What is causing the rattle in the component just under the alternator? on 2005 Scion xB

Not too long ago a rattle developed in the engine. I purchased a mechanics stethoscope and I think I have isolated the rattle as coming from the component just under the alternator. I have purchased a Scion xb maintenance manual, but it does not come in until tomorrow. Thanks

Asked by for the 2005 Scion xB
Probably your water pump.
1 more answer
What did your maintenance manual book say about the rattling? Mine does this as well. Do the motor mounts need replacing?