Unofficialbmw.com

[robsure71]

I notice a cycling from under the dash. This is not present when the temp knob is turned to cold, but if I have the heat on and drive at 3,300 rpm, there is a sound from under the dahs similar to a diaphragm pump or door closing at about 60 cycles per minute.

I also notice that I do not have heat when I drive down the highway at speed. Will the water control valve on the heater close at a certain rpm? It makes no sound beleow 3,300 rpm, and certainly nothing above 3,500 rpm.

So, does this mean the valve I replaced two years ago is bad and needs replacement, or is a small part bad??