Q: Spongy brakes after replacing rear discs, pads and refurbing rear calipers. Bled so many times to no avail!

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Hi I have replaced the rear discs and pads on my Audi A3 8L after I had a sticky caliper. The dust seal was all chewed up and stuck inside the piston housing. I sanded the caliper down at certain points, cleaned and re greased and re fitted the caliper with a new dust seal and sliding pin seals. Whilst I was doing this I let the hard brake lines drip into a container as I didnt have anything to block them with. I have bled the brakes so many times using the one man, two man and compression bleeder method but neither seem to be helping. I have bled the master cylinder during these attempts and this also hasnt helped. Before using the compression tester with fluid i left it empty to do a test on the seals. Running 20psi I couldnt hear or see of any leaks from calipers or the master which leads me to believe the MC is ok? Unless that has changed in the bleeding taken place since. I have brakes but only at the very end of the pedal travel and very minimal. Any advice would be great!

My car has 175000 miles.
My car has a manual transmission.

All four wheels have to be bled starting with the right rear, then left rear, right front, and left front. Inasmuch as air may be trapped as much as 10 feet from the bleeder screw, you have to have a relatively fast, and substantial (in volume) flow of brake fluid during bleeding to expel all air from the system. Generally, 5 to 10 PSI on a pressure system is sufficient. 20 PSI is not necessary. You should use a power bleeder, they are not very expensive for a simple one. If you car is equipped with ABS and/or electronic stability control, you will need a VAG 1551, VAG 1552, or equivalent bi-directional scan tool that is capable of activating the ABS/ESC pump. Activation is necessary to expel air from the ABS components of the system. If you would like to have this checked, a qualified professional from YourMechanic can come to your location to inspect the spongy brake issue and let you know what needs repair.

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