I Have a 2001 4 Door Ford Explorer XLT 51,000 miles and im new at driving suv's and ive just noticed that when I make turns to the left even gradual turns I hear like a sort of hydraulic noise then when I straighten out the wheel the noise stops. It happends when I turn right but its not as loud as when I turn left! Can it be the power steering pump is going? I just bought the truck! The fluid is good and at its normal fill level! What could it be?