clutch-related soft brake pedal
10-19-2013, 01:09 PM
#1
Instructor
Thread Starter
clutch-related soft brake pedal
I'm looking to fix a weird soft brake pedal issue. The pedal is firm at the right depression point, then back the car up 3 feet. The brake pedal is now firm but about 1" farther depression. One pump on the brakes puts them back to firm at the right spot. Now drive forward 3 feet, and the pedal depresses an extra 1" again. One pump, and it is firm again at the right spot. This is highly repeatable.
While sitting still, pumping the clutch pedal has no effect on the brake pedal: it stays firm in the right place. Rev'ing the engine with the clutch in or out has no effect. It seems to require using the clutch under load. The clutch operation feels normal at all times.
I replaced the master cylinder and did a full brake flush [but not clutch slave flush], but this did not fix the problem. Inspection of the the calipers and pistons showed no leaks. No brake fluid leaks anywhere.
Before the problem seems to have appeared, I did replace the brake pads with PFC 06, which are 1 mm thicker than stock pads. To install them, I had to back the pistons up 1 mm more than in the past, so maybe that caused something?
While sitting still, pumping the clutch pedal has no effect on the brake pedal: it stays firm in the right place. Rev'ing the engine with the clutch in or out has no effect. It seems to require using the clutch under load. The clutch operation feels normal at all times.
I replaced the master cylinder and did a full brake flush [but not clutch slave flush], but this did not fix the problem. Inspection of the the calipers and pistons showed no leaks. No brake fluid leaks anywhere.
Before the problem seems to have appeared, I did replace the brake pads with PFC 06, which are 1 mm thicker than stock pads. To install them, I had to back the pistons up 1 mm more than in the past, so maybe that caused something?
10-19-2013, 05:51 PM
#2
Instructor
Thread Starter
Ok, found the problem.
Reading lots of threads didn't lead to a solution, but it gave me ideas, particularly in the area of pad knock back. I went out found that simply pushing the car alone with the engine idling would create the brake problem. I then felt all the pads, and the right rear pads were loose. Took the wheel off spun the rotor and it grabbed hard. Then I noticed cracks in the hub. So that is it: cracked hub causing wobble causing pad knock back causing weird brake peddle feel. I'm luck the wheel didn't fall off. Seriously.
Reading lots of threads didn't lead to a solution, but it gave me ideas, particularly in the area of pad knock back. I went out found that simply pushing the car alone with the engine idling would create the brake problem. I then felt all the pads, and the right rear pads were loose. Took the wheel off spun the rotor and it grabbed hard. Then I noticed cracks in the hub. So that is it: cracked hub causing wobble causing pad knock back causing weird brake peddle feel. I'm luck the wheel didn't fall off. Seriously.