algie928s4

I overhauled all 4 calipers a short time ago, sent out for powdercoat and new piston gaskets / dustcovers, also added stainless braided to calipers, re-assembly went smoothly and bleed from furthest point rear to front as procedure.
However both rears are barely operating, enough to prevent disc surface rust but no real bite, I've bleed repeatedly now suspecting a some air trapped somewhere but no improvement and used a twin non return valve system for bleeding, all went well, I pulled 2 litres through the 4 calipers today with not the hint of any air in the system- and no sign of any leaks anywhere.
Anyone got any ideas, I know theres a brake valve which sets braking pressure front to rear, but as it was all working fine before overhaul, banging the old head time!
I've got an 89S4 auto

JHowell37

Did you try bleeding them the old fashioned way. That means get a helper to pump the brakes while you open and close the bleeder screws. I've found that gadgets like pressure bleeders are fine, up to a point. But to really bleed them, you need to do it old school.

Jim bailey - 928 International

Note there are two bleed screws on the top of each caliper and BOTH need bleeding.

Mrmerlin

did you bleed the master cylinder first?,
Is it possible that the hard line to the rears got crimped,
could the powdercoat have gotten on the bores of the rear calipers? Since everything is clean did you find that the rear pads have a bit of clearance when they are seated as opposed to having the pads binding.
Are the rear caliper seals the correct ones for the calipers your using?

algie928s4

Thanks Jh and Jim, I've bleed these brakes a few times now, 2nd last time I even tried tapping the calipers with a rubber mallet during bleeding to insure there where no air traps in the calipers, the bleeding is 100% ,there has been no change from the initial bleed from the install when I was aided by two fellow 928'ers.
Jim is there any tests for checking the brake valve or the ABS control unit?