mine did that, i added some ATF to the ps and it stoped when it was fully warm and the ps tank was full, i belive my o-ring is out so i will go pick it up today and change the oring, the fluid will thin when cold and the ATF in the tank might be leaking out, all sounds crazy but if i leave the fluid at full it works great.
You may want to try this and see if it is a fix, mine used to be very loud when i first got my car; now there is no click.