I have a 95 LS400 and the power steering sometimes stops this does not happen all the time but is becomming more frequent, the pump has been replaced.

 

If you looked in the newbie thread first (first thread) you would have found this, "The power steering bible" https://www.clublexus.com/forums/ls4...ing-bible.html
Read #3 in the first post, it give you the answer and how to fix it. Also will tell ya how to flush the system and just about everything ya need to know about your power steering.