74 Blazer - Air in rear brake lines???

I have an old 74 Blazer and I'm having problems with air in the rear brakes & brake lines. It's got a fairly new master (6 months) and doesn't appear to have any leaks
anywhere. I've bled, vacuum bled & pressure bled the brakes. The air comes right back after a couple days. Pressure bleeding seems to work the best as the air is all the way up to the master (bubbles when you push the pedal). Has a good pedal after bleeding but slowly goes away. Is it time for another master? Any suggestions?
Thanks in advance.. B-C3
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Hi,     I had the same problem with my 77. My brakes still act funny. The only 2 things I can think of is the front reservoir of your master cylinder sucking air when the brakes are let off. This is possible, but not probable.. Have you checked your rear wheel cylinders for leaks? This is probably your problem. You may be able to see fluid on your brake backing plate. They are relatively inexpensive, but easy to replace. I would check this first. Good luck to you. Jessie
AirCompressorGuy wrote:

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