You do not want to mess with the timing belt tensioner! Don't try repairing it in any way. Too much damage can be done to the pistons and valves if it fails and allows the belt to slip on the cam gears while the engine is running. You'll end up with a very big repair bill, rather than the $100 or so that a new belt tensioner will cost you. Put in a new belt tensioner and don't mess with the old one.