You need to drain the atx. Spring should be fine unless you visually note cracking, etc.
You have to pull the servo piston out and see how many rings on the shaft. You order by number of rings....of course you don't know until you pull it out and once it is out you then need to order and wait for shipment. What you could do since the servo cover is so cheap. Buy two. take off the old one and count the rings. assemble back together with new cap. Order new servo piston and then take apart again when it arrives. Spare cap is in case you bend cap, leaks, etc.
Bob
