Master cylinder going bad?

[trivalence]

About a week ago I put new pads, rotors, and calipers on my Legacy. The brake pedal travel had been a bit troubling, going fairly close to the floor. I was hoping that bleeding all four wheels would improve it, but it hasn't. Now the only thing I can assume is wrong is the master cylinder. Does this sound accurate? I don't really know what role the brake booster plays, but I'm hoping it's not the issue.

 

At one point the other day I was sure that if I pushed hard on the pedal (while stopped) I could hear a noise like air escaping or a high pitched whistle or something. I haven't been able to replicate that again, however.

 

Stopping power doesn't really seem to be affected, so maybe I can just leave it as-is until ... whenever?

 

 

[lmdew]

When you bleed the brakes, you should not let the brake go down further than it normally does.  Putting a 2x4 on the floor usually keeps it in a safe zone.  

 

If you take it all the way to the floor, the piston is working in an area of the cylinder that may have built up crud and it can take out the seal.

 

I'd try bleeding it again.

If you pump the brakes do you get a better feel?  Then air in the system.

[idosubaru]

bleeding like he said, try it some more.

 

the one hard to diagnose pedal travel subaru i worked on ended up being a pin hole rust leak in the rear break line. i didn't figure it out for a couple weeks as it was enough to bleed off pressure but not enough to spew enough fluid to run down off the gas tank.  it was above the gas tank so fluid was just collecting/splattering up there and not reaching the ground where i could see it.

 

if you have rust underneath - you might want to check those lines.

 

master cylinder failure in subarus is very rare - not impossible but they are robust and not prone to failure.