Member, Sport: On DSC: On (>100 posts)
Join Date: Jan 2012
Thanked 8 Times in 7 Posts
My brain cells have been working overtime and keeping me awake at night...
Since my brake pedal goes way down to the floor, it appears to me, that there must be air hiding somewhere in the system. I decided to approach the bleeding process from a different direction that I saw on the internet. I am tired of pushing good, expensive brake fluid through the system and toss it out. What I tried is to run a plastic tube from the bleed nipple up to the MC reservoir and by pumping the brake pedal, push the fluid, and hopefully any air to expel at the reservoir. I raised the front of the up in the air, ran tubes from both front caliper nipples to the reservoir. Had both nipples open some and pumped the pedal with a slow pedal return. I could observe the clear tube and watch till no air bubbles passed by. I must have pumped the pedal seventy five times. Then I raised the rear of the car and did the same separately (left and then right) until no bubbles were seen. I did see some very small bubbles pass by while doing the front calipers and some larger bubbles from the rear. At this point I thought I was near the fix on this. However, upon starting the engine and pressing the pedal, it again went way down.
Later today I remounted the wheels and drove to a secluded place where I could test the DSC and ABS on grass and gravel road. Under hard acceleration and sharp turns the DSC light would light up. Hard braking on the gravel road did engage the ABS where I could feel the pulses. I did notice under the hard braking, when the car was almost stopped, with my foot still hard on the pedal, the pedal would drop lower maybe an inch or so. I repeated this several times with the same pedal drop. Is that normal???
So, yes the pedal seems to go way too far down to the floor.
I wonder if someone could take some measurements of their range of brake pedal travel for me to compare mine to? I used a tape measure with large numbers. With the edge of the tape resting on the top edge of the pedal and the end of the tape at almost right angles to the inclined section of the floorboard behind the pedals. I could lean over to the left and see the measurement to the front surface where the foot touches the pedal. I got measurements with engine off, the point where I could feel the booster is, and under full on foot pressure. Then with the engine running where the pedal ends with full on foot pressure.
After I took the measurements, with the engine off, I was able to push the pedal to the floor (3-1/2"). I let it return and pushed again, this time I measured 4-1/2" (some pump up), and again to 4" (no pump up), one more time all the way down to 3-1/2". Not sure what that means. I will read over the Vehicle Brake Information that xrviz provided and see if something clicks for me.
There is no slop in any of the caliper mounts, the calipers (just rebuilt), braided lines, new pads, new master cylinder. If the booster was bad, it would just make applying pressure harder. With the engine running, I can depress the pedal quite easily. It is when I apply firm, constant pressure, the pedal goes way down.
I don't like losing sleep over this but it is driving me totally nuts!!!!
Long Post but thanks for the input!!!!!