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Discussion Starter · #21 ·
I suppose that narrows it down to either AC compressor or the alternator. Any idea how I would go about ruling one or the other out?
 

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Still could be the AC pulley--that's always turning. Did you start and run the car without the serpentine belt installed?
 

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2012 Focus SE hatchback black
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The a/c clutch bearing you mean. I doubt it but of course it could be. It's only really testable by spinning it with the belt off just like the alternator. However, you don't hear of the a/c clutch bearing going bad. You do hear of alternators going bad though. Many times though you need the pressure from the belt and the speed as well to have it make noise.
 

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'....you don't hear of the a/c clutch bearing going bad...'

I strongly disagree, it's the most common reason why most compressors get changed. Most will not sell the clutches separate, you have to demand it, they want the entire compressor sale as it garners more cash. Over the years I have had several clutch bearings go in Fords including 2 in Focus cars. My Tempo, Topaz, and Contour all failed them too. It got routine enough I sourced just the bearings and changed those alone and can do it on a Focus Mk1 in under an hour losing no refrigerant. I have now even learned to simply yank bearing seal and clean the old dead lube out to recharge the grease and put it back together if bearing is still tight and running one now for years done like that. The bearings die when the grease backs off and turns into wax that will not circulate in the balls. Liven it back up and years more life there. I do the same with idler and tensioner pulleys now to save at least $20 a pop now.

Play with a/c switch on and off a bunch, if that bearing is going bad the a/c load at some point will change the noise and the difference in noise a/c on or off then tells you it is that bearing. You can often spin the clutch pulley by hand to tell too, there is a certain point where the bearing will feel weird like it is TOO loose and that is a bad bearing too even if not locking up or dragging.
 
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2007 Ford Focus ZX3 SE, 2.0L Duratec, Automatic
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An alternator bearing noise will be a constant increase or decrease with engine speed -- in gear or parked. The power steering pump noise will rise and fall with both steering wheel inputs and engine speed. You said you changed the tensioner and the idler, so alternator is my primary suspect. Stick your good ear on it. It should be a low dull hum. If you're hearing a sharp grinding noise, there's your beastie.
 
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it's the most common reason why most compressors get changed. Most will not sell the clutches separate
You can disagree but from my observations your opinion is inaccurate. One trip to the Advance website and I see the clutch listed by itself just like the complete compressor is for a 2001 Focus: Advance Auto Parts | Car & Truck Replacement Parts, Aftermarket Auto Parts, Performance Parts & Accessories
How many clutch reviews posted? 25. How many reviews posted for the whole compressor: 0.
Not that it's totally unheard of but I've never had an a/c clutch bearing in any car that I've ever owned(13 out of 15 of my daily drivers had a/c) go bad but a bunch of alternators certainly have. Most were not charging sufficiently but there were a few that were noisy too. Alternators are THE most sold major engine accessory part(alternator, power steering pump, a/c compressor, water pump, smog pump, etc) at an auto parts store. How could I know this? You're not the only one on here that's worked at an auto parts store in the past. The return shelves were usually full of alternator cores but rarely an a/c compressor made it's way on the shelf. Maybe a couple a month vs dozens of alternators in the same timeframe.
I don't know where you're getting that you have to "demand" anything from an auto parts store especially an a/c clutch. They will be happy to sell you whatever you need. Walk into one or just do what most people do and order it online. Just as easy as ordering a whole compressor and it usually costs about 1/3 or so as much.
 

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2006 Focus ZX5 SES Hatch 2.0
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If it doesn't make the sound with serp belt off that narrows it down to a pulley driven item, use the throttle link to rev the engine while standing in front, you might be able to narrow it down further and if not, you can use the old screwdriver to ear trick or a mechanics stethoscope on the pulley driven units to hunt the noise down
 

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Discussion Starter · #29 ·
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If it does it when the a/c is off even if it's less pronounced then it's likely not the a/c unless it's the clutch bearing. But that's real easy to check by loosening the belt and spinning the clutch by hand. You should also check all your pulleys this way: idler, power steering, alternator, and water pump. Listen for noise and wiggle for play.
It does seem to do it only for a few seconds after I turn off the AC. I'm wondering if it's the AC or clutch/pulley now.

Still could be the AC pulley--that's always turning. Did you start and run the car without the serpentine belt installed?
Yup I did and didn't hear anything. I do have some new info though to add since I've still been daily driving the car. The sound seems to occur as the idle hangs around 1100rpm and is 100% following the RPMs after it begins returning to idle off throttle. I've begun feeling it in the pedals when I'm coming to a stop namely the brake pedal and not so much the clutch. That part is kind of alarming to me. It's gotta be one helluva vibration to be feeling it as much as I am. It seems to also be worse on hot days which we've been getting a lot of in Utah these past few weeks.

If it doesn't make the sound with serp belt off that narrows it down to a pulley driven item, use the throttle link to rev the engine while standing in front, you might be able to narrow it down further and if not, you can use the old screwdriver to ear trick or a mechanics stethoscope on the pulley driven units to hunt the noise down
I checked all of them with my wife being my helper this past weekend when I changed the serpentine belt. I can hear the groaning and vibration in every accessory to some degree but AC compressor housing and alternator are the loudest which is interesting considering they're on opposite sides of the belt drive.
 

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Discussion Starter · #30 ·
The more I drive it the more details I have. The noise only occurs in the range of 900-1100 rpm. When I'm coming to a stop is when it begins as the RPMs fall into that range. The noise is loudest as it crosses over 1000 and slowly wanes as the RPMs settle back down to idle after a few seconds.

I've got someone taking a look at it but he won't be able to get the car in until the 29th
 
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