Rear Brakes won't bleed

1993 Cadillac Fleetwood Brougham

The rear brakes won't bleed the front brakes fliuds comes shooting out when bleed they're ok the brake light is on in the dash only a small amount of fluid come out the rear brake cylinders and they are new, the brake gets hard on two press but it won't stay hard the brake pedal still be moving down.

I checked the proportional valve by loosing the two fittings at the bottom of the proportional valve and i had someone pump the brake and i loosen both fittings fluid came out of both fittings i loosen them one by one and every time i loosen them the brakes was pump before i loosen them.

I don't know if it's the master brake cylinder that went bad.

https://i.postimg.cc/8JHdLVfb/IMG-341.jpg (https://postimg.cc/8JHdLVfb)

Are you cycling the ABS/Traction Control valves and modulator while bleeding?

I don't know where they are located and i don't know how it's done if you do know please tell me how it's done.

I think air probably went inside of the master cylinder because i had the cap off when i was changing my front brake pads and the cap was difficult to put back on it wouldn't clip back down.

You need a scanner capable modulating the valves in the abs unit to properly bleed the system, leaving the cap off has nothing to do with it, maybe you let the master run dry while trying to bleed the system.

If this were a Delco ABS VI unit you could simply cycle the ignition to cycle the EBCM, but not with your model (likely the Teves Mk IV for traction control).

If you actually got air in it, you'll need a bi-directional scanner as the Wedge Driver mentioned, and even worse, it will need to be a pre-OBD II scanner like the old Snap On MODIS or older GM Tech I.

The rear portion of the master brake cylinder when i took the cap off had no brake fluid i would assume that portion is for the rear drum brakes but i will be bleeding the master cylinder when i get a chance.

And do have an OBD Scanner it is one and two but when i connect it to the fleetwood it doesn't turn on if i connect it to a OBD 2 car it turns on as soon as i plug it in.

https://i.postimg.cc/t7WJz7QC/IMG-345.jpg (https://postimg.cc/t7WJz7QC)

SocketB...I was working on my friends Audi,turned out the bleed nipples were blocked