Strange Sound From Under Hood

[FB2k]

My parents have a 99 RX300 AWD since new, currently it has about 98,000 miles and it has been properly maintained. But something weird occurred three times in the last two weeks... On a cold start (parked outside for approx. 3-4 hour after driven it), a whirling sound comes out from under the hood (it kind of sounded like an electric RC car), the sound speed up and slows down as the car speed up and slow down, but the car runs and shifts smoothly the entire time, no check engine light of any kind. While the car is in the park position, I slowly press down the gas pedal and there is no whirling sound at all. If I continue to drive it with the sound, it goes away after 10-15 minutes of driving.

The Lexus dealership can't make out what that sound is from, and since its not currently doing it, they can't diagnose it. I've attached a YouTube video of the sound recorded on an iPhone, hopefully someone in this forum had a similar experience and can tell me whats wrong with the RX. Thanks so much in advance!

[Filehorse]

Although diagnosing sounds via a poor audio-quality video is difficult at best, that sound closely resembles the sound my 2000 RX300 AWD was making earlier this year and that was finally determined to be the center idler bearing on the timing belt. You need a mechanic's stethoscope to help locate the sound but that's where I'd start. If it's determined to be coming from the timing belt area and you plan to continue ownership of your RX, take the opportunity to replace the timing belt, idlers, water pump and valve cover gaskets since you'll already have removed most of the stuff necessary to perform those tasks and sooner or later, you'll have to do it anyway. Let us know what you find. This sounds like a job for a reliable Independent Lexus shop.