Hi. You didn't say "how" you bled the system -- i.e., whether you used the "step on the brake pedal" method, or used some sort of "pressure bleeding" device.
I know you're a regular on this list, and might therefore have read at least once per week cases of people using the "step on brake pedal" method ending up with a bad master cylinder, so I hope you used the pressure bleeding method instead.
If you didn't, that's probably your answer -- in stepping on the pedal with a bleeder open, you stepped down too far, and pushed your m/c's piston too far, destroying the seals. Thereafter, you m/c is shot! Get a new one.

IMHO, Volvos should only be bled using a pressure bleeder. For next time, IPD sells a nice new "tank" (complete with pressure gauge and hand pump) that connects to the master cylinder -- I used it, and promptly through away my older device that relied on a spare tire's air pressure. This new one is great!

Hope this helped solve the mystery.
Best regards,

Assuming the first total system bleed was good, AND you didn't lose fluid all the way back to the MC (blocking the brake pedal down an inch or two will prevent that), I would just bleed the replaced caliper.

But if it's an off the shelf rebuilt, it may have mis-matched halves, as spotted here a couple of times recently. Her's my "canned post" on the subject:

1 — In the Girling 4-piston calipers, the upper two piston chambers basically form an inverted U, with ONE common bleeder at the highest point.
The lower two piston chambers form an upright U, with bleeders at each of the TWO high points.

2 — Rebuilders sometimes get the INNER and OUTER caliper halves calipers mismatched. (i.e. The Left Side INNER half, where the lines attach, will have a Right Side OUTER half paired to it — but that OUTER half will be upside down.

3 — During the original assembly, Girling distinctly marks the bottom of each caliper half with a "dimple" mark next to the joint. So a mark on the TOP of an OUTER caliper half means a mismatch.

4 — Such a caliper will have:
A - No fluid path to the Upper-Outer cylinder
B - No way to bleed the Lower-Outer cylinder

What appears to be the normal Outside piston bleeder actually leads upward to a dead end, at what should be a lower piston chamber.

And the (misplaced) Lower-Outer chamber has no bleed path except down and then up to the Inside bleeder.



--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

you bled the whole system...THEN...changed the caliper and didn't bleed the WHOLE SYSTEM after you exchanged a major component. Try bleeding the whole system