I have replaced the brake master cylinder and bled the brakes. I still have spongy feel to them and it also feels as if the push rod is off, but it isn't at least not at the master cylinder.

have had this on different models and makes and what i do is to push brake pedal down and jam it down a length of wood or anything that holds the pedal down a bit not hard down -and leave overnight .if this fails then renew the master cylinder

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.

The brake system was not bled properly, so you still have air in the lines. The air compresses when you press the brake pedal, making it feel spongy. With no air in the system, the brake fluid does not compress, giving a firm feel.

Hello Patricia,

Have you checked the master brake cylinder reservoir for brake fluid loss?

I don't suspect the master cylinder as you have replaced it... but am more suspect of a leaking brake line or fitting which should have
been discovered when you had the system bled.

The only time I ever had a rear brake problem with a 2500 series Chevrolet was due to seized rear brake caliper guide pins...as your calipers are also new that is not your problem.

If your brake pedal feels spongy and travels to the floor board you have air in the system, a brake fluid leak or a failure in the power steering system, such as a broken hose, broken power steering pump drive belt, or failed pump, would result in a loss of pressure to both the hydro-boost and steering.

Find more information here:

. Hydro Boost Power Assist Systems Operation Diagnosis and Repair

if you can see brake fluid around the booster then yes it is most definitely not right, but sometimes these can fail without any fluid noticable, the visible fluid could mean that the brake master cylinder is failing & this will have an adverse affect on the booster power & performance, check your brake master cylinder first as this is a much simpler & easier repair than the brake booster & can be done at home on a flat drive or or street even, a Haynes manual is invaluable for the home mechanic & i recommend you get one as soon as you can as this will help you diagnose the problems with your vehicle before going to a mechanic/garage, if it is the brake booster at fault then i suggest you go to your local scrapper/breakers yard armed with tools & the Haynes/Chilton's Manual (Depending on which side of the pond you are from) & remove the brake booster from a now deceased Toyota 4Runner & remove the brake booster & master cylinder in one should only cost you a few Quid or Bucks & replace the part once your vehicle is back at home, once the parts have been replaced the brake system will need to be bled so that there is no air in the brake lines, this can be easily done with two people at home, Jack up one corner, remove that wheel & then just crack off the bleed nipple of the brake line Putting a bit of clear hose over the nipple to catch the excess brake fluid in a jug etc & have a friend push down slowly on the pedal, when only fluid comes out with no air then the system is bled for that wheel, Check the level in the brake master cylinder & repeat the process for the other 3 corners/wheels Once done your brake pedal should fell firm & Not spongy, If you get a spongy feeling when braking after this then there is still air in the brake lines & the system needs to be bled again, of course if you have done it right then your brakes should feel firm underfoot. Please don't forget to rate me, regards, Paul.

Check rear wheel cylinders for leaks. Did you bench bleed the master cylinder?

I would make sure all the air has been bled out of the abs unit and all other components. Any air in the brake system will cause a spongy pedal and is not acceptable.

Master cylinder is toast.

I have a 2001 Chevy 1500 4 X 4 that recently had all new pads, rotors, and calipers installed. Since then my brake pedal goes almost to the floor before I get any brakes. I took it back to the shop and they bled the brakes with no better results. I bled them also with no results. I took the truck back and they installed a master cylinder with no results. It's now at the Chevy dealer and they say it's normal - BS! I had good brakes before I had all of the brake parts replaced, no one can figure it out. If you have a load in the truck or if you tow anything you better be looking at the ditch to avoid an accident. The original brakes would put you nose into the windshield and now I could stop it better the Fred Flinstone way. Anyone have an answer????????

have you check? the master cylinder. sometine when you get the rotors cut they dont come out right because they may be warped or to thin. if you did the job yourself you might have put the calipers in on the wrong side. this happens alot . if your rotors front and rear are fine then switch the calipers to the other side.