Diagnosing AC squeal

[Kyngfish]

OK so i was getting a squeal on startup. It would go away when i turned off AC so it's an AC problem.

I replaced all the drive belts and the tension seems fine. I went off to visit the folks for Thanksgiving for 4 days and came back and started her up, and sure enough, squeal - it lasted a little longer than normal, and when it went away, it would occasionally squeal when I revved. In 2 minutes the squeal was gone.

I read through the old threads and they talk about the bearing going out on the idler pulley, or replacing the tensioner pulley.

I looked at the diagrams and the idler and tensioner are the same thing. Right? A new tensioner pulley is like 20 bucks and easy to replace, but how do I diagnose the squeal? When I had the belts off, I turned the tensioner pulley and it seemed to turn smooth. Obviously the problem is occasional and goes away after 30 seconds of running, but it is slowly happening more frequently.

Could it be the compressor? Do I need to worry about any of the pulleys on the crankshaft?

 

[mtbtim]

OK so i was getting a squeal on startup. It would go away when i turned off AC so it's an AC problem.

I replaced all the drive belts and the tension seems fine. I went off to visit the folks for Thanksgiving for 4 days and came back and started her up, and sure enough, squeal - it lasted a little longer than normal, and when it went away, it would occasionally squeal when I revved. In 2 minutes the squeal was gone.

I read through the old threads and they talk about the bearing going out on the idler pulley, or replacing the tensioner pulley.

I looked at the diagrams and the idler and tensioner are the same thing. Right? A new tensioner pulley is like 20 bucks and easy to replace, but how do I diagnose the squeal? Could it be the compressor? Do I need to worry about any of the pulleys on the crankshaft?

If it were a bad bearing pulley, I would think the sound would be constant. So you're saying it never makes the noise when the AC is off?

It makes more sense that a belt(s) aren't properly tensioned. A squealing noise is indicative of a belt that's slipping on the pulley. A properly tensioned belt should have 1/2-3/4" deflection. What that means is when you grab the belt midway between two pulleys and you push down and pull up, it should move down or up 1/2-3/4". If it moves more than that, it's too loose. If it moves less than that, it's too tight. I'd recheck all your belts first and adjust them if they need it.

 

[Kyngfish]

If it were a bad bearing pulley, I would think the sound would be constant. So you're saying it never makes the noise when the AC is off?

It makes more sense that a belt(s) aren't properly tensioned. A squealing noise is indicative of a belt that's slipping on the pulley. A properly tensioned belt should have 1/2-3/4" deflection. What that means is when you grab the belt midway between two pulleys and you push down and pull up, it should move down or up 1/2-3/4". If it moves more than that, it's too loose. If it moves less than that, it's too tight. I'd recheck all your belts first and adjust them if they need it.

Yeah. And to add to that. I smelled burnt rubber when I opened the hood. So the belt is definitely causing the squeak. But that doesn't mean something isn't seizing. I'll tighten it slightly tomorrow and see, but I don't have a lot of deflection and none of the other belts are squealing.

How much pressure should my hand exert to get that deflection in the belt?

 

[JRZEE2000TR4LTD]

Yeah. And to add to that. I smelled burnt rubber when I opened the hood. So the belt is definitely causing the squeak. But that doesn't mean something isn't seizing. I'll tighten it slightly tomorrow and see, but I don't have a lot of deflection and none of the other belts are squealing.

How much pressure should my hand exert to get that deflection in the belt?

One thing you want to check is the idler pulley to make sure it spins freely.

Judging how hard to push to get the 1/4" deflection is tough to describe. The FSM for a used belt (one that's been run longer than 5 min) is 100 +/- 20 LBF. I used a gauge like this to get the feel but only needed it once to get the feel for the proper tension

OTC 4748 Belt Tool - Mechanics Tools


If pulley centers are > 6 inches apart: 1/4" to 1/2" deflection between the pulleys
If pulley centers are < 6 inches apart 1/4" deflection between the pulleys

 

[Kyngfish]

One thing you want to check is the idler pulley to make sure it spins freely.

Judging how hard to push to get the 1/4" deflection is tough to describe. The FSM for a used belt (one that's been run longer than 5 min) is 100 +/- 20 LBF. I used a gauge like this to get the feel but only needed it once to get the feel for the proper tension

OTC 4748 Belt Tool - Mechanics Tools


If pulley centers are > 6 inches apart: 1/4" to 1/2" deflection between the pulleys
If pulley centers are < 6 inches apart 1/4" deflection between the pulleys

When people say idler pulley. Is that the idler on the crankshaft or the tensioner under the compressor?

 

[mtbtim]

Yeah. And to add to that. I smelled burnt rubber when I opened the hood. So the belt is definitely causing the squeak. But that doesn't mean something isn't seizing. I'll tighten it slightly tomorrow and see, but I don't have a lot of deflection and none of the other belts are squealing.

How much pressure should my hand exert to get that deflection in the belt?

Let's do some more diagnosing. With the AC off, turn the engine on. Is there squealing? If the answer is no, turn the engine off. Now turn the AC on and start the engine. Is there squealing? If yes, then it is something to do with the AC compressor. Turn the engine off and find yourself a helper. Again with the AC on (I'd have it on full blast), have someone turn the engine on while you're looking down at the compressor or remove the skid plate and get under the vehicle for a closer look. What's the AC clutch doing? Is it turning like it should be. Is the AC working? i'm just wondering if the compressor is locked up causing the belt to drag on the pulley.

There's two idler pulleys that the timing belt runs on and they are under the timing cover.

 

[mtbtim]

One thing you want to check is the idler pulley to make sure it spins freely.

Judging how hard to push to get the 1/4" deflection is tough to describe. The FSM for a used belt (one that's been run longer than 5 min) is 100 +/- 20 LBF. I used a gauge like this to get the feel but only needed it once to get the feel for the proper tension

OTC 4748 Belt Tool - Mechanics Tools


If pulley centers are > 6 inches apart: 1/4" to 1/2" deflection between the pulleys
If pulley centers are < 6 inches apart 1/4" deflection between the pulleys

I bought this belt tension tool, but it's pricey:

https://www.amazon.com/gp/product/B000I198J0/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

 

[Kyngfish]

Let's do some more diagnosing. With the AC off, turn the engine on. Is there squealing? If the answer is no, turn the engine off. Now turn the AC on and start the engine. Is there squealing? If yes, then it is something to do with the AC compressor. Turn the engine off and find yourself a helper. Again with the AC on (I'd have it on full blast), have someone turn the engine on while you're looking down at the compressor or remove the skid plate and get under the vehicle for a closer look. What's the AC clutch doing? Is it turning like it should be. Is the AC working? i'm just wondering if the compressor is locked up causing the belt to drag on the pulley.

There's two idler pulleys that the timing belt runs on and they are under the timing cover.

Yeah I mean it's definitely the AC. If I turn the car on and it starts squeaking and I turn off the AC then it stops. Turn it back on and squeal. That said it got worse after replacing the belts. So maybe it needs to be tightened. I will try checking the tension and tightening. Then if it keeps squealing I will do as you suggest. It only happens if I start it after sitting all night.

 

[LittleCaesar]

Don't over tighten it. You could kill the bearing in the compressor. The same tool can be had for under $50 on Ebay.

Are the pulleys rusty considering all the salt water around you? I am guessing it is the idler pulley bearing as well.

 

[mtbtim]

Don't over tighten it. You could kill the bearing in the compressor. The same tool can be had for under $50 on Ebay.

Are the pulleys rusty considering all the salt water around you? I am guessing it is the idler pulley bearing as well.

If it's the idler pulley bearing, why does it only make the noise when the AC is on. I'm not a diagnostic genius, but I don't understand your thought process of pointing to the idler pulley as a potential culprit. I would think the sound would be constant if it were a idler pulley. Is it because with the AC compressor on it puts more of a strain on the engine and thus the timing belt causing the idler pulley to act up?

I'm always interested in learning more about our rigs so some explanation of why you and [MENTION=107674]JRZEE2000TR4LTD[/MENTION] think it could be an idler pulley would be much appreciated.

 

[JRZEE2000TR4LTD]

If it's the idler pulley bearing, why does it only make the noise when the AC is on. I'm not a diagnostic genius, but I don't understand your thought process of pointing to the idler pulley as a potential culprit. I would think the sound would be constant if it were a idler pulley. Is it because with the AC compressor on it puts more of a strain on the engine and thus the timing belt causing the idler pulley to act up?

I'm always interested in learning more about our rigs so some explanation of why you and [MENTION=107674]JRZEE2000TR4LTD[/MENTION] think it could be an idler pulley would be much appreciated.

I really don't think it's the pulley. I'm just in the habit of checking ALL the things that can possibly be checked. With that being said, the pulley could be an issue if there is belt looseness along with a dragging pulley because when load is put on the belt, the slippage/squeal will occur on the component where there is "load" whether it be artificial load from a bad bearing or from an actual working load like a PS pump or AC clutch.

 

[LittleCaesar]

If the bearing in the pulley is on its way out but not dead yet the tension under load could cause the noise. Could, not that it is though. Similar to a failing wheel bearing or in bicycle lore, a non sealed bottom bracket, that is noisy upon initial use in the cold but ceases to make noise once warmed up.

Salt water is not kind to pulleys. If the OP has any rust on them, I'd look there as well.

 

[Kyngfish]

If the bearing in the pulley is on its way out but not dead yet the tension under load could cause the noise. Could, not that it is though. Similar to a failing wheel bearing or in bicycle lore, a non sealed bottom bracket, that is noisy upon initial use in the cold but ceases to make noise once warmed up.

Salt water is not kind to pulleys. If the OP has any rust on them, I'd look there as well.

I appreciate all of the feedback and points of view. I'm still not clear on what the idler pulley is. The diagram I saw shows the idler pulley as the same thing as the tensioner pulley. Is this incorrect? Tim also mentioned there are two idler pulleys in where the timing belt is, and wouldn't the pulleys on the crank also be idler pulleys? If someone can clarify all of that, I'd be obliged.

All that said. I think the belt on the AC was a bit looser than it needed to be, I could push it about an inch with medium pressure. So I loosened the tensioner pulley and pushed everything to slack and turned the different pulleys. The pulley on the condenser seems to be turning fine, and it has some surface rust, but it turns smooth. Same with tensioner. Moreover - where the alternator looks oxidized (aluminum) - the condenser looks fairly new. I made it all tighter and closed it all back up.

After a few hours I started the car back up and "SCREECH". Except this time the AC was off. No screech when I turned on the AC. So I looked at the belts again, power steering seemed fine. The Alternator belt seemed a bit looser than it needed to be, again about an inch of give with medium pressure.

I'll start it again in the morning and see what happens.

 

[LittleCaesar]

The bolt that you turn clockwise to tighten the belt is the tensioner itself, it adjusts the slack of the belt to become more loose or tighter depending on which way the bolt is turned. This principal applies to most engines with drive belts to drive their alternators, pumps, and compressors.

Oh yea, the idler pulley for the AC has a bearing in it where as others don't such as those on the fan bracket.

belt tension gauge | eBay

 

[s20004runner]

I didn't read any of the above comments, but if squeal only happens when ac is turned on, then I would think it was the compressor.

My idle tensioner squealed both on and off.

this tension gauge is cheap and works very well. https://www.amazon.com/Gates-91107-...rd_wg=nzl85&psc=1&refRID=14KEHYBA2KN3CYF5TQ7R

lastly, ignore the new belt tension suggested by guidebook (that's how i broke the tensioner bearing because it was overtightened) after initial tightening just remeasure after belt has been used for about an hour.

OK so i was getting a squeal on startup. It would go away when i turned off AC so it's an AC problem.

I replaced all the drive belts and the tension seems fine. I went off to visit the folks for Thanksgiving for 4 days and came back and started her up, and sure enough, squeal - it lasted a little longer than normal, and when it went away, it would occasionally squeal when I revved. In 2 minutes the squeal was gone.

I read through the old threads and they talk about the bearing going out on the idler pulley, or replacing the tensioner pulley.

I looked at the diagrams and the idler and tensioner are the same thing. Right? A new tensioner pulley is like 20 bucks and easy to replace, but how do I diagnose the squeal? When I had the belts off, I turned the tensioner pulley and it seemed to turn smooth. Obviously the problem is occasional and goes away after 30 seconds of running, but it is slowly happening more frequently.

Could it be the compressor? Do I need to worry about any of the pulleys on the crankshaft?

 

[kball]

I appreciate all of the feedback and points of view. I'm still not clear on what the idler pulley is. The diagram I saw shows the idler pulley as the same thing as the tensioner pulley. Is this incorrect?/QUOTE]

yep

 

[mtbtim]

The bolt that you turn clockwise to tighten the belt is the tensioner itself, it adjusts the slack of the belt to become more loose or tighter depending on which way the bolt is turned. This principal applies to most engines with drive belts to drive their alternators, pumps, and compressors.

Oh yea, the idler pulley for the AC has a bearing in it where as others don't such as those on the fan bracket.

belt tension gauge | eBay

I was doing research this evening to help [MENTION=102606]infamousRNR[/MENTION] replace the belts on his rig and saw the idler pulley on the AC bracket you and [MENTION=107674]JRZEE2000TR4LTD[/MENTION] were talking about. I thought you were talking about the idler pulleys the timing belt runs on and that's why I was confused how it related to the noise the OP was experiencing when turning on the AC.

As you can tell, I haven't messed with the AC drive belt yet and that's why I was ignorant of the idler pulley that tensions the belt.

Here's some pictures from the FSM showing the pulley on the AC Compressor Bracket and how to properly tension the belt:

 

[LittleCaesar]

Thanks [MENTION=120071]mtbtim[/MENTION] and [MENTION=44978]kball[/MENTION] for posting those pics. Hopefully any obfuscation the OP had before is gone.

The lock nut for the idler pulley may not be tight enough but usually the bearing in it begins to wobble due to too much slack, not enough, or just used and abused. A new one is $35 at the dealer. He just needs to understand how to put the correct tension on the belts.

 

[Kyngfish]

Thanks [MENTION=120071]mtbtim[/MENTION] and [MENTION=44978]kball[/MENTION] for posting those pics. Hopefully any obfuscation the OP had before is gone.

The lock nut for the idler pulley may not be tight enough but usually the bearing in it begins to wobble due to too much slack, not enough, or just used and abused. A new one is $35 at the dealer. He just needs to understand how to put the correct tension on the belts.

Thanks all for working together on this. As I mentioned last night, given that I was getting around an inch of give on the AC and alternator belts with medium pressure, I tightened those a bit until I was getting around .5 inch. I went ahead and bought the gauge and when it arrives I will check again.

That said this morning it started up with no squeal. It was periodic before the belt changes, and became a constant problem after the belt changes, so I am not declaring victory yet, but it looks to have been a tension problem. Not a pulley problem.