GMC Repair: Problem with a humming noise in 98 Pontiac Grand Prix, pontiac grand prix, power steering pump

Question
We have humming noise in 98 Grand Prix.When you turn left or right it quits.If you go straight it starts humming.Bought new tires about 2 months ago and that is the only things we have done to the car.Any ideas. Thanks,Lynne  

Answer
If it did NOT hum prior to the new tires, I would suspect that the tire pattern is at fault. Would not be the first time.

however, New tires can add extra stress to the power steering pump, Therefore, While driving down the road and you are NOT hearing any humming and you slightly wiggle the steering wheel from left to riht can you barely detect the humming ?. If you can, The power steering pump is your likely suspect.