hi,
ive just recently changed the bov on my car to a sheepdog bov and am having trouble getting it to make a sound.ive tried all the basic things like adjusting the spring,putting in a small drop of oil.ive also had someone look at the bov when i rev the car and the piston opens but no sound.is it possible that the piston is worn out?how can i tell ?can it be repaired ?

thanks,pete.