This is my first post, unfortunately. It has to be about an issue I’m having with my beloved truck. I have a habit of staying ahead of the curve and solving problems before they occur on my truck because I really like it and want it to last, also, it already has 165,000 on it and it’s an 07.
I recently changed the idler pulley, tensioner (the whole assembly), and put a new belt on it. Ever since I have done that, I have had a chirp. I used the word chip because it’s high pitched it reminds me exactly the noise a cricket makes. This happens especially when it’s cold(er) out, and under acceleration. It also does it while cruising on the freeway and when I take my foot off the accelerator, it at time will continue doing so. When it gets warmer temps out, it continues to do this, just not to the level it does with colder temps.
I’m new to the area where I live, so I don’t really know any mechanics I could ask or pick their brain. Every time I do ask around people, I get a different answer as to what it could be. So I turn to you!
Any help is much appreciated, thank you.
P.S. The truck is just a basic 2007 GMC Sierra 1500 Classic, Work Truck Model, 4.3L V6, Automatic.
The chirp is a indication of a problem, but do not loose sleep over it at this point. You have replaced all the parts for a typical chirp and now you need an adept mechanic to pinpoint the cause with a stethoscope. There are too many options but I do not think you are in danger. There is another wheel that I know it is a $49 part, that could be replaced, Drive on and get it fixed, Don’t feel too bad as this problem was a problem in one of my recent posts. 2 new rollers plus a new belt fixed the noise
Pull the belt back off and spin each pulley to look for any sign of wobble. (Obviously you can’t do this with the crank pulley though). Wrap something around each pulley (like the belt or maybe the old belt), get some pressure on each pulley and rotate it back and forth. Take a straight-edge or use any similar method to carefully look at the pulley alignments.
See what you can find out in terms of anything being out of order.
I will mention that I had a go 'round with a GM vehicle (it was a 3.4L engine in a van though) that was like this. Drove me nuts looking for it. (I too had replaced idler, tensioner and belt). It turned out to be a combination of 2 things each slightly off and working together. One was an A/C pulley bearing that was at the very early stages of failure. In fact, to just spin it, it seemed perfect, but I could get it to chirp a little by putting some pressure on it. But the second part was the crank pulley/harmonic balancer starting to separate - this left the crank pulley off alignment by a very hard-to-notice amount. Anyway - neither was easy to detect nor severe (yet), but when you put the two together under engine power - crickets. So I guess I’m just saying inspect carefully and look for anything that isn’t quite right.
The rubber belts used for the accessories in cars behave in a somewhat surprising way. They contract – rather than expand as most things do – with increasing temperature. That could explain why this chirping is heard more when it is colder. The belt is longer when it is cold, so it doesn’t snug up to the pulleys as much as when it is warm. Have you tried simply tightening the belt a tad?
George, with respect, belts do not contract as they rise in temperature. They expand.
What does happen is that as belt speed increases it tries to form a circle and the lateral load it places on the pulleys increases. Perhaps that’s what you were thinking of?
One thing I’ve seen that can be critical to quiet operation is pulley alignment. Cig suggested checking this, as well as checking for a loose/worn pulley, perhaps and idler pulley. He’s made some good suggestions there.
The 4.3 in my 2000 Blazer was fussy about the which brand of belt was installed. The quietest belt was the Goodyear Poly-V. I once replaced a 3 year old Goodyear with an Advance Auto (Dayco?) belt and the Goodyear belt was quieter than the new one. From then on I stuck with the Goodyear.
I would suggest removing the belt and examining it closely for nick, splits, etc and spinning each pulley and if all is well re-install the belt carefully lining up all the grooves. If the noise returns after all that it might be that a different brand belt is the only solution.
Hi everyone, thanks for the all the helpful reply’s. I will give all this a try today, I’ll start by checking all the pulleys, and if it continues I’ll try a new belt. To answer the questions about the parts the belt and the tensioner were Dayco, and the idler pulley is Gates.
TSBike … Not from personal knowledge, but that’s what I heard Ray say, that rubber belts get smaller with increasing temperature, heard on a recent show. The Wikipedia article (link below) on negative thermal expansion seems to support this idea. Whether it applies to the materials used to make auto belts, don’t know. It could be there are two effects, and the centrifugal-force effect you mention is the more important.
“Rubber elasticity shows NTE (Negative Thermal Expansion) at normal temperatures, but the reason for the effect is rather different to that in most other materials. Put simply, as the long polymer chains absorb energy, they adopt a more contorted configuration, reducing the volume of the material.”
Well, don’t know much about the belt increasing topic. I did however, tinker around and took the belt off. Remove the tensioner put it back on, the belt back on and as of now…There is no chirp at all, pure coincidence, not sure? The real test will be in the morning when it does/did the chirping the most…Not sure if belt related, talked to a feller today with an 8.1 Silverado…Same belt brand, same problem. I’m guessing it’s been the belt???
To see if the belt is chirping or it’s a bearing that’s chirping, just spray some liquid on the grooved side of the belt. Then start it up. About any liquid will do, but things like household cleaners are usually the easiest to find. If the belt is the culprit, it will quit chirping. Of course this is only a very temporary “fix”.
George, I believe Ray made the mistake of believing that all polymers as well as composite materials containing polymers behave alike in similar temperature ranges. They don’t. Polymers can be and are engineered to behave in specific way under specific conditions. A classic example is viscosity modifiers added to oil to make it multiviscosity. They’re microscopic polymer coils that uncoil as the oil warms, increasing its viscosity at a higher temperature to one similar to a higher base weight oil. I believe what you’ve found is simply a definition of negative thermal expansion. I do not believe it applies to fan belts.
I will, however, see if I can find a thermal expansion chart specifically addressing automotive drive belts. I just tried, but was unsuccessful. I’ll try again tomorrow.
Poymer engineering is a complex science. I’m not a polymer engineer, but I know that inferring a simple statement to apply in a broadbased manner can leave erroneous conclusion. I think that’s what happened to Ray.