I own a 2012 Ford F150 Ecoboost 3.5L V6.

So for some reason after my truck has been sitting over night or sometimes even for a few hours, I wont have any brakes at first. I try and push my brake pedal and its extremely stiff or it wont move at all. Once I pump my brakes a few times, my brakes go back to working normally and won't have this issue again unless my truck sits for awhile. Normally has to be over night or at least a good part of the day. Now once the brakes start to function again, those first few pumps i can feel almost like a grinding or something becoming un-seized in a sense. When I did my brake job, (issue was happening before brake job as well) I did notice one of my front passenger pistons was seized a bit but once I pushed on it the piston broke free and it was good to go. I'm thinking it would be that piston but would one piston on a dual piston caliper stop ALL the brakes from working or would it make more sense that its my master brake cylinder under the hood causing the issue? Remember, I have ZERO brakes at first until I pump them a few times. Please help haha


Thanks