Belt squeal help

rippyro · March 1, 2018

I have a 2005 Silverado 5.3 lm7 with 135k on the clock.

For the past couple of months I've noticed slight squeal in the mornings upon cold start. It seems to be a little more noticeable on humid days. It's not very severe and goes away after a short time once the engine warms up. I've been trying to diagnose it, with no concrete ideas. The belt looks used but in decent condition. I tried the water test this afternoon (it had already warmed up and stopped squealing by that time) and it didn't return the squeal. Everything SEEMED to be running true with no belt wobble. Turning on and off the AC doesn't affect it at all either. thinking about just replacing the tensioner and belt to see if that fixes it but before I go out and spend a bunch of money I figured I'd get a few opinions online first. Thanks in advance.

Also, I have two belts and two tensioners it appears. Is that correct?

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casey.mikl · March 1, 2018

Yea as far as belts. Your ac compressor has its own independent belt. Do the belts appear to be cracked? I would replace belts and inspect pulleys when the belts are off

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bgbdwlf2500 · March 1, 2018

10 hours ago, rippyro said:

I have a 2005 Silverado 5.3 lm7 with 135k on the clock.

For the past couple of months I've noticed slight squeal in the mornings upon cold start. It seems to be a little more noticeable on humid days. It's not very severe and goes away after a short time once the engine warms up. I've been trying to diagnose it, with no concrete ideas. The belt looks used but in decent condition. I tried the water test this afternoon (it had already warmed up and stopped squealing by that time) and it didn't return the squeal. Everything SEEMED to be running true with no belt wobble. Turning on and off the AC doesn't affect it at all either. thinking about just replacing the tensioner and belt to see if that fixes it but before I go out and spend a bunch of money I figured I'd get a few opinions online first. Thanks in advance.

Also, I have two belts and two tensioners it appears. Is that correct?

Sent from my Pixel 2 XL using Tapatalk

when you cold start it, take a regular bar of soap and hold it on each OUTSIDE EDGE (not the flat parts, just the "corner" ) of the belt just for long enough that the belt makes a full revolution. You have to do each side of both belts. I'm guessing your setup is like mine that you have the 2nd belt way down low so probably should go from under the truck on that one. Its an old school trick that lubes that part of the belt and it will stop it from squeaking if its the issue. if you try to do this, its at your own risk, it was way easier when there was only one serpentine belt. Just use common sense and keep your hand away from the belt

rippyro · March 12, 2018

Just installed the new belts today. The main belt wasn't too bad. That ac belt was tight as hell though. Had my wife old the ratchet while I fed the belt around. It took some talking to to get it to fit. Got both on without any major problems though. It's been warm and dry (I'm in Texas) but should be getting some moist cold air soon. The main belt was actually in pretty good condition but the AC was worn out. All of the pullies and tensioners looked good. Smooth, no sounds, not loose, and clean. Fingers crossed on the squeal.
The pictures are of the old belts.

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bgbdwlf2500 · March 12, 2018

11 hours ago, rippyro said:

Just installed the new belts today. The main belt wasn't too bad. That ac belt was tight as hell though. Had my wife old the ratchet while I fed the belt around. It took some talking to to get it to fit. Got both on without any major problems though. It's been warm and dry (I'm in Texas) but should be getting some moist cold air soon. The main belt was actually in pretty good condition but the AC was worn out. All of the pullies and tensioners looked good. Smooth, no sounds, not loose, and clean. Fingers crossed on the squeal.
The pictures are of the old belts.

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Theyre both worn, I'm sure that was the issue

Justin-PA · April 9, 2018

I’ve got a 2005 2500hd with the same problem. The squeal is from the main belt, not the ac belt. It’s mostly at cold startup. I replaced the tensioner AND idler to no avail. If I put on a new belt the issue goes away for a couple thousand miles then comes back. Ive tried NAPA and Advance Auto belts. This is very frustrating. I’ll try the soap trick and see if it helps. The other pulleys all appear fine and the belt runs true with no wobble.

davester · April 9, 2018

Do the item's the pulley turns also spin nicely (alternator, water pump, PS pump, whatever else)? And oil isn't getting on the pulley (say, a slow leak on the PS pump)?

Justin-PA · April 9, 2018

Alt, water pump, and power steering pump pulleys turn nice and quiet. Hard to check the crank pulley lol. Just weird it goes away with a new belt. Didn’t see any oil leaks but that’s a good thought. I’ll check closely for that. I did try the belt conditioner stuff and that seems to make it worse.

sdeeter19555 · April 9, 2018

Could the pulleys themselves be worn out?

2012 2500hd 6.0l CCSB 4wd

BigBadSierra · April 9, 2018

Replace the tensioner and belts if you have a tensioner.

They are usually not to expensive and fail more than people think.

I've even seen them fly apart then hit the pulleys then the real damage starts.

I tell anyone with high millage cars to just change them.

lawn_star · April 9, 2018

Bad idler pulley maybe?

Supreme Pizza · May 4, 2018

I am really pissed off that I had to deal with squealing belts on 3 rigs. It made me so mad that I wanted to shoot my rig with my pistol. I searched the internet, I replaced parts, I changed belt tension, I filed down pulleys, I punched walls, and none of that worked. However - I'm glad that I can put all of that aggravation to good use, and here it is:

Your belts make noise do to moisture. Anything "wet" on the belt will cause the noise - such as fog, dew, water, wax, belt dressing, chap stick, wd40, motor oil, Windex, FABREEZ, CHOCOLATE, SPIT AND URINE!!!!!! None of those will not solve the noise. I checked.

After much effort, research and RAGE, I found the solution.

All you have to do is shut off the engine, and squirt a little bit of granular material onto both sides of the belt in several spots. Just a couple little puffs of dust is all it takes. You can use graphite, line chalk, stick chalk, spray-can antiperspirant, etc. The powder soaks up the moisture and the noise goes away instantly. One vehicle - I have to re-apply a little powder every 3-4 weeks, the other rig has only needed it once.

If you buy line chalk, match the color to your rig.

Please report back your results.