AC belt keeps popping off

[Geotrash]

Here’s a good one for y’all. Earlier this winter while we were up skiing at Snowshoe, I noticed that my AC belt on my 2007 had jumped off and was just hanging from the crank pulley. Over the past year, I had noticed some pretty harsh engagements of the AC compressor up to when it threw the belt so I replaced the compressor, the belt, and the tensioner myself after having a shop evacuate the system.

Fast forward to last weekend, and we had driven to Durham, North Carolina, and I just happen to check under the hood as I sometimes do, and noticed that the AC belt had jumped off again, and was hanging around the crank pulley like before.

And the only thing I can think of is that because the compressor is so low, that it’s developed a slug of oil that takes a while to get moving if it’s been sitting for a few days. When I replaced the compressor, I followed the procedures of the compressor manufacturer, and it was one that came with the PAO oil pre-filled in the correct amount, so I didn’t add any more. I charged up the system, and it was running perfectly.

Then, I noticed that I had a leak in one of my Schrader valves, so I took it to a local shop and had them evacuate the system properly and replace the valve, then recharge the system. However, when I picked it up, the shop owner told me that they added the appropriate amount of oil to the system. I didn’t go ballistic because I should’ve been clearer in my instructions when I dropped it off, but whatever.

Anyway, I’m wondering if I still have a slug of oil in the system that’s causing the compressor to momentarily hang on engagement sometimes. Anyone else run into this?

I see that there’s a company who sells a little gadget called the deslugger, designed to ease the clutch engagement on the compressor. I ordered one, and plan to install it to see if it will help.

Edit: after more reading, it's possible that my accumulator is going bad. Dammit.

 

[pwtr02ss]

I had a Camaro a long time ago that would do that. Turned out to be the harmonic balancer walking out. I replaced the bolt and never had another issue. I doubt that's your problem but its worth a look

 

[gooffeyguy]

Here’s a good one for y’all. Earlier this winter while we were up skiing at Snowshoe, I noticed that my AC belt on my 2007 had jumped off and was just hanging from the crank pulley. Over the past year, I had noticed some pretty harsh engagements of the AC compressor so I replaced the compressor, the belt, and the tensioner myself after having a shop evacuate the system.

Fast forward to last weekend, and we had driven to Durham, North Carolina, and I just happen to check under the hood as I sometimes do, and noticed that the AC belt had jumped off again, and was hanging around the crank pulley like before.

And the only thing I can think of is that because the compressor is so low, that it’s developed a slug of oil that takes a while to get moving if it’s been sitting for a few days. When I replaced the compressor, I followed the procedures of the compressor manufacturer, and it was one that came with the PAO oil pre-filled in the correct amount, so I didn’t add any more. I charged up the system, and it was running perfectly.

Then, I noticed that I had a leak in one of my Schrader valves, so I took it to a local shop and had them evacuate the system properly and replace the valve, then recharge the system. However, when I picked it up, the shop owner told me that they added the appropriate amount of oil to the system. I didn’t go ballistic because I should’ve been clearer in my instructions when I dropped it off, but whatever.

Anyway, I’m wondering if I still have a slug of oil in the system that’s causing the compressor to momentarily hang on engagement sometimes. Anyone else run into this?

I see that there’s a company who sells a little gadget called the deslugger, designed to ease the clutch engagement on the compressor. I ordered one, and plan to install it to see if it will help.

Edit: after more reading, it's possible that my accumulator is going bad. Dammit.

I installed a deslugger about 4 years ago and removed it 3 years ago. Currently sitting in the parts bin in the garage.

I think it's beneficial on a new compressor, but on my not new compressor it just seemed to be a bit annoying and probably not helping any

 

[donjetman]

@Geotrash said: Anyway, I’m wondering if I still have a slug of oil in the system that’s causing the compressor to momentarily hang on engagement sometimes. Anyone else run into this?

Sounds like it to me.
or
The harmonic balancer is slipping on its hub and needs replacement

 

[OR VietVet]

I would be more worried about belt alignment. You said you did compressor and tensioner and the only other place the belt runs is the crank/harmonic balancer. Get in there and check it all out.

 

[Geotrash]

I had a Camaro a long time ago that would do that. Turned out to be the harmonic balancer walking out. I replaced the bolt and never had another issue. I doubt that's your problem but its worth a look

Aight. I agree it's worth a look. I have an extra ARP balancer bolt too from another project.

I installed a deslugger about 4 years ago and removed it 3 years ago. Currently sitting in the parts bin in the garage.

I think it's beneficial on a new compressor, but on my not new compressor it just seemed to be a bit annoying and probably not helping any

Huh. What was annoying about it? Were you having problems like harsh compressor engagement or anything?

@Geotrash said: Anyway, I’m wondering if I still have a slug of oil in the system that’s causing the compressor to momentarily hang on engagement sometimes. Anyone else run into this?

Sounds like it to me.
or
The harmonic balancer is slipping on its hub and needs replacement

Thanks Don. I'll definitely check the balancer bolt and maybe the deslugger will help.

I should also note that both times when it threw the belt *I think* were after hard accelerations to high RPMs. After doing some more reading, it's possible that the accumulator is getting weak and letting too much refrigerant and oil through to the compressor at higher RPMs.

 

[gooffeyguy]

Huh. What was annoying about it? Were you having problems like harsh compressor engagement or anything?

The AC would just seem to cut in/out for the first minute or so after starting. There would be cold air, then not cold air, and it seemed to cycle on/off for a bit.

I know the deslugger is supposed to cycle the compressor on/off very quickly when starting up, but it just seemed to do it longer than I expected.

 

[Geotrash]

The AC would just seem to cut in/out for the first minute or so after starting. There would be cold air, then not cold air, and it seemed to cycle on/off for a bit.

I know the deslugger is supposed to cycle the compressor on/off very quickly when starting up, but it just seemed to do it longer than I expected.

Thanks for that detail. I think I’m gonna install it to see if I can keep it going without damaging it until I can have it evacuated again and do the accumulator and orifice tubes, etc.

My wife is going to be taking a road trip with it next week.

 

[Foggy]

Def look at the alignment and balancer.. I don't think the "deslugger" device
would help your issue at all.. I did a bunch of research on it about 3 years ago,,,
but after my self education I decided against it... It's really just supposed to help
the life/longevity of the compressor... No other real benefits that I could find
I bet your balancer has "slipped" and causing an issue.. Also check the bolts
and the actual mounting of the compressor itself.. if its off even a hair it will throw belts

 

[CorvairGeek]

This may or may not be your issue, but there is a known slugging issue with low mounted compressors, thus the reason for the "deslugger" and the rolled on belt with no tensioner. The description from a former Delco engineer on how and why (and why so infrequent too) was fascinating. I won't even try to give his explanation.
There was a known issue with slugging on high mounted (R4) other GM bodies clear back in the 80s too. No idea why on those. Makes more sense on a low mounted one that ends up full of liquid refrigerant.

 

[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.

 

[me51]

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!