Any of the fan belt driven devices ( water pump, p steering, alternator, air conditioner compressor, etc ) on the front of the engine could shriek if you have a bad bearing or if the fan belt is too loose. The air pump / injection pump only runs when the engine is cold. It gets a signal when the engine warms up to dis-engage its' clutch. So, check the fan belt tension.

__________________
Resistance is Futile.