The Most Common Causes of Poor Brake Pedal Feel1.The bleeder screws on the caliper are not facing up.2. The master cylinder was not bench-bled or was not bled completely.3. A defective rebuilt master cylinder with pitted cylinder bore or defective pressure seals.4. The master cylinder bore size is too small for system requirements.5. Using disc/drum master on a disc/disc system.6. The master cylinder is lower than the calipers or wheel cylinders and not using correct residual valves.7. Lines or components are near a heat source.8. Lines that lope up higher than the master cylinder and then come back down will trap air.9. Not using a residual valve for rear drum brakes.10. Drum brake wheel cylinders are too large.11. Silicon brake fluid has a tendency to trap air and causes seals to swell.12. Rear caliper parking brake/pistons are not set properly with rear disc brake system.13. Rear calipers are not being bled properly (most brake problems with four-wheel disc systems come from rear brakes).14. Improper pedal adjustment with too much free play.15. Old or poor-quality brake hoses.
How To Diagnose a Problem 1. Disconnect the brake lines from the master cylinder while leaving the cylinder on the vehicle.2. Obtain solid plugs for the master cylinder outlets with the correct threads.3. Plug both master cylinder outlets and try the pedal. The master cylinder is bad if the pedal is very spongy or goes to the floor. The master cylinder is fine if you have a good, firm pedal.4. If the master is fine, connect the line to the front portion of the system and try the pedal again. The front part of the system is fine if the pedal remains firm. The problem is with the front half of the system if the pedal goes to the floor.5. Connect the rear portion if the pedal is fine with the front part of the system connected. The problem is in the rear if the pedal goes to the floor.6. It will be easier to fix once you know which portion of the system has the problem.