Brakes - bit of a weird one?

[BEB]

I'm having a bit of 'trouble' with my brakes.

It is an intermittent problem and what is happening is there is some 'freeplay' on the brake pedal. By that I mean that occasionally I can be crawling along in traffic and go to lightly brake and there is no resistance on the pedal. Push a bit harder and it feels normal and applys the brakes. It is as if something is sticking possibly or maybe it is servo related?

It is best described as 'freeplay' and it doesn't do it all the time as sometimes the pedal feels normal. It feels like by pushing the pedal something is not engaging to push the fluid through the pipes. There is no 'pattern' as to when it does it either.

It has been suggested it may be time to replace the master cylinder seals?

Can servo's be rebuilt with new seals, etc.

Sorry to be so vague. I'm hoping you can shed some light on what is probably something very obvious.

[strictlypersonl]

Usually, when there is a soft pedal when you press lightly, there's some contamination in the master cylinder. The dirt keeps the seal from keeping tight against the bore except when there's higher pressure.

Alternately, the free play in the rod between the booster and the master cylinder is inadequate, not allowing the return port to open consistantly when you release the pedal.

(As long as you're sure that you're not getting pad kickback from rotor runout or loose wheel bearings...)

[NeedAntiVenom]

BEB,

I'm assuming you are not losing brake fluid at all.

If you have bled the lines thoroughly look for scoring or a bad seal on the master cylinder piston or bore. The initial area of travel gets the most wear.

If it was a warped rotor causing the caliper pistons to be pushed back excessively you would likely feel a pulsing when you brake.

Could be loose wheel bearings too (try rocking the wheels to feel for free play) that will also cause the caliper pistons to be pushed back excessively but you may not feel it like you do a warped rotor.

[RallySnake]

Beb,

I have a similar problem. I believe that it is heat related. A couple of my steel brake lines cross over the frame near the headers. When I sit in traffic or creep into a checkpoint very slowly, my brake pedal feels spongy and sinks much more than normal. After I get moving and things cool down, it's just fine again. I think the humidity absorbed by the brake fluid may be boiling. This problem gets better after I replace all the brake fluid. I do this every year, or so. I have tried wrapping the lines with heat reflective material and that helps some. One day, I'll get energetic and reroute the lines farther away from the headers. That will require drilling holes through the frame and I'm not excited about that.

Maybe, this is your problem, too?

Paul