Thanks Dan for your advice. Even after several more bleedings the problem persists. I had changed rear calipers on my '85 245, and bled the whole system several times, yielding good hard pedal with the engine off, and the brake booster not under vacuum. The pedal is just as hard after sitting all night, with no pumping. When I start the engine, the pedal falls more than normal, feels spongy, and can gradually be pushed floorward. Significantly, on releasing the pedal, the engine stumbles as if from momentary vacuum loss, something I've never encountered in 20 years of owning Volvos. I did the FAQ booster test with no clear results. The big question is whether hard, no-creep pedal with engine off and booster vacuum bled down means the hydraulics are definitely sound. The dealer says it's still possible for the master cylinder (only 18 mos. old, and flushed 12 mos. ago) to be bad, since one would have to push very hard to feel any creep without booster assist. I wonder about this, and would also expect the brake failure light to come on with disproportionate pressure at the junction box. The engine stumble suggests the booster, though the one line to the manifold, and the check valve, are fine. It's got me feeling downright stupid, and I'd be glad for more advice. Thanks!!