This is a 1995 Camry LE with 1MZ-FE engine and about 267000 miles. Other than this rattling noise that occurs at 8 seconds after starting, the car runs great (knock on wood). I cannot figure out where this noise is coming from but have listened with a "tube" to the alternator, AC, starter, timing belt, bearings and cannot detect its origin. It only lasts for about 1-2 seconds and usually only after the car has set for some time (couple hours). I have recently replaced the timing belt, both idler bearings, and the water pump. BUT the noise was there even before all of these parts were replaced, although lasted longer before. Someone has mentioned it might be power steering pump cavitation on start-up, but if I turn the steering wheel to the left and right until lock I can't reproduce the noise. I have checked for loose covers, exhaust, etc. and I am stumped.

Video of starting sound - 8 seconds into the video you can hear it. http://www.youtube.com/watch?v=qjMb4Kw-FTg

 

Sounds like a buzz on the audio.

Might try removing the belts then starting the engine. This would test if the engine or assy were the cause.

Might also look at various vacuum valves, anything powered by vacuum. 8 seconds may give something time enough to draw vacuum then make this noise.

One off the wall suggestion is something like the power brake booster which is vacuum powered.