same problem here... went to mechanic....was told could be dirty at the power steering reservoir.... mine had to clean a few times. but still the sound is still there... albeit less
no worry guy... it like tats, because it not taken care and moreover the steering fluids in locally made it worst... but trust me its OKIE... It happen to all JAPANESE car...
i wish to find out, with our hot weather esp during afternoon, whats your ride water temp and oil temp? both water n oil, for mine, are da same reading, for eg, if my water temp is at 80c den my oil wil b around that...