Rear brakes not working

[Fachoo]

brakes dont lock

handbrake might help

 

[BlackVXGTS]

If the brakes lock up with abs, there'd be an ABS module problem.....

There are no HSV changes to the ABS.

 

[BlackVXGTS]

.... I changed the brake booster, master cylinder.....

Did you bench-bleed the master cylinder before installing it in your car? If not, that could be your problem. Very difficult to get rid of any air trapped in the master cylinder otherwise.

 

[Satann]

Did you bench-bleed the master cylinder before installing it in your car? If not, that could be your problem. Very difficult to get rid of any air trapped in the master cylinder otherwise.

Ive never needed to do that before and ive changed many master cylinders in my life

 

[Sabbath']

Time to take it to a proper mechanic.

 

[krusing]

Callipers seized ?

 

[stick3]

you can bench bleed in the car need somebody to pump the pedal and hold than crack the top nut/pipe to let air/ fluid come out and do the same with the front nut/ pipe that goes the rear brakes just have cover the area with plenty of rags and water i have done it i followed markovr instructions he a brake guru on here

here is here detail post 68 page 7

https://forums.justcommodores.com.au/threads/how-to-vt-brake-upgrade.75831/page-7

 

[DavesSV6Tonner]

Sounds like your rear brakes are fine. Chock the front wheels, raise the rear of the vehicle and place on stands, with the engine running so you have vacuum assistance and transmission in neutral have an assistant depress and hold the brake pedal, you should still be able to turn the rear wheels by hand, albeit with some effort.

 

[vc commodore]

Ive never needed to do that before and ive changed many master cylinders in my life

Strange you've never struck any problems before by not bench bleeding the master cylinder....Might be wise to do it as has been mentioned