I have a 04 C70 LTP. I have noticed that if I ever do aggressive driving the car is responsive but I get this whining or humming noise for the next 20 minutes or so then it goes away. Any ideas on what this could be? There is no noise while driving normally which is most of the time and the Power Steering fluid seems to be at the right level.

 

Inspect your power steering reservoir. Inside is a plastic/brass feed tube that can break off. This will cause air to get in the system and make whining noises for a bit. May be your problem. IIRC it was about 38$ at the dealership, not the lowest price but I wanted it that day.

 

I checked the tube inside and it looks fine however there is Power steering fluid around the reservoir and in might be low. will wait for tomorow and check it cold. My question is do I use ATF or Power steering fluid from an autozone or something. I heard someone say to use synthetic power steering fluid but that was for a 99 mine is an o4 and I am not changing the fluid just adding some. Any suggestions? The manual says to use ATF does not say anything about power steering fluid.