeller bolt
- spacer bushing
- pump housing bolts

I know the bolts, impeller and possibly some other things are over-kill but I don't want to wait on another order if something is needed.

So anything I've missed?
Any tips/recommendations?

I'll be using Permatex blue as the sealer.
 

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If it has been years and years since the last rebuild, you can probably count on buying a new shaft, too. The pump housing bolts are reusable if they are not damaged.

Frank
 

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Discussion Starter #3
duckbubbles said:
If it has been years and years since the last rebuild, you can probably count on buying a new shaft, too. The pump housing bolts are reusable if they are not damaged.

Frank
Thanks Frank.
I doubt that the pump on this 66k mile bike ha sever been removed. I bought it at about 42k and the spotty maintenance records show only basic maintenance.
 

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The shaft will corrode badly. I've tried cleaning the corrosion and filling with epoxy to get a smooth finish will little luck. It's no fun to have the thing start leaking again rather soon. Best option is to bite the bullet and get a new one. It is also the large gear of the oil pump. Installing the water pump seal correctly is the hardest part. Make sure the mating surfaces are clean with no oil residue when reassembling. Don't get too over zealous with the sealant

Frank
 

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Discussion Starter #5
duckbubbles said:
The shaft will corrode badly. I've tried cleaning the corrosion and filling with epoxy to get a smooth finish will little luck. It's no fun to have the thing start leaking again rather soon. Best option is to bite the bullet and get a new one. It is also the large gear of the oil pump. Installing the water pump seal correctly is the hardest part. Make sure the mating surfaces are clean with no oil residue when reassembling. Don't get too over zealous with the sealant

Frank
Fortunately I have other Beemers to ride if mine is laid up for a bit so I'll wait to pull the shaft and take a look before ordering a new one at $193.10.

LIGHT coating of sealant - I've found chunks of sealant when doing coolant flushes on cars because whomever changed the water pump was from the "more is better" crowd.

thanks again
 

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Discussion Starter #6
Well… the first try did not go so well, it appears.

I followed all the recommended procedures; no corrosion on the pump shaft and used the bolt with washer technique to pull the shaft through the seal - still got leaks out the weep hole.

Any techniques or tips on why this may have happened or what I need to do differently the next round? I just got the new set today.

What still puzzles me is what appears to be some type of thrust washer that came out when removing the original seal. It seems to be part of that seal as there is no reference anywhere.

Off to an Airhead tech day this weekend, the brick will have to wait until next week.
 

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Discussion Starter #8
hfxrzw said:
Have a read/look here, mentions the spacers too.

http://hrsbstaff.ednet.ns.ca/bvogel/K100/oil_pump/oil-pump-seals-replacement.htm

Good luck, Rene

PS its not uncommon for the replaced seal to be leaking a bit. It sometimes needs to settle a bit so if it only drips some I'd take it for a good spin first before I change anything.
Thanks Rene, through the BMWTech list and much internet searching I came to the conclusion that my problem was probably the spacer bushing.

I now have a leak-free K75S!

The issue was the difference between the size of the spacer bushing. The second-generation water pump seal requires the new 10mm in place of the 14mm or it will leak badly.

That site is well done with great pictures.
 
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