Water-Oil Pump Change '93 K75S

[ghyber]

Can one assume that after a water/oil pump rebuild changing the oil + water seals, that it may take some engine running time for the seals to settle into place and provide a perfect seal? I ask as I have been getting to coolant drips through the front weeping hole.

[roncooper]

I had no drips after the dealer rebuilt mine.

[kentuvman]

From the posts I've read, the rebuild can go South and the pump will leak after a rebuild. I called a dealer and the service manager declined the work - he said from his experience it was easier just to buy a new pump. I figured I'd buy the parts, give it my best shot, and if it failed, I'd buy a new pump.

In my event, I bought my parts from Motobins and had to also buy a new impeller compatible with the new seals in the kit.

I did find some YouTube videos on rebuilding a K75/K100 pump, watched it and watched it more than several times before the rebuild. For me, I guess I'm lucky as the rebuild was successful.

It may be back to the drawing board.

[rdalland]

FWIW - No drips after I rebuilt mine ('95 K75RT).

[ghyber]

Thanks for the input guys, they are all really appreciated.

FWIW, how do you know the pump did not leak at startup while at the dealership? The dealer probably made a dry run for 10 or 15 minutes where the bike may or may not have had oil/coolant leaks before handing over the motorcycle back to the client.

I had some coolant drips and a little bit of oily residue yesterday. My take is that the oily residue is probably a result of the grease which I used to help when inserting the shaft through the new seals. The residual grease probably heated and funnelled its way down the weeping hole. The coolant short lived leak may be from one of two possibilities, the water seal had not seated and coolant made its way in the air chamber while refilling the radiator and/or the drips were from spilled coolant on the engine during the refilling process.

I am still optimistic that I performed the task flawlessly. But when Paul Glaves says that his batting average is 50/50 when replacing these seals, and his talents are without a doubt better than mine, my concern is somewhat warranted.

However, the K75S sat in my garage overnight and after running it at 5200rpm/110km/h, there are no obvious signs of leaks on the white cardboard box under the weeping hole.

Today, I will test ride with a 200km trip, that should provide me with better sampling.

[ghyber]

From the posts I've read, the rebuild can go South and the pump will leak after a rebuild. I called a dealer and the service manager declined the work - he said from his experience it was easier just to buy a new pump....

That's a very independent and nonchalant BMW motorcycle dealership considering BMW motorcycles are easy to work on and built to last a very long time with many rebuildable components, like the water/oil pump.

[kentuvman]

That's a very independent and nonchalant BMW motorcycle dealership considering BMW motorcycles are easy to work on and built to last a very long time with many rebuildable components, like the water/oil pump.

Actually, it's probably the most favored BMW Dealer in the state of Minnesota. The service manager probably figured it's easier and more profitable to sell a new part with a warranty than rebuild a pump that has a 50/50 success rate and then have the customer come back and saying "my pump still leaks."

Sadly, we live in a throwaway society. I always try to fix something broken before replacing - too many people think otherwise.

[roncooper]

I removed the pump,the dealer rebuilt it and I reinstalled it. No drips.

[58058D]

Same here, many many years ago. Removed by me, rebuilt by dealer, reinstalled by me. Both the K100 and the K1100RSs. The K12RS pump has not leaked.

[deilenberger]

ghyber,

Rubber seals rarely seat, but the water seal on the K water pump is an odd one, it's a spring loaded graphite seal. Unfortunately it's easy to misinstall.. but they also have been known to "wear in" and seal themselves. The rubber seal is on the oil pump side of the pump.

Also - http://www.bmwmoa.org/forum/showthread.php?t=46057 - I'm adding that info to the thread title.

[ghyber]

Test ride completed successfully, oil/water pump housing and crankcase area dry as a bone. I think I can breathe now and give myself a tap on the back.

I purchased the BMW tool for driving the press-fit water seal and it helped a lot. I am in Montreal, Canada if anyone wants to borrow the tool or needs help rebuilding seals.

I found the biggest challenge to be driving the stubborn old seals out of the pump housing without gouging the cylindrical walls where the shaft inserts; need one of those funny screwdrivers with a 90 degree hook on the end.