i did a caliper swap on the vette - 1991 - fronts only. i had each hose off for about 20 seconds, reconnected and opened bleeders to gravity fill the calipers before bleeding them via mityvac and then by the make your wife sit in the car and pump the pedal method.
i have a spongy pedal that goes to the floor slowly while holding it. i have never had to bleed the rears on any car with just a front caliper swap. i am getting no air out of the fronts at all - and am going to bleed the rears to rule that out - but what could i be overlooking? no leaks at the fittings or hoses, and the only part of the system disturbed was the hose to caliper connection. i've been bleeding brakes for years from simple repairs to building complete systems from scratch and never have had an issue like this.
Slow pedal drop often indicates bad master cylinder.
Had the same problem recently with my urq, changed the rear calipers only and then couldn't get a good solid pedal no matter how I bled the system, vacuum, pressure bleeder or wife.
Turns out the master was bad, most likely from the bleeding by wife pushing the internal seals past their normal ( while operating with good brakes) range of travel and causing the seals to split and causing internal pressure loss.
Supercoupe wrote:
Had the same problem recently with my urq, changed the rear calipers only and then couldn't get a good solid pedal no matter how I bled the system, vacuum, pressure bleeder or wife.
Turns out the master was bad, most likely from the bleeding by wife pushing the internal seals past their normal ( while operating with good brakes) range of travel and causing the seals to split and causing internal pressure loss.
yeah i'm leaning this way with the more research i do.
ugh - $135 master cylinder is not affordable right now - maybe i can find some cash on the ground somewhere.
Yeah, I know the feeling, took mine apart, found the seals looked good but the cups split around the shaft, tried to get a rebuild kit but it seems they don't exist any more.
Lucked out with one for just over 100 though from Autozone and they had it for me the next day.
i'm used to $12 70's gm cast iron units, not this fancy aussie PBR stuff.
as i did not get any air out the last 4 times we bled it yesterday i'm going to just order a master and go at it when it arrives as i'm sure there is no more air in the system.
This may/may not be applicaple to your calipers:
Calipers should always be installed with the bleeders up.
Installing them 'bleeders down' will make it very difficult to bleed out the trapped air.
It's easy enough to check/fix.
thats hopefully common sense. 
Duke
SuperDork
7/5/10 1:59 p.m.
So you should tell your wife to only push the pedal halfway down, not to the floor?
Do the rears have a proportioning valve?
