Try putting your hand on the pump and see if the buzzing is at the same frequency as the vibration. Another way is to stick a screwdriver handle in your ear and press the blade against the pump - a make do stethoscope! All pumps will buzz to a certain extent - its made worse if there is air in the system. Check that there are no other parts touching the pump as this could amplify the noise. Noisy pumps do get worse eventually but it usually takes some time. If you are sure that it is the pump making the noise you can leave it alone.
John, December 2007
