jaundice

Get a power bleeder. Makes short work of this problem.

realblag

The hiss noise you hear is the vacuum assist, aka the booster, doing its job.

rob-2

I think so. Talk to billman I think you are going to have trouble getting the air out of the abs as its not engaged when doing a normal bleed

SpitfireS

OP: did the master reservoir run dry during the caliper swap?
If so: air in the system.

I've wondered more than once about the ABS pump and how it would handle running out of fluid.
As there is no special tool to activate the seperate solenoids and run the ABS pump - to simulate ABS - during bleeding I think the ABS unit is designed to not trap air in the small reservoirs if it runs dry.
A new, out-of-the-box ABS unit is dry too, I wonder how they bleed it without any special electronic activator.

Maybe it is best to do brake work / caliper swap in winter.
After the swap its easy to activate ABS on snow or ice and re-bleed

OneSilverS2k

Make sure the bleeder valves are facing up, I once put the front calipers on the wrong side. Air gets trapped in the top of the caliper that is why bleeder valves are on top to get rid of the air.

S2K.Danny

Any update on this? Just replaced my rear calipers & am going through the same thing & the air bubbly noise from the booster/master cylinder doesn't sound familiar from the last 18 months of owning the S

wherezmytofu

oh problem solved, i put the calipers in the wrong way, left in right right in left since i grabbed them off ebay for $25 shipped the dude sent it to be marked them the wrong way

quick fix is, air bleed is always on top or else it will never bleed properly