I have done this to three of my 140's over my Volvo career and have had great results. From what I can tell the calipers are the same just that the 164 calipers are slightly wider it the bridge where the to halves of the caliper come together to accommodate the wider rotor. I don't think the caliper holding more fluid is your problem. I have always a pressure bleeder like the one IPD sells, a great investment! I would try to get your hands on a pressure bleeder, bleed in the order that the manual tells you and did you change out you old rubber brake lines? This can give you a mushy pedal also. For what its worth I hope this helps.