Check the fluid level and check it for air bubbles. If it's hydraulic related and it's only noisy turning to one side, it could be the valve in the rack itself. The pump can get really noisy when there are air bubbles entering the fluid, and anything that causes it to only happen to one particular side is going to be the rack itself. Check the rack for leaks, particularly around the input shaft.
Other sources of noise like squeaks and pops can come from mechanical sources: steering rack bushings, inner and outer tie rod ends, struts, and strut mounts and spring perch bearings if present.