AC belt keeps popping off

[Geotrash]

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!

Thanks for this. This is a likely scenario too. The bearing on the original tensioner was still turning without resistance but it had some play in the bearing. It’s possible that the new tensioner I replaced it with isn’t up to the task.

Think I’ll try replacing the belt with a stretch belt. I have the tool for my 2012.

 

[Foggy]

Thanks for this. This is a likely scenario too. The bearing on the original tensioner was still turning without resistance but it had some play in the bearing. It’s possible that the new tensioner I replaced it with isn’t up to the task.

Think I’ll try replacing the belt with a stretch belt. I have the tool for my 2012.

"TOOL" We don't need no stinking tool !!!!!!!!!!!!
ZipTies work better any way.... my tool (gates) I don't even use cause it sucks

 

[j91z28d1]

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!

it'll be interesting if the stretchy belt works. I like the idea of them being simple.


as far as the mounts tweaked, I have no idea and feeling like it couldn't happen is what took me so long to fix the thing. I still don't get it, but besides the obvious failures like worn out parts. from days worth of reading 100 page threads on random forums, it just seems like something happens and when it starts happening, it keeps happening. my guess is something shifts, like old school core shift in Iron cyl heads. I mean there's no adjustment or slop in anything. it should never be not aligned but it sure was.

definitely try the belt thou, I'm curious.

 

[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

I forgot to follow up on this point. I hit the balancer bolt with my impact wrench (low profile) and it was tight.

 

[donjetman]

The harmonic balancer bolt being loose is not the usual problem. The problem is the rubber that holds the outer metal ring to the inner metal hub gets old and deteriorates allowing the outer to move, wobble, and/or fly off.

 

[Geotrash]

The harmonic balancer bolt being loose is not the usual problem. The problem is the rubber that holds the outer metal ring to the inner metal hub gets old and deteriorates allowing the outer to move, wobble, and/or fly off.

Thanks Don. That’s plausible, for sure. If the stretch belt doesn’t at least stop the problem then I’ll replace the balancer.

 

[OR VietVet]

Yep, that rubber buffer gets old and can look ok by the naked eye but under load at speed, can be and act crazy. If this is happening, you typically feel an engine vibration though.

 

[ScottyBoy]

I had a slugging issue with the compressor on my 2001 a little over 10 years ago. At idle, the AC worked perfectly fine. At just over 2500rpms, the compressor started chattering and randomly locking up to where the belt would jump off, and sometimes break the AC belt tensioner. I literally 7 tensioners (yes, SEVEN) before I gave in and replaced the compressor. I replaced the compressor, accumulator, Schrader valves, Orifice tube, and O-rings on every connection I took apart. I replaced the belt tensioner with an AC Delco unit from Rockauto, it has a metal pulley just like the original OEM tensioner. The parts store tensioners with the plastic pulley is the ones that kept breaking.
If you didn't replace the accumulator, it's possible that may be why you are still having slugging. I've always been told that you should ALWAYS replace the orifice tube and accumulator when replacing a compressor, along with flushing the evaporator core and condenser.
But it's also possible that the tensioner could be your issue if it's a cheap tensioner with a plastic pulley. Try a Delco/OEM tensioner first and see if that helps.

 

[Geotrash]

I had a slugging issue with the compressor on my 2001 a little over 10 years ago. At idle, the AC worked perfectly fine. At just over 2500rpms, the compressor started chattering and randomly locking up to where the belt would jump off, and sometimes break the AC belt tensioner. I literally 7 tensioners (yes, SEVEN) before I gave in and replaced the compressor. I replaced the compressor, accumulator, Schrader valves, Orifice tube, and O-rings on every connection I took apart. I replaced the belt tensioner with an AC Delco unit from Rockauto, it has a metal pulley just like the original OEM tensioner. The parts store tensioners with the plastic pulley is the ones that kept breaking.
If you didn't replace the accumulator, it's possible that may be why you are still having slugging. I've always been told that you should ALWAYS replace the orifice tube and accumulator when replacing a compressor, along with flushing the evaporator core and condenser.
But it's also possible that the tensioner could be your issue if it's a cheap tensioner with a plastic pulley. Try a Delco/OEM tensioner first and see if that helps.

Thank you! Very helpful. I may go ahead and have the system drawn down again so I can replace the accumulator and orifice tube. The compressor is new. The tensioner is new OEM.

 

[ScottyBoy]

Thank you! Very helpful. I may go ahead and have the system drawn down again so I can replace the accumulator and orifice tube. The compressor is new. The tensioner is new OEM.

If you are going to go that far, then I would fix the oil issue. Go ahead and unbolt the compressor and pour all the oil into a measuring cup. I forget the required amount, but I'm sure you can find the factory spec on Google. And after you remove the accumulator, do the same thing, pour all the oil into a cup. Then after ALL the oil is out, only pour back in the actual required amount. So let's say you end up pouring out 11 ounces, but specs call for 6 ounces. Just pour 5 ounces back in.
So once you get a new accumulator, and you are SURE you have the correct amount of oil, recharge the system and then hopefully you shouldn't have anymore issues.

 

[BlaineBug]

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!

Maybe it's the crankshaft that has a little forward/back play in it now after 229,000 miles rather than the mount of the AC compressor. I forget what technical term they call that "play" in engine building land.

Edit: "End Play"

 

[Dustin Jackson]

Interested to see how this plays out. After my AFM delete when I started my Tahoe for the first time my AC compressor made a loud bang when it engaged and ever since then I have noticed it is pretty loud when engaging but it never affected anything.

I don't know how long this has been happening but I always wondered if this was because I lost my mark when torqueing the harmonic balancer bolt and didn't get it slug enough on reassembly.

 

[Geotrash]

Interested to see how this plays out. After my AFM delete when I started my Tahoe for the first time my AC compressor made a loud bang when it engaged and ever since then I have noticed it is pretty loud when engaging but it never affected anything.

I don't know how long this has been happening but I always wondered if this was because I lost my mark when torqueing the harmonic balancer bolt and didn't get it slug enough on reassembly.

Yes, I had been having very similar symptoms for the past year or so.

If it helps, the harmonic balancer isn’t keyed on these engines and can be installed in any orientation.

 

[BlaineBug]

Maybe it's the crankshaft that has a little forward/back play in it now after 229,000 miles rather than the mount of the AC compressor. I forget what technical term they call that "play" in engine building land.

Edit: "End Play"

Would it make sense that end play would be much more pronounced when racing as the motor is experiencing more torque than typical for a classy Sunday drive in the countryside?

 

[Geotrash]

Would it make sense that end play would be much more pronounced when racing as the motor is experiencing more torque than typical for a classy Sunday drive in the countryside?

Possibly, but I doubt it. Also, my engine isn’t the original. I believe it was replaced in either late 2013 or early 2014 with a factory new L92 based on the date stampings on the castings by the previous owner. Best guess based on CARFAX entries bracketing that time is that it has around 100K on it.

 

[BlaineBug]

Possibly, but I doubt it. Also, my engine isn’t the original. I believe it was replaced in either late 2013 or early 2014 with a factory new L92 based on the date stampings on the castings by the previous owner. Best guess based on CARFAX entries bracketing that time is that it has around 100K on it.

I was under the impression that your motor had 229,000. Still too few miles for what one would expect for crank endplay but you never know how it was treated before. If it's a replacement I doubt it entirely. Could be a harmonic balancer issue though that would affect all of the pulleys. Who knows. I can't see how your shims would help now if it never had an issue before unless the pulley on the AC is to blame and has shifted.

 

[Geotrash]

I was under the impression that your motor had 229,000. Still too few miles for what one would expect for crank endplay but you never know how it was treated before. If it's a replacement I doubt it entirely. Could be a harmonic balancer issue though that would affect all of the pulleys. Who knows. I can't see how your shims would help now if it never had an issue before unless the pulley on the AC is to blame and has shifted.

The A/C system and body have 229K, and possibly the harmonic balancer, too. Still worth investigating as a possibility. I’ll have it in the garage next week to tear into. Thanks for all of your helpful comments on this thread - I’m grateful.

 

[Geotrash]

Update: I installed the stretch belt this afternoon along with the Deslugger. Checked the harmonic balancer pulley for smoothness while running and it runs true, and when I had the belts off I worked it back and forth looking for play on the rubber ring under the belt grooves and it's solid.

It was chilly here today (mid-40s) so I took it out for 3 test runs with many full-throttle pulls. The compressor engages smoothly and no problems with the belt popping off. Hopefully it's fixed. I have some road trips coming up so we will see.

https://a.co/d/7oyJIfV

 

[donjetman]

Us a marker and draw a line from inside to out on all surfaces of the balancer to see if things are slipping.

 

[Geotrash]

Update. Stretch belt seems to be working great - no more problems with the belt slipping off so far. I let it sit for 3 days in colder temps and fired it up yesterday afternoon to take it to the grocery store. The initial compressor engagement took about half a second and was much less harsh than before adding the deslugger. After that, every time the compressor engaged it did so normally. As far as I can tell, the deslugger only engages on the first compressor engagement, and only after the ignition has been off for at least 30 minutes. That suggests a revised design than what @gooffeyguy described. I can see no downside to it at this point but I will keep an eye on it through the summer and report back.

Also, I used a sliver sharpie to mark the harmonic balancer as Don suggested and there has been no movement between the inner and outer parts.