Hey guys, the junkyard hydroboost I put on my truck a few years ago started leaking so I snagged another hydroboost from the junkyard and rebuilt it following this guys instructions (which were great and very detailed)Hydroboost reseal tutorial (long) - Ford Truck Enthusiasts Forums

It looks nice and pretty and no long leaks but I have a few problems:

1. At low speeds turning my steering wheel causes the brakes to engage slightly.
2. I can't easily turn my wheel at low speed without reving it up a little.
3. I can hear the pump whine when I turn which is not normal for a saginaw so I believe I have air in the system still. I can't seem to bleed it all out. I followed the forums recommendations and did lock to lock 20 times first with the engine off and then running while pumping brakes.

So here's my question, did I rebuilt it incorrectly or is it just air?

I would appreciate any input you guys have for me!

I don't have great progress photos of the rebuild as my hands were covered in ATF for the most part but here are a few:

 

I converted my truck to hydroboost with my saginaw pump. Put a brand new ford hydroboost on it and now have pump whine. I’ve bled it and bled it and it still has tiny bubbles in it and I can’t turn and brake at the same time. Probably just air in yours too

 

Well after lots of reading online, I believe the spool valve is bad so looks like I'll rebuild the original hydro and slap it in... see if she works better.

For anyone interested, the spool valve has no rubber seal but is machined with tight tolerances to fit inside the bore of the unit.