Hydroboost problem

[jborders]

I recently installed a new hydroboost unit and master cylinder from a 1993 2500 truck onto my 68 2wd. 98 percent of the time it works perfectly but every now and then when you are in a parking lot maneuvering and turning the wheels quite a bit you hit the brakes and pedal goes really soft and to the floor. As soon as u step on them again their fine. Upon investigating the problem I've found just sitting in the garage engine running if you turn the wheel lock to lock then hit the brake pedal it will go the floor every time the first time you push it. The power steering pump sounds fine and operates quietly. This is the first hydroboost system I've ever had so its new to me any advice would be appreciated.

[68c10airstream]

HI JBORDERS, sure sounds like a slipping belt! Belts can slip and not squeal. A trick i learned in auto mechanics schooling in the 70's when belt problems were plentiful was this; take a bright colored crayon and strike a line from the center out to the edge on the face of the pulley, looking like a spoke on a wheel. Have someone maneuver the steering wheel to tax the system while you watch the face of the power steering pulley. When it slows down you can really notice the crayon mark speed change when it's slipping sort of like a strobe light freeze framing images. Where you around in the 70's with strobe lights, cool posters lit up with black lights at parties? Well i'll stop now before my kids read this and change their opinion of me, Ha Ha. Good luck, Brian F.

[Tom Vogel]

What kind of remote reservoir are you running on that system?

[jborders]

The belt seems to be good. I have a 5.3 with f body accessories . So the power steering pump is the factory body one with attached reservoir.

[mgchevyparts]

Were the disc brakes on the car before you installed the hydroboost or did you install new brakes at the same time?

[jborders]

It already had disc up front drums in rear.

[mgchevyparts]

I asked because your problem is similar to calipers hitting the frame on a full lock to lock turn. If a caliper hits, such as on the frame, when the brakes are applied the piston will get knocked in and your pedal goes to the floor, as soon as you pump the pedal the brakes return as the piston moves back outward and refills wih fluid. If this never happened before it's probably related to the hydroboost