How do you replace the hydro pneumatic unit (P/N 857 612 085 A) -aka the bomb-? I see no bolts or anything on the exploded view in ETKA, just one single O-ring. Any BTDT precautions removing/refitting this nitrogen bomb? Thanks Regards, Maurits 1986 GV (Swiss WR) 1985 CGT KV 1982 GL DD