Engine noise. Water pump?

[esse10]

Originally Posted by CrimsonEclipse

2011 Yaris USA
When I first start up, there's a noise that sounds like an old school hydraulic pump power steering pump.
Since the P/S is electric....

The sound occurs stationary and in motion and changes tone with the engine RPM. It also goes away after the engine warms up. It's also a lot more noticeable in cold weather. The sound does not change if the A/C is on or off.

I'm guessing that it's either the water pump or the alternator.

I'm not losing any coolant.

Should I just leave things alone?

I had a very similar noise 2 yrs ago and it wind up being the alternator bearing. especially during cold weather. they're fairly easy to replace you might consider buying a throw-down unit , put it in there . you'll have a spare for when it really goes completely out.