A quick "fix" for spongy brakes

[PerryC]

I had been getting very frustrated with the brakes on my '11 forester. They went almost to the floor and felt very spongy. I replaced the master cylinder and blead them a couple times with no improvement. Then last night I tried something radical.  I adjusted the brake pedal. It only took about 10 minutes. I pulled the pin that connects the pedal to the brake booster connecting rod, loosened up the brake light/pedal stop and unscrewed the U bracket on the end of the connecting rod about 3 turns. There is a lock nut behind it. Then I adjusted the pedal stop the same amount. This moved the pedal away from the floor about 3/4 of an inch farther.  I had to do a bit of adjusting to make sure that the car still rolled and the brakes were not locked up. When I got it back together and did a test drive OMG it was like brake Nirvana. Sure, you have to move your foot a bit farther to get from the gas pedal to the brake pedal but the brakes now stop the car at a level that feels normal and it is much less spongy feeling.  Amazing how such a small adjustment can make a BIG difference.

[1 Lucky Texan]

has the car always had this problem?

 

what brand/type pads are on the car? no stuck calipers?

[PerryC]

I bought the car 6 months ago and replaced all the rotors and the pads with ceramics. Then replaced the master cylinder and bleed them twice. They still went almost too the floor. They stopped fine, just really spongy and a long travel on the pedal. This seems to be the fix for me.

[sparkyboy]

Good tip! Keep rollin now that you are comfortable with the brakes!

[CNY_Dave]

Just make sure they aren't spongy because they are pumped up just a little all the time, if the pedal doesn't travel back far enough to uncover the piston passage in the master cyl the brakes will drag when they warm up.

 

Spongy could be unwanted mechanical motion (something flexing or moving).

[Fairtax4me]

You've done one of two things, neither of which actually fixed your problem.

1: you've simply raised the height of the pedal, doesn't change anything in how the brakes work other than now you have to push the pedal farther.

2: you've adjusted the pushrod so the piston in the MC is now blocking the vent ports which allow fluid to exit the MC back into the reservoir.

When brake fluid gets hot it expands, so the vent ports allow that expanding fluid to push back up into the reservoir. Now if the vent port is blocked, that expanding fluid will instead push the caliper pistons and cause the brakes to drag.

 

Main reasons for a spongy pedal are:

air in the lines (which you say you've bled several times, so we'll rule that out)

old or low quality brake fluid,

Seized caliper slide bolts

or a bad wheel bearing causing the rotor on that wheel to push the brake pads apart.

 

Two best things you can do to improve pedal feel are new fluid (valvoline synthetic Dot4 is one of the best and is commonly available), and replacing the brake pads with quality mild performance pads. Not all ceramic pads are created equal, and most parts store ceramic pads are designed for low dust and quiet operation, NOT for better braking.