PS or HYD PB noise

[Titan IV]

I have a noise that is related to engine speed when it is cold out. It happens more when its cold out. At first I thought it was coming from the Power Steering pump since it is related to engine speed, but now I have noticed that it will start when I hit the brakes. I can't tell if its coming from the power steering pump or the hyd power brake booster. Is there a good way to trouble shoot this? I sure don't want to throw parts at it to see if I can fix it. Btw its a 2004 Yukon XL, 5.3l Flex, with the JH2 brake option HYD POWER, DISC/DISC, 7,200 LBS. I have checked the fluid level. Thanks

 

[electro]

AS of yet, I personally have no idea.

Can you be more descriptive even though you have done well so far.

 

[livingez_123]

I would try flushing out your power steering system and putting in new fluid. Cold weather will also make the pump sound noisy.