I am very nervous about doing that. Considering this engine has 219K miles on it and that I need to get it up to 3,000-4,000 rpm under load to get the noise to start. I have heard that even running them around the block without the belts can pop a gasket or warp a head. Especially with the aluminum components. Back when they were cast iron it was a different story. Maybe I am worrying too much about that...... If you have done it, and others have too, maybe it's not as big a deal as I am imagining....
Is the idler pulley the same as the tension pulley? Sorry for my ignorance.... It looks like the serpentine belt goes around the main engine pulley, the water pump pulley, the tension pulley and the alternator pulley.
Pulley was my first thought. Right before I received the truck ad new water pump and tensioner pulley were put on. When I got it, I fixed the brakes and have been working on this problem since. I took it into a repair shop and they said it was the alternator and they wanted $690 for a new alternator and serpentine belt. I bought a new alternator (AC Delco) and a new serpentine belt for under $300 and changed it out in about 30min or so. I was hoping that was going to fix it, but it was a no go. That is why I came here. I was hoping someone else had gone through this and could help out. The hard part is that I can't get a great sound clip, and even if I could, it is hard to tell where it is coming from. I am going to try and have my buddy stand outside and I am going to drive by him and see if he can get a sound clip that is any clearer. Also, maybe he will be able to identify more closely where it might be coming from. It could be the AC pump..... I tried turning the AC off, but it still makes the sound. That rules out the clutch (I think). It could still be the pulley. I used a stethoscope to try and hear if one of the pulleys was bad, but to be honest, there is a lot of noise in there as it does have high mileage. Also, I am not very well versed in what I should be hearing or not hearing when it comes to that.
Well, I wired the little valve open and took it for a test drive...... No go.... I wish I had some rollers to put the back end on. That way I could put it under load and open the hood to see if I could get a better grip o where the sound is coming from. It's hard to tell while driving down the road. Back to the drawing board. Any other ideas of things to check?
I read some articles about driving in M5 mode and tried that. Same problem though. My next step is to try wiring/clamping the valve open to see if that works. I agree that it is good to eliminate possibilities... It seems like it is something motor/exhaust related as it fluctuates in correlation with stepping on the gas pedal and letting off of it. It's not always at 3,000 rpm, but that seems like the hot spot. As you could hear it slows down immediately after letting off the gas pedal. Picks right back up when I hit it again. Stupid question....., but is "chirp" the right word to describe that sound?
O.K., I was able to make a couple more sound samples yesterday, and this morning. I tried recording them with the windows up and the A/C and radio off to see if I could isolate the noise a bit more. It is a bit clearer. I also kept on it a bit and then let off and pressed again to show how it slows down and speeds up with acceleration. Maybe these sound bites will be better.
Nope, all US units.... My boss does a TON of driving for work, and replaces his truck every 5-7 years, as his mileage is quite high. The body and interior are immaculate. The engine does have a little noise when you first start it up, until the oil gets moving, but nothing very bad. All in all it is a great truck. Better than the old one I drove, 2003 Silverado 1500 LT with 174k miles - still have that one and will pass it on to my youngest son who will start driving in 6 months....lol. I know every mile on that one and it is still nice as well. This one is just nicer inside. I don't complain about any of them, as they are company trucks and I don't have to pay for anything. Quite the deal as far as I am concerned. Since they take care of me, I like to take care of the trucks and don't mind working on them when I need to. Figure that is a fair trade off.
Pardon my ignorance, but if it was lifters, would it make the sound while rev'd up in neutral? It only does it while under load (in drive). I have tried to replicate it while power braking, but it won't do it. There seems to be an engine safety mechanism in place. Also, I will have to read up on AFM, as I do not know what that is, at least not by the acronym.
It starts mostly when getting up to 3,000 to 4,000 rpms and stays pretty constant if I keep it there. If I let off of the gas, it stops instantly. If I step back on, it starts up again. Cruising around town at slower speeds and less rpm's does not start it up. Once I let off of the gas and then ease back on it on the freeway, I can keep it from happening most times. It really is just when it is under heavier acceleration. I hope that makes sense. Alternator was just replaced last weekend, and the water pump and tension pulley were replaced about 3 months ago. Figured we would replace the tension pulley while we were in there.
I have a 2014 Silverado LTZ (very high milage - 219,000) Runs great and still has some power left under the hood. For the most part, it is in great shape. It have a strange noise when acceleration or getting up to about 3 or 4 thousand RPM. It only does it under load, so it is hard to find where the noise is coming from. In the attached video, it takes place at 12-18s and then again at 40-46s. It is hard to hear because of the wind noise, but I can't figure out how to isolate the noise any better. If anyone has any ideas, I would sure appreciate the input. The water pump was just replaced, and so was the alternator, along with the tensioner pulley. I admit my limited knowledge under the hood, but I am willing to learn and fix it, if I can. https://youtu.be/PctCm6Ai09Y
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