E34 Heater valve / aux water pump cycling ??

[Super90]

I keep hearing either one of the heater valve solenoids or the aux water pump cycling off.........then on.............then off..........then on.

Was pretty noisy, so I just changed the aux water pump. Seems quieter, but still cycling. Tried to figure out which item it is, but too hard to tell. I have owned the car for about ten years and never noticed this cycling, but was never listening for it.

Is it supposed to work like this? Should I replace the heater valves? Or is there some control unit that has gone bad somewhere else?

TIA

[Paul in NZ]

is it a regular "thumping" that you really only hear when stopped at a traffic light or similar?I a prety sure this is a sign of "sticky" heater valves.my car started doing it then i had a period when my heater would come on at times of its own accord.I could ussually get it to beheave itself by cycling the temp wheels up to full hot and full cold a few time.I gave the valves a good tapping one day and ll was well,but i have noticed the noise is back.

[shogun]

heater valve testing
http://www.bimmerboard.com/forums/posts/380566/
yoy can easily find out what is making the noise, unplug the connector from the heater vales, no power = full open. should not make noise. Unplug the connector for aux water pump, pump without power = no noise.
http://bmwe32.masscom.net/johan/watervalves/watervalves.html

Some related links
http://www.bimmerboard.com/forums/posts/425604/

[John 535is (Sydney)]

After you do Shogun's check, if its the heater valves you can purchase new solenoid parts sperately rather than puchasing a complete heater (much much cheaper). JM