Brake problem spongy brake pedal pedal goes down replaced front pads and master cylinder and wheel cylinder and bleed lines

If the master cylinder is replaced, care must be taken to prime the new master cylinder by removing all of the air and completely filling it with brake fluid. The spongy feeling is air that is still in the circuits. You will need to bleed the back brakes as well as the front ones again. The order that you bled them seems correct, but perhaps there remained some air in the main trunk lines.

For the best results 2 people are needed. Start at the further distance wheel cylinder and bleed at least three (3) master cylinder reservoir volumes of fluid (back brakes). Bleed the fluid with use of a piece of tubing attached to the bleed port that is long enough to reach almost to the bottom of a long neck or tall clear jar (clear drink bottle works well). When the bleeding begins, after one or two brake pedal pushes, make sure that the end of the tubing is below the surface of the fluid and keep it under. It best to have a clear bleed line (to observe air). Keep pumping the brake pedal while being careful to not completely empty the master cylinder reservoir (leave 1/4 full always). Repeat the same technique for each wheel cylinder with at least two (2) reservoirs full for front brakes. Partially close the bleed ports when almost finished (at least 5 pedal strokes without exit of any air). Completely close the ports during the down stroke of the brake pedal, with the tubing still attached. Be sure each bleed port is closed snuggly.
Most of the brake fluid can be reused, but not the darker portion at the bottom of the jar.

Check the rear wheel cylinders? Was anything leaking at the master cylinder? Does it have ABS?
Check the front caliper slides are free. Check the front caliper pistons for leaks as well. This is all assuming you bled the brakes(all 4 wheels) properly after all that replacement! You're getting air from somewhere for sure or if it has ABS, the pump may have a problem.

it sounds like there is still air in the brake system that has not been removed.you don`t say if you replaced the brake pads and shoes(in which case you shouldn`t need to bleed)or you replaced a brake line(s) or wheel cylinder or caliper.you will have to keep bleeding the brakes all 4 wheels(trucks don`t use bi-directional braking meaning right rear brakes with left front and so on).bleed both rear brakes then bleed both front brakes,was this problem there before you replaced the brakes(soft pedal noticed) and this is why you changed the brakes or the pedal was soft and the brakes needed changing.its possible that the master cylinder has an internal leak and may need replacing.

Is the master cylinder good? a bad master can cause this also did you bleed the master first before bleeding at the wheel and also make sure the bleeder screw is clean, if the hose is good then theres only a few things, a bad master or a master that wasnt bleed, try bleeding the master first then try rebleeding the brakes.

air in system push break down look for bleeder on check valve if not break line loose at check valve retighten . pump break don t fix push pedal loosen another line tighten back check again

You still have air in the system. You will have to bleed more. I had to bleed a quart of brake fluid out of each wheel to get good brakes on my 1996 GMC.

try disconnecting the front line, have someone else then step on the brake pedal and hold it down while you re-install the line. If that doesn't do it, you probably did get a defective master cylinder.

no they are inverted flare fittings no seals check all lines and calipers/wheel cylinders if all are dry remove the vacuum hose from the booster if there is brake fluid in the hose the master cylinder is bad

there is air there somewhere. try manual bleeding the brakes. do the farthest wheel first. if they are calipers all the way around, when you bleed them tap them gently to remove any air that can still be inside the chambers.

robert

it would sound like your master cylinder if you did bleed your brakes right.