Clean Coolant Coming from Weep Hole

[MichaelMandel]

OK.... So I came upon a 1985 k100RS that my buddy up and gave to me.  I've stripped the plastics off and noticed the fan never kicked on.  I took out the old thermostat and before putting the new one in I decided to leave some good old fashioned water in to flush it out before popping in the new thermostat and proper coolant.  After letting it sit in the heat for a bit after riding it hard on a 100 degree day the fan finally kicked on.  After riding it like this for a week or two I am about to pop the new thermostat and coolant in when I noticed a leak trail up my driveway.  It's water(in place of coolant)... and it's coming from a weep hole I discovered on the bottom side of the pump housing.  It's clean water from the cooling system and there's zero oil in it and the oil is a perfect golden color and free of contamination from the cooling system so the seals are good.   What's up??? will popping the thermostat in correct a flow issue and get rid of the purging from the weep hole? is straight cooling system coming from the weep hole a super bad sign if not contaminated?  what's up???

[F14CRAZY]

In the oil/water pump there is a ceramic seal for the coolant and a neoprene lip seal for the oil. They're separated by an air gap which is what the weep hole is connected to. Mixing them is possible but not very likely.

There are a number of threads on replacing the seals so try a search. It can be frustrating but it's possible

[Scott_]

While you were riding it with the straight water, did you get any transfer to/from the overflow tank under the seat?
Reason I ask, I'm questioning the radiator cap pop off. If the cap failed it's potentially possible to push the water out the pump seal.
Not likely, but still something to investigate before you strip your pump off.

[MichaelMandel]

I'm not sure about radiator cap or overflow reservoir but I'll check today. Something tells me there's no liquid making it  cap and into reservoir.  I am going to put the new thermostat in and run it with water and see if the weeping goes away but what is the likelihood of that? Anyone know where I can find a new radiator capcap for a k100? Probably worth replacing first right? So it is possible for a temporary cooling system lrak that will fix once pressure and flow is corrected and back to where it should be right? I mean running without thermostat alone changes everything, not mention the expansion of straight water.  It never seemed before I did this so I hope run into straight water and no thermostat for a week could permanently damage the  in pump...

[Jnclem]

You can get a new cap, or just the two rubber seals that go inside the cap, from BMW. The two seals are cheap, and usually all that's needed.

[MichaelMandel]

How so I get them from BMW? Call the dealership?

[MichaelMandel]

...also, there is coolant making it to the overflow.

[Jnclem]

How so I get them from BMW? Call the dealership?

Yes, or order it online. I usually go to the parts fiche at Max BMW online and get a part number. Then, I either order from my nearest dealer, not very near, or from Max or Bob's online. Here is the page for an '85 K100RS cooling system http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51752&rnd=07012015.

The whole cap is part number     17 11 1 464 720, and the two replacement gaskets are right above that,     17 11 1 464 319, and  17 11 1 464 759.

When I got my LT, the cap was bad. I replaced it with a new one, but I also got the gaskets for next time.

[MichaelMandel]

I've now moved on to pretty much knowing I have to redo the water pump  since the entire cooling system emptied in a matter of hours out of the weep hole.  Is it possible to simpy pull the pump housng and redo cooling pump seal without oil seal if that is fine?