This is generally regarded as a sign of a pending failure of the check valve, and probably correctly so....however, mine "buzzed" all last summer without failing. When I got home and removed the valve, I found a few pieces from a valve that failed a few years ago, stuck into the ilnlet side. Removing them fixed the buzz.The valve has performed flawlessly for 6 months now, SO..., Failure isn't automatic, but I'd recommend a look see, if no debris, then I'd say, replace it. If you can find a good one, one with steel "insides" I'd say, replace it , debris or not...rgr...
2004 Winnebago 33V, WH
2010 Honda CRV
Jim, Lynda, and our 6/2010 model Weimaraner, Quincy, aka Q Man