I've had my fabulous Kurt Kinetic fluid resistance trainer for three-ish years now, and it's been wonderful, except the last few weeks it's been making burbling noises like there's air in the resistance unit or something. The resistance may or may not have gone down, I can't really tell as I changed my gearing at around the same time. I have not found any fluid or residue on the floor (I've been looking for it). Is this just an issue of the resistance unit getting old? Anyone had this problem?