I just finished rebuilding the servo on my 59 XK 150 OTS - Are you able to do the work yourself? The only thing that I need to repair was the vacuum chamber. Top was pitted where piston rested for years. Was able to clean and fill pits w/ an epoxy based metal filler. The piston seal is leather which was restored with leather treatment. I don't know this for sure but have been told pistons came also were supplied with a rubber seal as well. The hardest part of the job is getting the hydraulic cylinder apart, takes soaking and patients. Found a product call "Metal Recuse" comes in gallons bottles. Can get @ Home Depot, Walmart, Menards. It is a bath in which parts need to be submerged and soaked for 4 to 24 hours. Does a great job of removing rust without remove good metal.
