Hi, I have an 08 Ridgeline that has a low brake pedal (almost to the floor) while driving on first application of pedal and when released and reapplied has a firm pedal. There was no fluid loss and all 4 wheels have lots of brake pad left. I thought possibly brake master cylinder, so I replaced the master cylinder and bled the brake system 6 times until no air was seen at all calipers. With engine off the brake pedal is firm and hold pressure, but when the engine is running the pedal is almost at the floor and the rear brakes only apply lightly. I am wondering if the ABS unit might have anything to do with this issue. There is no ABS light on and ABS still works with the low pedal.

 

I figured the problem out, I found air trapped in ABS unit and a bit of air right at the master cylinder lines.

 

Is there a special procedure to bleed those areas or to activate the ABS while bleeding?

 

I just bled the brakes normally having someone pump the pedal and hold pressure, then I proceeded to loosen one line at the ABS unit to release the air, tighten the line repeat the procedure and go to the next line until I all 4 lines had no air. I also loosened the lines at the brake master cylinder while under pressure which released some air and then proceeded to bleed all 4 calipers in sequence. LF,RF,RR,LR.