One problem related to crankcase (pcv) has been reported for the 1999 Lexus RX300. The most recently reported issues are listed below.
I change motor oil every 5,000 miles, as per manufacturer's schedule. Also performed a 'large' ($1,400) maintenance at Lexus dealer. Car ('99 Rx300 awd) had rear engine seal leak at 68,000 miles. It seems a large number of the Rx300s experience the same problem, due to hardening (defective) seal material abutting a hot crankcase.