Hello All,

This weekend I replaced the pads and rotors on all 4 wheels of my 04 S80 at 202K miles. On test drive, right front caliper won't release from the disk (everything is hot). I replaced the caliper and hydraulic hose then bled the system buddy method, RR, LR, RF, LF. Test drive and new right front caliper won't release. Brake pedal very soft. No malfunction lights.

I hear an occasional hiss under the hood, like when you unscrew a soda bottle cap. Lots of pedal resistance when car is off, very soft when car running.

What do you think? Master cylinder? brake booster? Vacuum line?

Thank you for any advice!

 

I would take the caliper off put a spacer like a piece of wood between the pads to simulate the disc and cycle the brakes to see if it clamps and unclamps. Don`t push on the brake pedal with out something between the pads or you will push the pistons out and have a real mess. If it stays clamped the that caliper is suspect. New rebuilt ones are prone to not being all that great

 

Thanks thommykent, Although anything is possible, what are the chances a new caliper would do the same thing as the old one?

Has anyone ever heard of a failed brake booster or master cylinder causing a caliper to stay clamped?

 

Not that likely, but it`s easy to check. If when you bled the brakes you pushed the braked pedal to the floor, it can foul the seal in the master cylinder, but that would effect all 4 then. I would loosen that bleeder screw on the caliper in question and try to push the pads back. They should go back easily. If they don`t the caliper has a problem.

 

are you getting and releasing pressure? wondering if it could be a stuck ABS valve.

 

Thank you Thommy and MT. Well this is kind of embarrassing but here's what it was...

The wheel that I thought had the caliper not releasing: was just warm for no more reason that new systems get warm. The backing plate behind the rotor was touching the rotor, causing a hellish noise, sounding like it was almost seized/not releasing. First problem solved very simply.

The soft brakes: The first tip off was that I replaced all 4 corners. The second was that the brake pedal was firm while car not running, soft while running. The third was that the soft brakes didn't exist prior to doing this project. This turned out to be caused by my installing the caliper clips incorrectly. If they go on easily, you probably installed them incorrectly. The ears at each end should be below the assembly at each end. In the incorrect installation they were pulling each caliper open after releasing the brake pedal each time.

There are other posts that describe this issue I had to search hard to find. I hope loading this up with keywords makes it find-able for other noobs.

Peace!

 

Thanks for the update