Toyota Repair: hi pitch whistle when toyota truck running either main bearing or smog pump????, smog pumps, toyota 4x4

Question
Hi Ted,

I just bought a used 1991 toyota 4x4 v6 w/ 161,000 miles, once it gets warmed up and/or I run it for a while, there is a somewhat hi pitched whistle or humm that sounds like it might be either a front main bearing or smog pump  or other ???  How can I best tell what it is and determine how long it may be before it needs fixing.

Thank you much & happy Holidays,
Brian


Answer
Hello, main bearings don't make this type of noise, they don't have smog pumps. First make sure it's not a alternator or water pump noise, the water pump is inside the cover driven by the timing belt, it could also be a timing belt or a tensioner noise, it's hard to say without actually hearing the noise,noises can be pinpointed using a piece of rubber hose with one end to the ear while the engine is running.