TDIGREEN1

First thread - second try

My rear main leaked. Replaced. Eventually got worse. Eventually started leaking over alternator and on front of engine. Could not locate leaks.
Replaced valve cover gaskets, seals and PCV. Did not replace any cam seals because they were not leaking.
NO MORE OIL LEAKS.
If your LS400 has ANY oil leak, replace the valve cover gaskets and PVC. Actually - if not done yet just do it.
LONG STORY SHORT: Don't screw around for 7 years wondering why your new rear main crankshaft seal is still leaking.

Legender

You can easily check the torque on the screws as they are readily accessible. They do loose up over time as well as the valve cover gaskets harden with age and temperature strain. They are a known wear item, just like most seals. I even see this on mom's 2001 LS430.

TDIGREEN1

I lied - sorry - just got done changing antifreeze and t-stat. The front oil leak is still there. Might be the PS pump o-ring but I doubt it. No indication this is the front camshaft seal. The oil seems to be coming from behind that plastic piece of a cover above the timing belt tensioner. It is also dripping off the bottom of the alternator. The oil doesn't look or smell like PS fluid. Might do the PS o-ring replacement just to be sure. Man, I wish it was easier to diagnose oil leaks. Rear main definitely leaking less but still weeping.