I changed the rear brake calipers on my 2000 chevy Z71 i get oil out of both after bleeding but brake peddle still is spongy

Replace the hoses. One in back for both rear brakes and one on each caliper. They deteriorate on the inside and clog up.

First you want to remove brake fluid from brake resovoir, raise front wheels off ground and set park brake or block rear wheels. Remove front wheels, keep steering wheel unlocked so you can turn rotors side to side. Loosen bolts that hold caliper end gently pry caliper free from rotor, remove caliper and remove pads, use bungy cord to hang caliper away from rotor, have rotors measured to see if they are thick enough to have machined, replace if out of specs. Match up pads with old ones, use anti- squeak red liquid and put layer on back of pads, let dry. Use tool to put pistons back into calipers, slowly put pistons back into bore while opening up bleeder screw so ABS won't be damaged. After rotors resurfaced, wash with rubbing alchohal to remove any oils from hands, install rotors and reverse putting pads back onto caliper and reinstall, torque caliper bolts to factory specs and tighten bleeder screws. Install wheels, torque lug nuts to factory specs and replace brake fluid in resovoir. Lower car carefully to ground and press brake peddle without pumping it. Any air in system should bleed out, if not get someone to help with bleeding system. Road test to ensure no squeaks or pulling, burn brakes in slowly.

Bleed ALL lines at calipers....

There are one of two problems. First your lines or calipers are leaking. Second your power brake booster has a hole in the diaphragm and needs to be replaced. Look on the firewall it will be a round metal container.

For the brake how are the sliding pins on the calipers?They should not be corroded the caliper has to slide on it so make sure they are not corroded.Lubricate the caliper slide pin.If the caliper is clean and clear you are suffering from premature wear and high peddle effort the cause is rear hieght sensing porportioning valve.Make sure the rear height suspension proportioning valve is not affected if you modified the rear suspension you will need a kit . If you did not and the height sensing valve is intact a replacement will be required. As for the High RPM the throttle actuator is at fault

I would bleed the rears too especially if the brake fluid reservoir drained empty. Also you may need to drive the vehicle to seat the brake pads. Check and see how the pedal feels initially before you road test to make sure you don't need to pump the brakes in order to stop. if you do then re bleed all four wheels.If you don't have to pump the pedal and it just feels spongy then try going around the block a few times and see if the pedal stiffens up after the pads have seated.

put a brick on the brake pedal and leave overnight ,see what happens

BY TRUCK HAVING ABS BRAKE.YOU NEED A SCANNER TO BLEED BRAKES THE SCANNER HAS TO RESET OPERATION OF THE BRAKE HYDRALIC SYTEM BEFORE YOU CAN BLEED SYSTEM.

Did you adjust the rear shoes out? If the rear drum brakes are out of adjustment they will give you a lot of pedal travel. If the pads are worn have no fear of that U-CLIP brake spring, just change one shoe at a time. Take the spring off one side, change the shoe, put the spring back on the post and do the same to the other shoe, no problem.

I just went to Brake Masters this morning and had them replace the Master Cylinder since I was experiencing the pedal very spongy and going to the floor. When they replaced the Master Cylinder and they gave me back the car, the brakes were still spongy and going to the floor. I addressed this to them and they took another look at it, but when I took it for a second time, the brakes were extremely spongy. It was almost like they gave me back my car in worst condition to when I brought it in. Can you help?