can't diagnose knock/squeak

[young_gun]

I've got a noise coming from the engine that I can't seem to figure out. I've tried a stethoscope to no avail and can't tell what side it's coming from either.

Any ideas would be much appreciated. Truck has a new alternator and belt tensioner, but the sound was happening before that. Injectors also have relatively low miles on them.

Here is a link to a short video of what I'm talking about:
http://www.youtube.com/watch?v=q8MYRnt610s

[grancito]

Is that the intermitant click sound? Run it with the belt off, not long, it will have no coolant circulation. If the sound stops, check the vacuum pump and the bearing in the AC compressor pulley.

[AtomicAle]

If you are referring to the annoying high pitched squeak, Sounds like the noise mine made when my vacuum pump began to eat itself internally. If you do need to replace yours save yourself the trouble and be sure to order one with the pulley already attached.

[young_gun]

I forgot to mention that the vacuum pump has been removed (plugged the egr and swapped the upper plenum.)

when I get a chance I'll check the other pulleys - makes sense now that I think about it, old belt tensioner was stiff which is why I swapped alternators. had a brainfart.

thanks for starting me off guys