2008 Denali 6.2 Roaring sound while accelerating

[Bmurray256]

So I have a 2008 Denali and when the HVAC power button is on it roars when accelerating until it hits high gear and goes away. This only happens when HVAC button is on, if it's off it accelerates with no noise at all. Need all the help I can get.

 

[OR VietVet]

Welcome to the forum.

Sounds like your noise is coming from the a/c compressor when it is engaged and accel from idle. Possible failing a/c compressor. The compressor does cycle with different modes, such as defrost. May be from radiator fans that are activated when HVAC is on. Does the sound get louder the faster you go? What is throwing me is the sound stops after hitting high gear, is what you said. Can you duplicate at all when sitting still and have the hood up and accel and listen or you do have to be moving and trans shifting? Need to check drive belt/idler/tensioner too. Others will chime in with other recommendations. Can you do a video of the noise?

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[intheburbs]

It's the cooling fan(s). At high speed they cycle down because you already have enough air moving through the radiators. Accept it, and let the truck do its thing.

ETA: I would check the fins of all the radiators looking for obstructions - leaves, bugs, etc. Also check your fluid. If it's not cooling effieciently, that could also cause excessive fan noise. The only time my 6.0 roars is 1) In the summer, 2) Very hot outside, 3) Usually towing, 4) Running A/C, and 5) Idling/slow speeds for a while.

 

[Bmurray256]

Welcome to the forum.

Sounds like your noise is coming from the a/c compressor when it is engaged and accel from idle. Possible failing a/c compressor. The compressor does cycle with different modes, such as defrost. May be from radiator fans that are activated when HVAC is on. Does the sound get louder the faster you go? What is throwing me is the sound stops after hitting high gear, is what you said. Can you duplicate at all when sitting still and have the hood up and accel and listen or you do have to be moving and trans shifting? Need to check drive belt/idler/tensioner too. Others will chime in with other recommendations. Can you do a video of the noise?

It only does it when driving. It’s the 2nd new compressor on the truck due to this. I’m confuse. I’ll see if I can get a video to upload.

 

[Bmurray256]

It's the cooling fan(s). At high speed they cycle down because you already have enough air moving through the radiators. Accept it, and let the truck do its thing.

ETA: I would check the fins of all the radiators looking for obstructions - leaves, bugs, etc. Also check your fluid. If it's not cooling effieciently, that could also cause excessive fan noise. The only time my 6.0 roars is 1) In the summer, 2) Very hot outside, 3) Usually towing, 4) Running A/C, and 5) Idling/slow speeds for a while.

Cooling fans??? Well shouldn’t they make this noise when I don’t have the hvac system on?

 

[OR VietVet]

It only does it when driving. It’s the 2nd new compressor on the truck due to this. I’m confuse. I’ll see if I can get a video to upload.

Did replacing the compressor fix it the first time?

 

[OR VietVet]

Cooling fans??? Well shouldn’t they make this noise when I don’t have the hvac system on?

They cycle on and off depending on the engine temp but when a/c is on they stay on.

 

[Bmurray256]

Did replacing the compressor fix it the first time?

No. I thought It was a defect to the compressor. I warranty it out and it still made this noise.

 

[Bmurray256]

It's the cooling fan(s). At high speed they cycle down because you already have enough air moving through the radiators. Accept it, and let the truck do its thing.

ETA: I would check the fins of all the radiators looking for obstructions - leaves, bugs, etc. Also check your fluid. If it's not cooling effieciently, that could also cause excessive fan noise. The only time my 6.0 roars is 1) In the summer, 2) Very hot outside, 3) Usually towing, 4) Running A/C, and 5) Idling/slow speeds for a while.

All fluids are full, engine runs at operating temperature as it should.