Weird hydroboost issue

[Asterios Anagnostou]

Hey all,

So I have a really specific issue with my HB. Just to preface, my 96 sierra k1500 used to have a vacuum power assist. I purchased a HB from a junkyard out of an 03 Suburban, rebuilt it (orings and seals) and installed it onto my truck with all new lines.

I went through the process of bleeding the power steering. I had to use an old school MC so that I wouldn't have to change the brake line fittings. It's one of the those all iron ones. All I had to do was switch front and back lines on the MC to get it to work. Also, I had to space the MC about 1/16 of an inch away from the HB so that the pushrod wouldn't always be depressing the MC piston.

Ok so here's the issue, when I apply the brakes, it stops on a dime. Feels great. But when I let go, it stays engaged for a second or two, then disengaes slowly on its own and returns fully back. There's always a delay though. I let go of the pedal and it's like, "deh maybe I should let go? OK I'll let go". I have tried to return it faster manually with the top of my foot, but it actually resists me. It insists on returning at its own pace.

Anyone have any ideas as to why this might happen?

Thanks so much for any and all ideas!