[OrangeCrush1970]

Dont buy anything new until you:

1 Check your brake fluid level (1/4" below top)
2 inspect your brakes / pads / adjust your drums
3 inspect your brake lines for leaks and cracking
4 inspect your vacum line from the brake booster to your manifold for cracks / leaks.
5 bleed your brake system.

These are all things that you need to do b/f you go out buying new parts...plus it's the cheapest way to locate your issue.

I had this same problem last week. We bled the brakes...not the problem. I then changed my vacum line to the brake booster and applied gasket sealer where the check valve (elbow that you spoke of) inserts into the brake booster. I then adjusted my brakes (drums).

Problem solved. Hope this helps!