I have a 2001 GMC 2500HD Crew Cab 4wd with the 6.0L engine. Over the last couple of days my steering has been feeling slightly heavy first thing in the morning. I just attributed it to the 15 degree weather but today my wife was driving the truck and the steering got extremely heavy when she was trying to pull into a parking space and then the brakes started to feel a little bit spongy. I checked the truck when I got home and it was a little low on power steering fluid (still on the dipstick) and there were not any leaks that I could see. I topped off the power steering fluid, started the truck and turned the wheel back and forth. The steering wheel would turn about a quarte to a half turn before getting really heavy and feeling like the power steering was not working. Pressing the brake pedal down, it would feel normal when you first started pushing it but if you pressed harder it would go spongy and then firm. If I gave the truck a little gas, say hold it at 1000 rpm, the power steering would feel normal.
Is my power steering pump going out or do I just need to flush it? I doubt it has ever been flushed. Or is there something else that could be causing this?
Also, if it needs a new pump what brands are best to go with? My local NAPA auto parts store has their NAPA Premium line pump with a lifetime warranty in stock, either brand new or remanufactured. I would have to order an AC/Delco, which I believe is the GM OE replacement.