[2001 Avalon XL has high-pitched, low level whistle]

A visit yesterday with the local Toyota "Field Technical Specialist" at the dealership appears to have finally resolved my concern. The field tech was most helpful and efficient, using a stethoscope to immediately isolate my "low-level whistle" to the rectifier bridge in the newly replaced alternator (Toyota P/N 27060-0A050, 100 ampere, 2000-2004 Avalon XL/XLS effectivities). For this specific alternator at this RPM/current output level, noisy diodes are perfectly normal!

[2001 Avalon XL has high-pitched, low level whistle]

Thank you for checking the TSBs for my year/model. My deduction from this forum (32 viewers) is that my concern may not be commonplace among other 2001 Avalon owners. I will let you know if I ever get any further resolution on this. Thanks, again!

[2001 Avalon XL has high-pitched, low level whistle]

Correct. A new timing belt and a new water pump were both installed. The old timing belt (91,000 miles)looked to me like it was still in good shape.

[2001 Avalon XL has high-pitched, low level whistle]

I'm not sure. My local Toyota dealer told me during my last visit that the whistle "went away" after he removed the alternator belt. I suppose that I could remove the alternator belt myself to verify this fact. After getting the car back with a new, dealer-installed alternator, I noticed that the whistle had lessened in amplitude, but was still present at the same low rpm range (approximately 800-1000) rpm. The same dealer also told me that the tensioning device for the timing belt also looked good when he replaced the timing belt (also during my last visit). In test driving another 2001 Avalon last night, I noticed that it also had the same low rpm whistle (but with an appreciably higher amplitude!). I'm almost ready to write this off as a characteristic of the 2001-(?) Avalon engine (my 1998 Camry V6 and 1999 Sienna V6 do not exhibit this low rpm whistle), but I would hate to learn after my extended warranty expires in January 2008 that an engine component really was in an early stage of failure back in 2007.

P.S. I live in Colorado at high atltitude, where the air is pretty thin (11.1 psig at 5280 feet, vs 14.7 psig at sea level). I haven't discounted yet the possibility that the whistle could be eliminated altogether by just driving the car to sea level!

[2001 Avalon XL has high-pitched, low level whistle]

2001 Avalon XL (92,000 miles) has high-pitched, low level whistle from engine compartment that is audible to driver with engine at approximately 600-1000 RPM. Is this inherent to the car's normal operation? Replacement of the alternator and the alternator/ac/ps drive belts did not completely eliminate this whistle.