The Girling on my 740 is a 2 piston per caliper type. One piston is dificult enough, imagine doing 4 pistons at a go. My mechanic was swearing by the 3rd piston due to the same problem you encountered. Problem here in Malaysia is I can't yet seem to find rebuilt calipers as described by fellow brickboards in US. The mechanics I've asked says they have to rebuild it themselves. Hence the quality I guess varies. The seals and boots etc are readily available though. Anyway thanks for your input. By the way if you had to do it again would you rebuild it again or get a rebulit caliper?