I thought the stock intake and or exhaust was making noise on my '11. I was talking to a buddy at the local dealership to see if he had ran into this also and he told me about a service bulletin about the middle heater hose at the firewall going to the egr cooler needing to be rotated up. I thought he was crazy until I tried it. The highest part at the bend in the hose needs to be turned to point straight up. I did it a few days ago and my noise is gone! It has to do with the coolant flow and was worse when the truck was cold. Below is the info from GM.
#PIP4826: Vibration Moan Or Buzz Type Noise Heard Or Felt Inside Passenger Compartment
A dealer may encounter a customer concern of a vibration, moan, or buzz type noise heard from either inside the passenger compartment, or from under the hood. Noise may be described as coming from passenger side front of engine compartment, or from cowl area. The noise is heard better when the engine RPM is raised to between 2300 to 2600 RPM.
If the customer concern fits the noise described in this PI, verify if the noise will change if slight pressure is put on the heater hoses. If the noise dissipates with light pressure applied on heater hose, rotating the heater hose may alleviate the noise.
Squeeze the clamp tangs to loosen the clamp on the EGR cooler heater hose (removal of the hose is not necessary so there should be no coolant loss).
Rotate the hose (approximately 60 degrees counter clockwise) on the steel pipe fitting at the EGR cooler. The heater hose has a molded bend and a quick disconnect fitting at the heater core. After the hose is rotated be sure the molded bend is at the highest vertical point or approximately the 12 o'clock position. Rotate or wiggle the hose connection at the vehicle's body side to remove any pre-load in quick-connect at the firewall.
#PIP4826: Vibration Moan Or Buzz Type Noise Heard Or Felt Inside Passenger Compartment
A dealer may encounter a customer concern of a vibration, moan, or buzz type noise heard from either inside the passenger compartment, or from under the hood. Noise may be described as coming from passenger side front of engine compartment, or from cowl area. The noise is heard better when the engine RPM is raised to between 2300 to 2600 RPM.
If the customer concern fits the noise described in this PI, verify if the noise will change if slight pressure is put on the heater hoses. If the noise dissipates with light pressure applied on heater hose, rotating the heater hose may alleviate the noise.
Squeeze the clamp tangs to loosen the clamp on the EGR cooler heater hose (removal of the hose is not necessary so there should be no coolant loss).
Rotate the hose (approximately 60 degrees counter clockwise) on the steel pipe fitting at the EGR cooler. The heater hose has a molded bend and a quick disconnect fitting at the heater core. After the hose is rotated be sure the molded bend is at the highest vertical point or approximately the 12 o'clock position. Rotate or wiggle the hose connection at the vehicle's body side to remove any pre-load in quick-connect at the firewall.
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