90LS400Lexus, You want to have that leak looked at right away. If it's leaking from the pump, it may be leaking on your alternator (as it can do), you'll also be doing an alternator job.
One thing to consider is a alternator shield:
http://us.lexusownersclub.com/forums/index...?showtopic=5407
Here are the direct links to the pics mentioned in that thread:
http://us.lexusownersclub.com/gallery/LS/Alt1
http://us.lexusownersclub.com/gallery/LS/Alt2