AC belt keeps popping off

[j91z28d1]

I fought with a ac belt slinging off on a 08 corvette. never did it for years of hard driving, once day end of the day at the track, it slung the belt and took out the main belt. almost cost me an engine full over heat 280plus. after that I could make it toss the belt any time I wanted to test it.



after going down the rabbit hole of ls ac belt throwing. it's amazingly common any country there's an ls based engine. with no good info on why or how. people blame everything and I did too, I replaced everything twice. on the early c5's gm installed a top idler pully, not just the tensioner, that helped but didn't carry over to newer stuff. I think they moved to the stretch belts on the suv's over this too.



in the end, I mounted a go pro under the car and went for a drive.. after watching it. it's alignment. I have no idea how it gets out of alignment, it's hard mounted to the block, but I loosened the 4 bolts, had some old sbc starter shims, cut up a 0.030 one and put one under each of the rear bolts, I didn't even see the misalignment, even using a laser belt tool firm work but after the video and shim I saw it then staring me in the face after 6 months lol. that aligned the belt and it's never thrown it again. just got back from a track day a few weeks back and alls still good.


if you jump to a 1:10 ish in this video you can see it.

 

[houstontaylor]

Here's another possibility to consider. I replaced an AC compressor belt tensioner with one from Autozone on my 2003 Tahoe (331,000 miles) within the last year since the belt got loose and the tensioning part had seized up. A month later the new one failed, this time by the spring punching through the casting side. I then replaced it with one from a GM dealer. That one started making random whistling noises within 9 months. Since I assumed wrongly that it couldn't be the tensioner gone bad again, I replaced many other engine accessories before homing in on the tensioner again. Doh! When I just recently replaced that one with a Gates belt tensioner that stopped the whistling noise I notice that the GM one and the Gates one were both manufactured in Canada and looked identical (not sure about the Autozone one). So it looks like there is some kind of manufacturing or quality control problem going on with the AC belt tensioner from Canada at least. Hope my new one lasts more than a few months. Don't assume your tensioner is good just because it is new!

 

[Dekindre17]

I believe in like 2010 GM removed the tensioner and went with a stretch fit belt, I did this conversion on my 04 tahoe. Gates PN: K040355SF

 

[OR VietVet]

My 05 has the tensioner and I used the a/c a bunch with hard accel on my recent 5500 mile trip. Thankfully, no problems.

 

[j91z28d1]

I believe in like 2010 GM removed the tensioner and went with a stretch fit belt, I did this conversion on my 04 tahoe. Gates PN: K040355SF

that was going to be my next thing to try, ditch the tensioner and put that belt on. they seem to work well. there's a cheap special tool to install it.

I'd try it if you still have an issue

 

[OR VietVet]

https://www.amazon.com/Drake-Off-Road-Stretch-Installer/dp/B00AC60VEC/ref=sr_1_16?crid=3CV4N1C599OZX&keywords=serpentine+belt+install+tool&qid=1678158090&sprefix=serpentine+belt+install+tool%2Caps%2C149&sr=8-16

 

[gooffeyguy]

I always found it weird that these motors used a seperate belt for the AC. All my other and past vehicles had the AC on the serpentine belt.

That being said, the belt on my 2001 has only been replaced once and that was about 2 years ago at about 230k miles. It has a tensioner pulley. My son said the AC stopped working and when we opened the hood we saw the AC belt was broken and just hanging there. After getting a new belt we realized the tensioner pulley bearing was locked up and wasn't spinning. We picked up a replacement tensioner from Advanced Auto. Might have been a Dorman or Gates part, not sure. Been fine since.

 

[Dekindre17]

that was going to be my next thing to try, ditch the tensioner and put that belt on. they seem to work well. there's a cheap special tool to install it.

I'd try it if you still have an issue

Personally I used zip ties to hold the belt to the crank while I manually turned it over but either way will work.

 

[me88]

I believe in like 2010 GM removed the tensioner and went with a stretch fit belt, I did this conversion on my 04 tahoe. Gates PN: K040355SF

Must have been earlier, my 2009 has the stretch belt without tensioner for the AC.

 

[Geotrash]

I fought with a ac belt slinging off on a 08 corvette. never did it for years of hard driving, once day end of the day at the track, it slung the belt and took out the main belt. almost cost me an engine full over heat 280plus. after that I could make it toss the belt any time I wanted to test it.



after going down the rabbit hole of ls ac belt throwing. it's amazingly common any country there's an ls based engine. with no good info on why or how. people blame everything and I did too, I replaced everything twice. on the early c5's gm installed a top idler pully, not just the tensioner, that helped but didn't carry over to newer stuff. I think they moved to the stretch belts on the suv's over this too.



in the end, I mounted a go pro under the car and went for a drive.. after watching it. it's alignment. I have no idea how it gets out of alignment, it's hard mounted to the block, but I loosened the 4 bolts, had some old sbc starter shims, cut up a 0.030 one and put one under each of the rear bolts, I didn't even see the misalignment, even using a laser belt tool firm work but after the video and shim I saw it then staring me in the face after 6 months lol. that aligned the belt and it's never thrown it again. just got back from a track day a few weeks back and alls still good.


if you jump to a 1:10 ish in this video you can see it.

Wow. Thanks for this helpful insight. Like yours, mine seems to be happening under hard acceleration. What’s strange though is it was fine for 229K, AFAIK so it’s hard to imagine that the mount got tweaked.

Very cool video!