One problem related to water pump has been reported for the 2003 Chevrolet Silverado. The most recently reported issues are listed below.
: the contact stated intermittently, when the outside conditions are cold the steering is stiff. This occurs at any speed. The problem is worse when the brake pedal is depressed and turning the steering wheel. The dealership replaced the valve in the power steering. This has not corrected the problem. There is a technical service bulletin, #10013533, regarding this, but no repair available. The water pump gasket was replaced. The transfer case bearings were replaced. Updated 03/22/06.