I've noticed on some four piston cars that it takes two presses of the brake pedal to get it high and firm.

The inital press is not squishy, still pretty hard, but the pedal travel is excessive; pumping the pedal again results in proper pedal feel and travel.

I've noticed this on a few cars, both with untouched OE brake systems and ones with freshly replaced parts (calipers, master cylinder, etc).

The reason I ask is because we're working on one now, and it exhibits the same symptom. This car has all new calipers, rotors, master cyinder. It has been bled thoroughly, driven, and bled again; no air. It's not the adjustment to the pushrod, because on the second application of the pedal everything is fine.

Any ideas what causes this long pedal travel on initial application? Thanks guys...

Shane

 

There might still be some air in there. Here are some ideas that might help:

* Bench-bleed the master cylinder again. You can do this with the cylinder in the car, just plumb the MC ouput back into the reservoir and slowly pump the pedal until all the air is out.

* Use a pressure bleeder to push a lot of fluid through (available from http://www.motiveproducets.com/). If you have some air in the ABS unit, you'll need to use a lot of fluid.

* Retract the pistons (spread the pads) to eliminate one spot for air to hide.

* Tap the flare connections with a light mallet to free any bubbles that might be stuck there.

Also, some pads are more compressible than others. Some different pads might firm the pedal up.

-Max