Thread: Disco 1 spongy brakes after pad inspection

Originally Posted by ROAMER_AUS

Hi all!!!

Pulled out my brake pads for inspection 2 lhs wheels as I had some noise while braking. To put them back easily, i pushed cylinders back. Now I have spongy brakes. I've done this many times before without these effects on different types of cars. Is there anything special about Discos that will get air in the system by pushing pad cylinders back?

Thanx!!!

not usually but they do have an occasional habit of sticking the piston seal and the bias valve.

Originally Posted by Blknight.aus

not usually but they do have an occasional habit of sticking the piston seal and the bias valve.

Thanx Blknight!!!

Still, I don't know how this can cause spongy brake. As far as I know spongy brake means air in the system. If piston seal is gone, I should see some brake fluid leaking, there is none.

Bias valve, I'm not intimately familiar with it's operation, but still can't figure out how it can introduce air in the system.

Originally Posted by ROAMER_AUS

Thanx Blknight!!!

Still, I don't know how this can cause spongy brake. As far as I know spongy brake means air in the system. If piston seal is gone, I should see some brake fluid leaking, there is none.

Bias valve, I'm not intimately familiar with it's operation, but still can't figure out how it can introduce air in the system.

they dont...

your breaks feel spongy because the piston seal is pulling the piston back too much so you have to travel further before they pick up.

the bias valve if it gets stuck just slows down the transfer of fluid to the back brakes making the pedal feel spongy

you could have also over travled the master cylinder on the first application and the internal seals are now damaged allowing it to recirculate the fluid.