No fluid to the back brakes

Okay. How are you bleeding them? Manual or pressure bleeding?

How long have you bleed them? Is the fluid in the master cylinder dropping at all when pumping them?

I attached the manual bleed procedure. Just review it and see if there is anything that you may be missing even though this is pretty straight forward. Thanks

My problem lies within the master cylinder itself as I've disconnected the front line from the master cylinder and there is no fluid coming out when your press the brake pedal.

It sounds like the master is defective or it is not bled correctly. here is a guide to help you recheck your work:

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

Please run down this guide and report back.

Sorry for the late reply. The new master cylinder was bad. I replaced the master, Bench bled it and am know getting fluid to both the back brakes. My problem now is that it's like stepping on a brick, it does stop the vehicle but slowly.

If you are lacking assistance, this sounds like the brake booster has failed. The booster is what provides the braking assistance so more than likely you have a leak in the diaphragm.

You can either rebuild it or it would be easier to replace it. Here is the procedure to do this: