This is strictly a noise issue. All of the parts of the steering system are working if you never lose power assist.
First check the power steering fluid level and be sure it's full when it's cold. If it's real low, the pump will suck up air.
You should be able to pinpoint the noise with a stethoscope while a helper slowly turns the steering wheel. Auto parts stores sell them for less than ten bucks. Buzzing noises that power steering pumps often cause can travel through mounting brackets, and through hoses. Hoses can be mispositioned and rubbing on the body. That will easily transmit the normal buzzing into the passenger compartment.
If you find the source of the noise to be coming from the rear of the power steering pump on the fitting where the high pressure hose connects, you're hearing the pressure relief valve buzzing. Air in the system will cause that if the system was recently worked on and refilled. It can take hours sometimes for all that air to work its way out. Ford products can take a lot longer and often need special tools and procedures to do what no other manufacturer needs to have done to get the air out.
If the system was not recently worked on and is not low on fluid, the pump could be worn, particularly that pressure relief valve. It's a lot more complicated than a regular pressure relief valve. The cure is a rebuilt pump and give the air time to work its way out, but you might try a different power steering fluid. Dodge had some noise issues in the early '90s with their power steering systems on diesel trucks that idled much slower than gas engines. The noise only occurred in winter. It was solved by using their special "cold weather" power steering fluid. Since they bought their pumps from an independent supplier, it stands to reason the same ones could be used on other car brands and they could develop the same problems. If I'm right, you'll likely find that special power steering fluid at a GM dealer's parts department. If changing the fluid stops the noise, you may very well get away with never replacing the pump.
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Thursday, January 12th, 2012 AT 8:37 AM