Q: I just purchased a new 2013 GMC Sierra 1500 SLE 5.3-liter V-8 with 1786 miles on it, and I'm having the same exact issue you discussed on a previous GMC. There is a high-pitched noise in the cabin, but when the belt is removed, the noise goes away. The dealer has replaced the power steering pump, tried synthetic fluid, a water pump, and radio from another truck. Would the steering rack be the same in my truck as the 2007, or is it something else? The service manager said that the noise was from the throttle body and intake manifold. The dealership had a field engineer drive the truck, and he stated the noise was a normal characteristic of my vehicle. Any insight would be greatly appreciated.
A: The upside to an engineer's visit to a dealership is they're taking your complaint seriously. The downside -- stating the noise is a normal characteristic of the truck -- means GM is not going to take diagnosing your problem any further. That 2007 Technical Service Bulletin dealing with a noise from the steering gear is still an open case, which is not a good sign. Noises described by the manufacturer as a normal characteristic are not a new thing. Most of the time, it means the noise is not a safety-related problem, it's not an extreme noise, and there aren't enough customer complaints to warrant the cost of modifications to correct the problem.
Did they put you in the same truck and prove they all make the same noise? That should verify it's not a failed part, but an engineering characteristic -- good or bad. If the noise is specific to only your truck, they should continue tracking the cause. The fact the noise disappears with removal of the drive belt almost always confirms the cause to be a component driven by the belt, or affected by outputs from the driven components (power steering pressure, refrigerant circulation, alternator output, etc.), or even a vibration transmitting elsewhere. In my experience, any noise from the throttle body or adjoining ductwork should not be affected by removal of the drive belt. Often, it's an intake air leak that can be easily located with a smoke tester. This tool pumps pressurized smoke into the intake system, and the technician sees where the smoke comes out. If they didn't do that, ask to hear the noise in another truck, and ask why an intake noise would be eliminated with removal of the drive belt. It doesn't make sense.
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