If you are replaceing the timing belt this would be a good time to service the power steering also.
Since the power steering pump must be loosened any how, remove the reservoir and flush and replace the o ring at the base of the reservoir. This may save you a pump replacement down the line.
This o ring deteriorates and allow air to be sucked in thus causing foaming of the fluid and a noisey pump.

 

Does 2nd gen ('98-'00) LS have timing belts or chains ? Just wondering bcos my '99 is coming up on 80K miles and wondering if I need to prepare for this change.

 

I understand they all have timing belts that should be replaced around 100K.
While its apart also replace the water pump ,idler pulley and serpintine belt.

 

Do you have the O-ring part number for the P/S pump? Is it the same for all LS years? mine is a 99 LS400.

Thanks,

 

I do not have the part number of the O ring but if you take the reservoir to any auto parts store the can match it up or check Lexus parts

 

They all have belts as far as I know. But before just replacing it because it is time, I would inspect it first. Sometimes you can get way more than the recommeded 90K replacement.