Hello all I've got a early 2v k100 as we all know they run very warm. The bike has only 17k on it and the pump is sporting the old impeller.  My question is does the new kit with the new style impeller more efficient in the job of keeping the heat down or is it a case if it ain't broke don't fix it............??

Flush the cooling system and make sure there aren't a lot of bugs and dirt clogging up the fins in the radiator. Refill with a 60% water coolant mix. Don't mess with the pump unless there's water or oil coming out of the weep hole.

A little story for you, Jibe, about what happened to me. 

I added a coolant temp gauge to my bike in July 2020 which required removing the pump cover to run the wiring, etc. My bike had the old style cast iron impeller and nut. The nut was still attached.

My final ride was early October that year. I had already decided that part of my winter maintenance was to upgrade my water pump with the new style impeller instead of waiting for it to potentially fail, leaving me stranded with possible damage to also contend with. It wasn’t leaking either coolant or oil. I had ridden about 3,700 miles in 2020 on my bike which put the odometer at 33,779 miles when I parked it for the season.

After draining the coolant and then removing the cover in December, KERPLUNK! I just knew what it was. I looked at the impeller and the nut was gone. It took a swan dive. So sometime between July and my last ride in October of last year the nut had broken off and I didn’t know about it. The impeller was still firmly in place. I got lucky.

Point-Seven-Five’s comment about leaving stuff alone is valid. All I can say is that my approach to preventative maintenance most certainly saved me from more problems and maybe a tow truck ride home.

I have no idea if the new impeller improves coolant circulation and, therefore, cooling. The whole reason behind doing the upgrade was due to the fact that I didn’t have peace of mind knowing that the original components were prone to failure which is why BMW changed the design. 

What I will say is this. If it doesn’t bother you, leave it. If it does bother you then do something about it. Pretty low miles on your bike. You could go for eons without a problem.

Was thinking maybe new waterless coolant might be an option. Understand its not supposed to boil & helps prevent rust & corrosion as it is water free?.

poddy wrote:Was thinking maybe new waterless coolant might be an option. Understand its not supposed to boil & helps prevent rust & corrosion as it is water free?.

Using this for years on BMW, ready to use coolant.

https://www.mpmoil.com/products/view/81000/coolant-26%C2%B0c-ready-to-use/nl?region=kr&%3Blanguage=en

I'm gonna make it a winter job. The coolant went in a few months ago and I know its a rusty brown colour. Needs a good flush out and clean, the oil is good though. I guess we are called enthusiasts because we want the old girls still running tip top

Jibe wrote: I guess we are called enthusiasts because we want the old girls still running tip top

By your definition, an enthusiast wouldn't run a moto engine with coolant having definite signs of corrosion that would not only degrade the pump but also affect the ability of the coolant to absorb heat from the engine.

Jibe wrote:I'm gonna make it a winter job. The coolant went in a few months ago and I know its a rusty brown colour.

Your coolant is rusty and you want to know why your engine runs hot??? If it was my bike, a good flush wouldn't be a winter job.