Hi. The pedal will sink to the floor, but only under steady, LIGHT, pressure, a firm push gives a firm pedal and no braking issues. This with the car running (92 Loyale 4wd/5sp/wagon) No fluid loss evident. I changed out the right rear axle bearing last summer and bled the brakes as per the instructions given elsewhere in the site. The sinking pedal remains unchanged. I would rather chase down the problem before it becomes a safety issue, not later. I have gone through this post : http://ultimatesubaru.org/forum/showthread.php?t=39459&highlight=sinking+brake+pedal but the conclusions are kinda inconclusive :-\ and the o.p.'s problem was not quite the same (Pedal sank under firm pressure) Any ideas out there?

Hi. The pedal will sink to the floor, but only under steady, LIGHT, pressure, a firm push gives a firm pedal and no braking issues.

 

I had that happen one time. It never happened again, so unfortunatly, I don't know specifically what it was. Everyting looked & worked fine after that. I drove that car for years after the incident.

This just happened to me it went away after replacing the master cyl. and the rear pistons. Since I did both im not sure which one it was but start with that If no fluid loss is evident at the wheels but you are losing fluid from the res I would suspect the rear . If no fluid is lost at all over time from the res then I think the master cyl. is to blame.

Edited January 2, 200917 yr by Caramanos2000

Your Master Cylinder is worn, time to replace it before a piston cup goes out totally.

Thanks to all - I was pretty sure it was the m/c. Just need to find a warm place to work on it now. :-\

Make sure you bench bleed it before installing.

Thanks, John. Switched my old Dodge cruiser over to DOT5 a couple of years ago, rebuilt the Mopar aluminum m/c, and learned all about bench bleeding a master before installing. Very good point for those of you doing a m/c for the first time.