First I realize there is already a thread on this topic, Its very old but so am I.I really need some input on this, I have a 94 Toyota 4x4 3.0 vze P/U. VIN classifieds it as a 4Runner Truck. Had since 48 miles now has 250,000. Just about all maintenance has been done by me since the warranty expired, The timing belt and all other belts changed as required. 22,000 mile ago Timing belt, water pump # 1 & 2 Idler pulleys tensioner, everything changed.

No problems ran great. About 500-750 started getting a belt squeaking noise. Only after warm up I ran all the test one could possibly think of still got squeaking. Took all the belts off
and drove truck about 30-40 seconds still got squeaking. Now I'm thinking timing belt area, so I tore it down. Everything looked good tested the # 1& 2 Idler pulleys no wobble or noise upon spinning. The Tensioner also tested good. Replaced the timing belt and water pump, as I had it tore down. ( Didn't see any issues with them either.) Put it back together but I left the upper timing belt cover off so I could at least observe the belt. Didn't see anything at all that was out of wrack. Still got squeaking. Any help or suggestions you might have would be greatly appreciated. From the best of my old ears the noise is indeed coming from under the hood.