The HydroVAC works on engine/manifold vacuum, theoretically the brake fluid if leaking internally might be sucked up and ingested by the engine.. Again not sure if that's actually going to happen, worth looking into though. Check your service manual for a cutaway picture of a hydrovac.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0530.htm

Look here too
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0536.htm


Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-