Brake Pedal Fades, 95 Aurora

[95Antelope]

Spooky new problem started three days ago. The brake pedal fades after application. Hold it down and it will hit the floor in about 5 seconds. Works good until then, but you can feel it dropping. Drops a little faster under heavy pressure, slower on light (like at a stop sign). Ice storm today shows the ABS seems to be working. Fluid is not low and no visible signs of leakage. front or rear. No ABS warning lights other than normal at start up. Anybody????

[chris_fit]

I had the same problem twice... it's the Master Cylinder. Shouldn't cost more than $200 to fix. Don't know how to do it yourself... i had the shop do it.

[ugsrich]

Definitely the Master Cylinder (MC). It is not brake fade which is a condition that occurs when the temperature of your brakes (rotors/pads) increase to a point wherein the coefficient of friction between the pads & rotors actually decreases. This situation causes a feeling similar to one you may have had with hand-brakes on a bicycle when the rims got wet (you squeeze and squeez but the bike didn't seem to slow.) The reduction in the coefficient of friction reduces the friction force between the pad and rotor at a given pedal force. So, similar to water on your bike's rims, you push and push but the auto doesn't react as you anticipate. Brake fade is a scientific reality and can be verified using empirical data pertinent to the material properties of both the rotor and pads. The likelihood that average drivers' (those of us who are not running NASCAR) will ever experience true brake fade in a modern, reasonably maintained, automobile are extremely low. I would replace the MC as soon as possible.

A short-term remedy while driving is the old-fashioned pumping of the brake pedal. If the pedal does indeed "fall" to the floor, quickly release/reapply and you'll get some addition "pedal" to apply and control your braking. BUT this should not take the place or repair/replacement of the MC or other malfunctioning brake component(s).

[95Antelope]

Thanks guys. I'll swap that this weekend. Yeah - I learned about brake fade the hard way on a Honda 750 with a single front disc and some unexpected traffic. Hardest thing I ever did was let off for a second to cool the disc then hit it again. I'm here, so it obviously worked, but my next bike had slotted and drilled twin front rotors!!!