steering box/pump trouble

[1963chev]

Hi, I bought and installed an aftermarket quick ratio steering box from CPP and hooked it up to the existing steering pump on my 350 cu in engine. I primed it good but the front of the steering box blew off while I was backing into the garage within 2 days. CPP covered it under warrenty and I installed the second steering box but I was nervous so I bought a rebuilt power steering pump. As I disconnected the old pump a small amount of rusty brown tranny fluid came out of the low pressure line before it flowed the nice clean red fluid that I had put in during both installs. Now this old pump had been completely drained and I used new fluid on both the box that blew up and on the second install. I had good pressure because you could turn the steering wheel with one finger. Doesnt the fluid circulate? How could I get dark rusty brown fluid in one spot right after shutting the engine off? Any help/ideas out there? thanks