Did you purge the air from the PS system? That's critical.

When doing some work where it was a good idea to remove the
PS pump, I did the following subsequently to purge the
system, from http://timingbelt.soben.com/ :

With everything back together, and the power steering
reservoir full, take the steering wheel and turn it back and
forth 50 times.  Again, with the power steering reservoir
full, get a friend to standy by with a bottle of power
steering fluid as you start the car.  The pump will suck
down all the liquid in the reservoir into the system.  It is
CRITICAL that the pump not suck air into the system. Start
the car for 1 second and shut it off.  As the level goes
down have your friend add to the reservoir.  Repeat as
needed until the reservoir level is filled appropriately.
When done, replace the reservoir cap, start the car, and
twist the steering wheel and listen for "squeeling".  As
long as none is heard, you're fine.  Again, it's important
to keep air out of the system.