One problem related to coolant leaking has been reported for the 2009 Lexus RX350. The most recently reported issues are listed below.
My car never leaked oil, and no sensor lights were on. Regular maintenance was performed on the car. While I was driving on the freeway on cruise control about 70 mph (2,000 rpm) engine suddenly revved up to 3,000-3,500 rpm. I was able to exit the highway within 0. 25 miles, the oil pressure sensor came on at the end of the exit ramp. I drove approximately 100 yards away from the exit ramp to reach a side street and by then the car was barely moving, it was very difficult to turn the steering wheel, and several other sensor lights were also on. I had the car towed to a service garage that told me the oil coolant lines had leaked causing the low pressure condition in the engine. After the technician replaced the oil cooler lines and performed an oil and filter change they found "large quantities of metal shavings in oil filter cartridge indicating internal damage of engine. " severe internal engine damage has occurred and engine needs to be replaced. In my experience, it seems that a large quantity of oil was lost very quickly, and if I had not been able to exit the highway within a matter of seconds the car could have seized up and I could have gotten in an accident.