I just bought a 2008 Sierra and I have been fixing it up. The power steering had a whine at start up, idle, and when turning. I flushed the system with 2 qts of Prestone yellow bottle and the whining has quieted down some and the fluid is amber again (the old fluid was brown). My question is, what can I do to eliminate the noise? I was thinking of running the Prestone for a while and switching to a high grade synthetic like Redline once I save a little money. Thanks for any comments or ideas.