What can cause a stiff brake pedal that softens when stopped?

Question

I have a 2002 Toyota Avalon. Overall the car is in excellent shape, no major issues.

Recently, I have noticed the brake pedal requiring increasing pressure, but only when moving (which is obviously when I am using the brakes!)

When I come to a stop, the pedal immediately "softens" and feels less stiff. For instance, if I am going down a hill, I need to apply decent pressure to come to a stop at an intersection at the bottom. As soon as I reach the bottom of the hill, my foot will sink an inch or two down with the pedal.

Stopping distance and such are normal. I do have a little vibration when braking so I know I need to get the rotors machined or replaced, but is this pedal issue related?

Answer 1

It is possible you have a vacum issue that is effecting the brake booster.Check the hose between the booster and the engine for cracks.There is also a check valve mounted in the hose.Do you detect an engine vibration or noise if you pump the brake pedal several times while stopped and in park?With the engine off depress the brake pedal several times until it gets firm.With your foot still on the brake start the engine,does the pedal depress a little more before stopping?If not the problem may be in the booster.

Answer 2

This definitely sounds like a Power Brake Booster issue. If you stop at a light and the pedal slowly floors out then you likely need a New PBB. Check your Booster: Turn on the car and press the brake pedal, hold it for about 15 seconds, if it floors out, chances are you need a new PBB. Also Press on the brake pedal, if you hear a "WHAUGHT" sound (vacuum in reverse) when releasing the pedal then you need a new PBB. Very easy fix. about 1 1/2 hour for the experienced mechanic and 5-7 hours for the inexperienced mechanic.