Brakes hard as a rock after bleeding

[Jeff R]

I semi-successfully bled my brakes finally, using Mobil 1 ATF. But, I have issues. The main issue is that the brakes feel extremely hard. It is like the system is locked up. No, the parking brake is not set, but the pedals will only move a little bit. The reserviour is vented so I don't understand why all the brakes, both left and right and passenger side and pilot side, are so firm.

I am thinking that the brake pistons are pressurized and not relaxing. In bleeding the left side, in particular, I had a lot of trouble. I had removed the brake from the wheel and tried bleeing it that way, and the piston came out and later, even after I removed the bleeding plug, it would not retract until I wedged a screwdriver and forced it. It seemed to me that the brake was locked up irrespective of the bleeder valve being off. How could that be? I put it back on the wheel and got fluid to flow upwards and thought all was well, but now both brakes are hard as a rock. There are some air bubbles in the line between the two master cylinders on the pedals, but they only move an inch or so when I press down hard on the brakes. The pistons appear to be firmly up against the brake pads.

Any ideas?

[Mike S]

Are the pushrods in the master cylinders all the way out???

[Sam Buchanan]

Originally Posted by Jeff R

I semi-successfully bled my brakes finally, using Mobil 1 ATF. But, I have issues. The main issue is that the brakes feel extremely hard. It is like the system is locked up. No, the parking brake is not set, but the pedals will only move a little bit. The reserviour is vented so I don't understand why all the brakes, both left and right and passenger side and pilot side, are so firm.

I am thinking that the brake pistons are pressurized and not relaxing. In bleeding the left side, in particular, I had a lot of trouble. I had removed the brake from the wheel and tried bleeing it that way, and the piston came out and later, even after I removed the bleeding plug, it would not retract until I wedged a screwdriver and forced it. It seemed to me that the brake was locked up irrespective of the bleeder valve being off. How could that be? I put it back on the wheel and got fluid to flow upwards and thought all was well, but now both brakes are hard as a rock. There are some air bubbles in the line between the two master cylinders on the pedals, but they only move an inch or so when I press down hard on the brakes. The pistons appear to be firmly up against the brake pads.

Any ideas?

Sounds like you have successfully bled your brakes.

There will be very little pedal movement. Jack up the wheels and make sure they rotate more or less freely without the brakes applied. If the wheels are free until you apply the brakes.......well......that is what brakes are supposed to do....

The pistons will maintain very light contact with the rotors. This is normal. It would be nice if the bubble between the cylinders could be bled out, but if you have firm brakes that work properly, this isn't a deal-breaker.

[Jeff R]

Thanks. I was expecting more brake travel but I tested things out. I could move the fuselage and, when I sat the parking brake, it wouldn't budge.

So, yeah, I am done!