74 Roadrunner Brake Issues

Car is power brake disk drum, everything is new, brake pedal occationally will not return after applying brakes. When this happens brakes stay applyied until I reach down and manually pull brake pedal up with my foot. Any ideas why this happens? Thanks for any advise!

Pedal linkage to tight or binding?

booster/check valve prob but I would 1st split the booster/mc & check the pushrod clearance to the bottom of the piston recess, want ~1/8", maybe a bit less

unplug the vacuum line to the booster. try again.
if it still stays down then I would check for something binding.
if it doesn't then I would bet on the internal check valve.
had one suck the brakes to the floor while I was driving on the freeway.
gradually pulled them down and I kept applying power till I realized my gas pedal was on the floor and I was barely keeping up with traffic.

Thanks for the input guys! I'll look into those items this weekend and see what I come up with.

Well I know it's been a while since I asked about this brake issue, but I finally got to working on it and here is what I got. Replaced booster, mc, checked all linkage, etc.. After replacing booster pedal doesn't stick down, but now I hardly have any brakes. New mastercylinder went on at the same time which was bench bled and bled brakes at all 4 corners. Problem is as you pump up brakes they intially go to floor then will get hard mostly to top, but after stopping for a few seconds and pumping again they go striaght to floor again. They are actually worse than before with the exception the pedal hasn't stuck down yet. I am thinking I still has air trapped somewhere but no matter how much we bleed them I can't get any air out, in fact I only got air out of the left rear and that was the first crack of the bleeder then no more. Any ideas will be very appreciated! Thanks moparts!

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I am thinking I still has air trapped somewhere, in fact I only got air out of the left rear and that was the first crack of the bleeder then no more.

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I agree "air". If your sure the M/C is bled out I'd work on the 4 corners some more & some prop valves need the pin pulled out (& held out w vice grips) to bleed the fronts