One problem related to engine noise has been reported for the 2004 Toyota Avalon. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Toyota Avalon based on all problems reported for the 2004 Avalon.
Car makes a very, very loud screeching sound when started with a/c or heating on (but more commonly with a/c). The sound will sometimes die down or stop once a/c is turned off, but not always. Puddles can trigger the sound as well. Sound can be heard mainly upon inital startup but can occur after car is in motion.