Dropping brake pedal hydro boost system

IS IT POSSIBLE THAT THE BELT TENSIONER IS NOT KEEPING ENOUGH PRESSURE ON BELT TO OPERATE POWER STEERING PROPERLY

STOP YELLING.
Almost anything is possible. Can you provide more detail about what is happening and when it happens?

THE BRAKE PEDAL DROPS ABOUT HALF ONLY ON TURN IN REVERSE ONLY, NEW M/C BENCH BLED AND NO AIR IN SYSTEM

Really, please do stop yelling. Turn off the caps lock and you’ll be fine.

Your power steering pump is completely unrelated to your power brakes.

Correction,on Astro’s the P/S pump provides the boost. There have been lots of problems with the actual shaft of the P/S pump shearing off on Astros and Safaris, I don’t think this problem is related to yours though.

Belt tension very well could be the problem. Turn the wheel left or right until it won’t turn any further with the engine running and listen to the belt. It should get very loud. If not, it is likely too loose. Many of the V6 Astros had a small brace attached to the pump and the exhaust manifold. That brace was prone to loosen and/or break, sometimes stressing the front accessory mounting bracket and causing the belt to eventually jump off.