Any ideas

This just started happening. No idea what or where the noise is coming from as it’s only me around. Sounds like a bearing. Only present when hot or long run times. I’m trying to get help to narrow it down

https://youtube.com/shorts/K4YVCmVhUa4?si=g4XBrx0txYDpG9fT

 

Did some further testing. Noise happens with AC on and running but not when off. Sounds like my AC compressor clutch might be failing?

 

@Randomrunner12, Also check the idler/tensioner bearings. When the A/C is engaged, it puts extra strain on those components!

 

Hopefully those aren’t bad as I replaced them 2 months ago with the gates kit from Genos lol. That would suck lol.

 

How so?

 

Are you sure you have the belt routed properly? I’ve seen a belt improperly routed that doesn’t have enough tension on the belt. This allows the belt to slip on the A/C pulley and the belt squeals.

 

Yes routed correctly.

 

Because AC is the last in line of the belt, aside from the tensioner.
But you can see the belt lengthening at the tensioner when the AC kicks in.

(It just happened that I had to change my AC clutch because of a bad bearing)

 

Thanks @Ozymandias for confirming what I was saying!
If you've ever watched when the A/C kicks on, the tensenior jumps from the load placed on the belt! This is also the time that will break a well worn belt!

 

I would agree that more strain would be placed on the idler bearing when the AC compressor engages, but not so with the tensioner bearing.

Any load placed on the belt from any driven accessory will actually put slack in the belt where the tensioner is located, consequently a slightly reduced load on the tensioner. This why the tensioner is the located in slack part of the belt right next the the source of power - the crankshaft pulley.

- John

 

Sorry, but I don’t see increased load on the belt, tensioner, or other accessories except for a split second when the compressor kicks on. Certainly not enough to make a bearing squeal when the compressor is on.

 

Maybe if a bearing is right at the edge to give, then it might be the little more load on it to change from quiet to noise. Aside from that you're right, shouldn't make a difference in a normal setup.

By the way, am I the only one that can't hear anything special in the video?

 

AC compressor is quite a load, takes a couple Kilowatts to run it, not minor.

 

By the way, by playing around with the belt several times in the last 6 months I figured out one thing.
This belt goes super easy in and out once you figured out how. Best vehicle for that job ever owned or worked on, it takes me longer to smoke a cigarette then to change the belt.

 

Ozy, listen closely to the very near end of the video, it sounds almost like a high pitch squeak or squeal. Whatever you want to call it. Definitely wasnt a normal shutdown sound. This truck since I have owned it has always had to typical Cummins belt noise at shutdown but this was very new within last few weeks.

 

Is it always now? At every shut down?

Sure you could take the belt off and spin all the pulleys by hand, not a big deal and it would rule out many spots.

That's what I would do here.

 

Not at every shutdown. Kinda random when it does it now. I’ve been trying to determine if it’s truly related to the AC being on at shutdown. Or not. I have a 45 minute drive to work so since I first posted, I’ve driven home with no AC, no noise at shutdown, drove to work with AC same noise but much shorter length, drove home in morning with AC no noise, drove back to work with no AC and no noise.

I did also start to wonder if maybe because of how much rain we have had here in DFW the last few weeks, wondering if maybe some dirt or mud got into the pulleys and just finally worked itself out?
I’ll pull the belt this weekend and check this pulleys but at this point, letting it ride. Fix it when it breaks.

 

Check the belt and pulleys for oil or other "debris" in the grooves. I had an oil leak that got on the belt and transferred onto the pulleys. It caused the belt to squeak. I'd replace the belt and it would quit for a few days until it got dirty again.