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2016 Colorado LT+ Diesel 4x4
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Discussion Starter · #1 ·
At first I thought a chicken or small animal got caught under my hood and got more upset when I pressed the accelerator.

My friend listened to it and suggested I replace the idler pulleys and belt tensioner. At 122k miles, that made sense, and I replaced them - found one bad pulley.

But the noise remains. Drives normally, but I got a long trip planned. Any ideas ?
 

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Did you also happen to replace the serpentine belt when you replaced the pulleys and tensioner? If not, that's next and with 122k miles it's close to the interval.
 

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Discussion Starter · #3 ·
Yes, new belt installed with pulleys.

A google
search suggested noise could be from turbocharger: bearings, bent fin, or cracked intake boot ? No codes or engine light showing.
 

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Yes, new belt installed with pulleys.

A google
search suggested noise could be from turbocharger: bearings, bent fin, or cracked intake boot ? No codes or engine light showing.
Bent turbo fins are related to boost and not directly related to RPM, especially if there's no load on the engine and the noise is happening simply based on RPM changes.

If the noise happens when you gradually raise the RPM then it's likely mechanical. Could be the alternator, water pump, timing belt tensioner, etc.
If the noise only happens when you get on the throttle and either rev the engine or accelerate then it could be a boost leak, bent fin, etc.

Another trick you can try to see if it's still something related to the serpentine belt is lightly spray the belt with water with the engine running and see if the noise changes at all.

Does the noise happen at idle? If there are conditions that it doesn't happen or ways you can make it happen then that would be helpful. A video of the noise would also be helpful.
 

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Discussion Starter · #5 ·
After 700 miles we are nearing destination on day 2 of a 2700 mile trip pulling a 6000# ultra-light travel trailer. The sound is getting louder and now is clearly from between the engine and the passenger front wheel. Mpg keeps dropping, now averaging 11.

I'm suspecting that when a chevy dealer worked on it a couple months ago to fix emissions issues caused by bad DEF that some bolts weren't tightened and I now have an increasing exhaust leak, or maybe turbo boost leak. Any thoughts ?
 

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After 700 miles we are nearing destination on day 2 of a 2700 mile trip pulling a 6000# ultra-light travel trailer. The sound is getting louder and now is clearly from between the engine and the passenger front wheel. Mpg keeps dropping, now averaging 11.

I'm suspecting that when a chevy dealer worked on it a couple months ago to fix emissions issues caused by bad DEF that some bolts weren't tightened and I now have an increasing exhaust leak, or maybe turbo boost leak. Any thoughts ?
Is it a chirping like a VW Bug exhaust? If so, you likely have loose exhaust manifold nuts. I dealt with this over the summer while camping in Colorado.

For me it was the nuts for the front/#1 cylinder and I could see soot collecting on the cylinder head. I could also see exhaust shoot out if I revved the engine. If that's your problem as well I can't see how it could be related to DPF repairs.

Another potential source of weird noise and screeching could be loose or missing studs on the turbo where the downpipe mounts to the turbo. I also lost 3 of the 4 studs there close to a year ago. I'm only at 87k miles now.
 

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Discussion Starter · #7 ·
I don't recall VW bug noises, but I have some 2-month-old chicks and it sounds like they are all "cheep"ing at the same time.

In RV park for the night, will take a look at bolts and studs in the morning, if possible, or listen carefully.

Immense thanks for sharing your wisdom !!

Got the colorado 2.8 new as an easy to climb into farm truck, that now has canyon denali heated/cooled seats, hd extendable towing mirrors, an ARE cap, and BFG E-rated AT tires. Tows 6000# with only minimal sway issues, even in today's 14mph crosswind on I-10 EB.
 

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At first I thought a chicken or small animal got caught under my hood and got more upset when I pressed the accelerator.

My friend listened to it and suggested I replace the idler pulleys and belt tensioner. At 122k miles, that made sense, and I replaced them - found one bad pulley.

But the noise remains. Drives normally, but I got a long trip planned. Any ideas ?
Hi check replacement all alternator bearings it has 3 of them including the clutch pulley had the same problem I replaced the tensioner and the serpentine belt now it's like new
 

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Sound now gone. Mechanic removed and reinstalled exhaust manifold with new gasket and bolts. 5 hr labor.
Thanks for following up!

I'm not sure how often or where you use your exhaust brake, but if you felt like the EB had become weak lately the exhaust manifold leaks will definitely cause that. I noticed an immediate difference in my EB working much better once I fixed my leak. I had felt like it wasn't working as well while in Colorado this summer but didn't think much of it as this was the first time I was towing a lighter trailer in the mountains and thought maybe it wasn't being as aggressive. Nope. The leak allowed a lot of pressure to escape, I suspect I also had lost some boost and probably caused regens to be happening more often. I just didn't really have any obvious signs of a manifold leak until it started chirping and that's when I found and fixed the issue.
 
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