I am experiencing a loud whistle on my RX 300 at initial morning startup. It lasts for 3-4 seconds and then disappears. Since that is the only time it occurs it is impossible to trace. I have checked for loose hoses, etc, and wonder if it could be belt or water pump noise. I have 102K miles and have had all required service done at Lexus but reside 2 1/2 houes from the nearest dealer. Any suggestions?