i have a 2005 pontiac grand am and my brake pedal goes to the floor any suggestions on what cause is we bled brakes numerous amounts of times checked for leaks ive replaced master cylinder yes bench it first there no air in lines please someone help me can pump them up holds but as soon let go push again
Here is a test: you can buy 4 locking clamps especially for brake hoses. Clamp all 4 hoses then try the brake pedal. If the pedal still bottoms out, then the problem is not in the 4 wheels.
If the pedal is firm then remove one clamp and try the pedal. Refasten each clamp as you check each wheel. It should isolate the problem area.
If the rears are drums, then another problem can occur. The piston in the wheel cylinder gets sticky and the return springs are weak. Air can be pulled into the wheel cylinder each time you take your foot off the brake pedal. Manual bleeding doesn't help since air keeps being pulled in. The clamps will tell you which wheel.