You will need to buy a new rear cyclinder seal kits are no longer available, this is what is needed if your car is on shoes. If your car is on Discs then it is more likely that the caliper seals have perished and will either need to have the calipers reconditioned or buy new ones. Seal kits are being made obsolete as the manufacturers of them can no longer stand the insurance needed.
dave, August 2007