Brake bleeding have trouble with brake bleeding on k 1500 chevy truck, back brakes replaced wheel cylinders and also master cylinder with abs do you do anything different

You have a defective master cylinder.

Ok many people have this problem when they do brakes that ABS equiped. First of all make sure that all your connection are tight at the calipers. Check and make sure you have no visible leaks at all every where on the vehicle. Second alot of people do not know that the vehicle must be running when you bleed the brakes when the vehicle has ABS brakes. So the solution to your problem is very simple check to make sure master cylinder is full, then start your vehicle and have some one pump the brakes then hold down and open bleeder valve. You need to do this several times with ABS brakes,make sure you continue to check master cylinder fluid level continuously. Always start bleeding the brake that is farthest away from master cylinder first then continue to work your way to the closesest. Remeber when bleeding brakes when equiped with ABS the vehicle must be running to allow the ABS pump to run and bleed as well.

well, check the brake lines for leakage after adding brake fluid to the full mark. If the brake pedal goes all the way to the floor, it's likely there is a leak somewhere after the master cylinder. If the pedal gets hard after adding fluid, and pumping it several times with the car off, then the master cylinder is still ok.

If air has gotten into the master cylinder, it may have to be bled out on a bench, or using a scanner if that's the way your vehicle is.

Bleeding the Brake System (ABS) Auto Bleed Procedure NOTE: Perform a manual bleeding procedure. If the brake pedal height and firmness results are not achieved, perform the auto bleed procedure below.
NOTE: Perform this procedure when replacing the brake pressure modulator valve or electro-hydraulic control unit.

1. Perform the manual brake bleeding procedure. Refer to Bleeding the Brake System (non-ABS).
2. Check the master cylinder fluid level often to prevent running the system dry.
3. Press the brake pedal firmly and run the Scan Tool Automated Bleed Procedure (for Gas engines) once, or the Function Test (for Diesel engines) four times. Make sure to release the brake pedal between each test.
4. Perform the manual bleed procedure again. This should remove the remaining air from the brake system.
5. Bleed the system as many times as needed to obtain the appropriate feel of the brake pedal.

sometimes if you leave the bleeder screw open it will gravity bleed the cylinder.Make sure master cyl is full and do one wheel at a time.I have seen this work, I have done it.

To trouble shoot the brake system you have to check:AntiLock Brake System ABS:
Hydraulic Modulator
Basically this unit holds steady or bleeds off pressure in brake line, as necessary, when the Electronic Brake Control Module (EBCM) detects an abnormal deceleration in the speed of the wheel. On 2000 and later models the EBCM and Brake Pressure Modulator Valve (BPMV) are mounted on a bracket attached on the left strut tower.
Wheel Speed Sensors, brake fluid level, brake hoses and lines, inspect and replacement, Brake hydraulic system-bleeding, Brake light switch, check, adjustment and replacement.
Disk brake caliper, disk brake pads, drum brake shoes, master cylinder, master cylinder reservoir, O-rings replacement, parking brake adjustment, parking brake cables inspect and replacement, parking brake shoes-replacement, power brake booster, check or replacement, wheel cylinder inspect and replace.

You bleed it like you would a normal system but you must use the boost assist to do it, in order to do this start the truck pump the brakes three times and bleed that cylinder farthest away from the master cylinder do this twice or until you get clear fluid to run out. add fluid for every cylinder before moving on. Do this for each wheel and after doing all four wheels you should be ready to go. If it feels mushy you will have to bleed it a second time. But you must have the engine running to bleed the brakes unless you have a power bleeder. You may want to bleed the master cylinder first to do this add fluid to the cylinder then pump brakes three times crack the front line open and allow it to bleed air rout of the line do the same for the rear master cylinder once yo get solid fluid from the master cylinder you can dot the same for the ABS then do the wheel cylinders and wheel calipers. This needs to be done sometimes, be sure to never let the master cylinder run out of fluid and check it each time you bleed the wheel cylinders.

One of the wheel cylinders is leaking, pulling air back into brake system and it's going back to the4 master cylinder. Look for brake fluid leaking at one of the wheel cylinders, that's where the problem is.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

start bleding again from left to rigt all the way around.

Hello,
I hope this helps.







Thank You,
Roy

Try a clean and adjust on the rear shoes, because sometimes when they aren't properly adjusted they won't seem to work properly. Also there is a common "squishy" petal feeling after brake work on most all larger GM's around that year, wich I have run into several times. Try test driving it, and put a couple miles on it, That usualy helps.
Good luck!