I replaced the master cylinder a servo on my mk4 escort yesterday,but now my brakes feel really spongy. Iv bled the brakes but still no joy(made sure rear wheels were on the ground to) I do have a afr gauge fitted and have noticed that when i press the brake pedal the car runs lean, but will return to normal when i lift off the pedal I have double checked everything is tight but im slightly confused now. Anyone shed some light?

cheers

 

possibly an air leak on servo is the running lean bit and i'd take it to a retail park and keep start stop and see if you can push the air to the edges then re bleed again and see if you can raise car by leaving wheels on and putting wood blocks under wheels or use car ramps to make sure valves are open