I had what gumby1 is describing happen with one of my walkers about 8 years ago... Turned out to be a burned up hydro from poor maintenance by the previous owner. Since then... I change my gear and hydro fluids EVERY winter and have never had a hydro burn up on me since! I have a question though... Are the Hydros left and right OR are they the same unit on each side (just turned around). Still have that one on the shelf to get rebuilt if I ever find a place that will rebuild it for me.