TomL

Hello, I have some noise issues and would like to hear from anyone who has had same or have an idea what is going on.


2007, 5.9L, 2500, 2wd. I had a bearing a/c pump noise start about Sept 2015, took it to a shop and they replaced the a/c pump. All good for a few months, then I start having a metallic sound when first start of a/c but cannot repeat the sound for 12 to 24 or more shut down hours. Talked to shop who did work, left the truck 3 days, NOT the comp says them. Ok says I. Told him I also have this same, only much louder metallic noise but it is straight in front of driver. Repair shop points to belt or tensioner. I just changed to new belt, 107,689 miles. This am start up, truck cold, ambient around 53 degrees, after engine warm up engage a/c, there it is again, right in front of me but it will not repeat until 12 plus hours shut down.


Does anyone have an ideas, is it possible I am hearing a sound made by the multi groove serpentine belt, not really metallic as opposed to the V-belt squeal, as in loose or not enough belt tension upon start up, do I need to replace tensioner unit? Thanks for reading, any/all replies greatly appreciated.

Mexstan

Have you tried loosening the belt and spinning the idler pulley, alternator and tensioner pulley's by hand. Feel for any roughness and wobble. All should spin freely and have zero wobble. Also, remove the belt completely off the crankshaft pulley and start the truck to see if there is any noise. While I doubt if it is the P/S pump, spin that as well while the belt is free.

For now going to ignore the fan clutch even tho that is a remote possibility.

TomL

Mexstan, I had to scrape and wire wheel the 3 smooth pulleys, appeared to be caked up with belt material. I am referring to the tensioner, water pump and fan pulleys. I did not turn/spin the grooved pulleys; alt/a-c/ps/idler, and did not roll engine or start with belt off. It's curious the metallic noise started from the a/c side and has now moved to the p/s side and louder. The cleaning of the pulleys and a new belt are the only changes to the motor and its accessories. As mentioned above the a/c shop says no issue with pump/clutch. Thanks

saggonwaggon91

As Mexstan said, take the belt off before the first start of the day and see if the noise is there. I have seen main bearings doo the same thing.

TomL

W91, I can do that but suppose there now is no noise to be heard from the engine compartment and as I mentioned the noise I am hearing only makes itself heard when I turn on the a/c after start up? As in resistance from a/c pump, ps pump and it only happens once upon cold start. After the engine/belt/accessories have warmed it will not do it again. Thanks.