i have a 1990 lexus ls400

go to lexusownersclub.com and check out the discussions there about power steering leaks. You'll probably have to replace the power steering pump and possibly the rack as well.

yeah man, i just had the exact same problem with my 1991 ls400. at first my mechanic thought it was the pump, which was half the problem. the pump cracked. after replacing it, my fluid lever continued to drop. after a week of trip back to the mechanic he finally found that the power steering hose wasnt functioning either. cost about 800 for me to fix. and i have other friends with older lexus also with the same problem.

http://www.clublexus.com/forums/ls400/261358-the-first-gen-power-steering-bible.html

1990 Lexus ls400. Recently purchased vehicle from family member. Vehicle has been maintained. Drove out of my yard, had a low owner steering fluid noise and was hard to straighten steering wheel easily. Drove a couple miles then returned to get my other 14yo vehicle. Instead. Saw a fluid trail down my drive and am hoping it is a cracked line rather than the power steering pump.

I have a 1993 lexus ls400 Dashboard Light not come on in my reverse light not coming on