2006 Gmc Sierra 1500 making a grinding Howling Sound Front of Engine B

[Orrieboss]

1500 5.3 V8 with 126k.- a few days ago i noticed an intense howling/grinding sound coming from the engine bay toward the FRONT of the motor.... It comes and goes regardless if motor is hot or cold and varies in intensity. It is loud enough that I can hear it in truck with windows up when driving down the road.

 

So Far as I can tell the sound isnt dependent on

 

if the ac/heat is on or off

Whether I am turning or not

If the car is at operating temperature or not, however it does seem to do it mainly at operating temp!

 

So FAR i have replaced these parts trying to narrow down the noise

 

Serpentine belt Tensioner

Water Pump

TStat and housing

 

Still noise....

 

Side note: I have noticed a light clunk when stepping on the throttle HARD. That started a few days before mysterious sound.... The thump almost feels like the torque of the motor pushing itself back for a split second... And then when i let off the pedal it makes the sound again...bad pinion???

[Orrieboss]

turns out it was compressor. Took off main drive belt and started it up and that compressor was howling like nothing else!

[MikeInCtown]

Check the A/C clutch. I have an older truck but I had the same thing happen. The noise sounded like it was coming from the alternator or the idler pulley but once I pulled the smaller belt off the A/C, no more noise. Other things it could be would be the PS pump or the idler pulley as those are the only other two you haven't touched. One would think if it was something internal that by now you would have some severe problems.