My experience is that compressed air up to 100 psi won't even look at them. Push them out hydraulically - that's how they are intended to work. You can simply fit it to the car -and press the brake pedal (after blee
ding out any air). If that doesn't work - I have used a grease gun in the past - obviously you need to make up a connection from grease gun end (mine is 3/8" UNF) to the brake pipe inlet which is 10 x 1 metric. Then just pump in grease and the pistons WILL move outwards. If one piston moves more than the other - clamp it so the other gets some exercise. Eventually both will be moving easily - pump until one of them pops out, and then hope you can wiggle the other one out too. The whole lot now needs careful cleaning to remove ALL the grease before re-assembly. Note the caliper pistons are same as Classic Mini (84 -2000) - and stainless pistons are readily available, which don't rust in future!
