MG Car Repair: Rear Brakes Wont Bleed on 1976 MG Midget, rear brakes, flex line

Question
I have a 1976 MG Midget (US).  My rear brakes will not bleed.

The procedure I am following as per my MG shop manual is to bleed the passenger side front and rear brakes at the same time by opening the respective bleed valves, depressing the brake peddle half way, etc.  The front brake bleeds fine.  The rear brake will not bleed.

No fluid or air comes out the rear bleed nipple.  When closing the front bleed valve and leaving the rear bleed valve open, the brake pedal is firm and will not go down very far -- feels like it should when the system is completely closed.

Any suggestions on how to troubleshoot what is happening?  Am I missing a step or doing something wrong?

Thanks in advance for your help!

Answer
Hi Jas,
First bleed at each line fitting on the master cylinder to confirm that fluid is coming out under pressure from each of the two line fittings. Then do the same at all 5 lines at the PDWA valve to see if it is a valve problem. You only have to loosen a line just a little while pedal pressure is applied to see if fluid is coming out under pressure. It could be a valve problem or possibly a swelled up solid rear flex line or even a pinched hard line between the PDWA valve and the rear flex line. By opening one line at a time under pressure you should be able to find where the lack of pressure is. Check the switch on the PDWA valve to see if it is operating the warning light too.
Howard