I have a couple of old Olds Ambassadors. The first valve on one of them start to "whistle" when depressed. the valves in this trumpet were older, worn and had rust stains on them. I changed the valve with another horn -- good condition, plating good -- the whistling stopped. It worked BTW). when i put the older valve in the other trumpet, it whistled. obviously the problem is the valve. what else could cause it? does this mean the whistling valve is no good? Hardly worth replating.