I have looked into this problem a great deal (here) ..... it is my opinion that this problem all starts because of the small, delicate solenoid screen in the power steering rack. This little filter is REALLY small and delicate .... when it gets so dirty that it becomes clogged, the entire power-steering system develops far more internal pressure than it should .... leaks develop .... power steering pumps can be affected ..... and so on. Until that little solenoid filter is serviced, the problem is not dealt with at its root.
My car started leaking like this also about the time I first bought it (it had 101,000 miles on it) ..... but I found all this info here and cleaned the solenoid filter first, before I started messing around with everything else. Turned out that my solenoid filter was VERY clogged and dirty ... in fact, the whole system was really quite a mess. After we had cleaned the solenoid filter and flushed the system, all the other power steering system leaks suddenly stopped. My power steering lines were sweating ... that stopped. My steering rack boots were sweating fluid ... and that stopped. My power steering pump had not started leaking or making noise yet, however. I am sure my car has the original power steering pump and it now has 127,000 miles on it. Works perfectly. I am not so sure it would still be working this well today, had I not become aware of the power steering solenoid filter situation .... and serviced it.
Anyways .... my independent mechanic had never heard of this problem until I told him about what I had learned here at the "club" .... but now he knows about it .... and consequently this is now the first thing he checks when anyone else brings in a LS 400 like ours to his shop that has power steering problems. He told me that virtually ALL the LS400 cars he has serviced since have ALL had dirty, clogged power steering solenoid filters.
He charged me $110 for remove the filter, clean the filter and flush the system.
Perhaps I should also mention that the best way to flush the system is to remove the solenoid filter ... then reinstall the solenoid body (minus the filter) ... THEN flush the system .... then re-install the [cleaned] filter. Again .... the solenoid filter is DELICATE and must be treated with great care ..... I am lucky enough to have an independent mech. who will take enough time to not brutalize the filter, but rather clean it with a gentle touch.
Thank God for the Lexus Owners Club ... and all the wisdom contained within these pages ...
hope this helps.
Is there a tutorial on the solonoid filter removal any where on this forum?