2008 Honda Pilot, started getting a grinding/whining noise two weeks ago; traced it to the power steering pump. The noise only starts up after a few minutes of driving - it makes no noise when the engine is cold. Fluid in the reservoir gets frothy after running for a few minutes. Noise gets louder when turning the steering wheel. I've replaced the power steering pump with a remanufactured one, replaced inlet and outlet o-rings, and I trimmed off the ends of the hose going from the reservoir to the pump inlet because they looked old and corroded. I then reattached the hose with new clamps. I don't see leaks anywhere and I've bled the system twice according to the Haynes manual. The noise has gotten better after all this, but hasn't gone away. What else can I try or look for?
Upon recommendation from a professional mechanic, I used a power steering fluid additive made by Lucas which got the air out and solved the noise problem almost instantly.