This is my first issue where I wanted to reach out for help as I am a really mechanical person. I have a 2004 Chevrolet Avalanche with Hydra Boost brakes. I replaced the brake booster, Master Cylinder, all 4 calipers, all four rotor and brakes. I have did a brake line test no leaks. I have bleed all the brake lines and even bleed the power boost and yet my brake petal goes to the floor when engine is turned over. Any suggestions on what my next step should be. Getting very frustrated right now and you would be my wife’s hero if you could help me fix this issue. Thanks Jimmie

 

My take, did you bench bleed the MC? you still have air in the lines. Double check the line fittings to make sure you have closed all the bleed valves.

 

There s an accumulator on the hydroboost unit, , It may not be doing its job.