1985 K100RS sheared water pump impeller nut.

How fortuitous am I! Winter maintenance includes upgrading the old style cast iron water pump impeller to the new style so that what I just found wouldn't happen. I had the water pump cover off in July to run the temp sender wire as I installed a coolant temperature gauge. Everything was fine then. As soon as I popped off the cover, KER-PLUNK! I knew exactly what it was as soon as I heard it. No damage luckily.



Updated my post with image of the shaft below. Though corroded, it wasn't leaking. The top three bolts of the pump housing decided to be difficult. I had to remove the front wheel so I could get a good swing with a hammer at the impact driver, all while chanting a frequently used expression by The Borg. Tomorrow I'm off to see about getting the housing and pump cover power coated and then everything back together with stainless steel hardware.

Not sure if it helps, but 98lee has a link to water pump rebuild info in this thread...look for the specific post:

https://forums.bmwmoa.org/forumdisplay.php?54-K-bikes-DIY-Tech-Library

Yep been there done that old style water pump. Bummer, but they crystalize and break easy. Never had a K bike I didn't have to replace water/oil pump on.

20774 said:

Not sure if it helps, but 98lee has a link to water pump rebuild info in this thread...look for the specific post:

https://forums.bmwmoa.org/forumdisplay.php?54-K-bikes-DIY-Tech-Library

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Absolutely! Thank you.

mcmlcccvrs said:

Absolutely! Thank you.

Click to expand...

I remember taking off my water pump off my 85 K100RS with 150k miles and having it rebuilt due to leaking.

Water in the oil mixed: first sign on trouble in my 85 K100RS

The first shaft design ('85) used the nut on a stepped shaft, this is weaker than the second design, a tapped hole in the shaft with a bolt down inside the shaft. A step in a shaft is a weak, stress rising point. A tapped hole is strong. The updated setup will fit in your '85. It is the way to go and then clean out the radiator of oily goo and your overflow tank. I think I posted my whole story about this, years ago, when I turned around on a Sat am 15 miles from home on a trip to Maine. Took bike apart, drove a car to Bob's, shopped from 9:30 to 11, drove home did the update, test rode to my son's 6 pm baseball game and went to Maine the next am, 24 hours late on a 10 day trip. Mine had not yet broken but the stepped part of the shaft stretched enough to blowby the oil/water seals.

I had to confirm my memory on this interesting process-

I've been researching this topic today with some interesting results. Anyone using Cascade Dish Washing Detergent for a radiator flush? Most swear by it and some are against it. Highly recommended on the CAT Cummins Diesel Forums for removing oil from the cooling system. Some CAT Dealers even have a part # for it! Some use the liquid but most prefer the powder mixed with distilled water. Main Ingredients-Sodium Carbonate, Sodium Silicate and Enzymes

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Cascade with boiling water is also great for cleaning out the coffee remnants in your thermos.

https://www.steelsoldiers.com/threads/radiator-flushing-with-cascade-dishwashing-detergent.58868/

OM

I have some water pump info on my website: http://largiader.com/articles/waterpump/