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We recently replaced the alternator, water pump, timing belts and timing belt tensioner on our 1991 164L. Now there's an extremely high-pitched whine coming from the water pump end of the engine. I know what power steering, throw-out bearing & transmission whines sound like, and it's not any of those. It's almost a whistling sound, and is most noticeable when under acceleration.

I think this noise started after we retightened the alternator belt (because it was squealing). I'm wondering could it be the tensioner on the air conditioner compressor?

I remember asking about this before and Alfisto Steve gave me a trouble-shooting guide, but I can't find it again on the forum, despite an hour of searching.

Thanks for any help.
VM
 

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A/C compressor pulley has a bearing inside it that could be going bad or alternator bearing could be going bad. Did you change serpentine belt for water pump and a/c compressor and the serpentine belt pulley which has a bearing in it?

If you loosen serpentine belt pulley arm and remove belt from engine you can run just engine to be sure noise goes away.

Then if no noise test water pump pulley by hand as well as serpentine pulley. To hand test alternator and a/c compressor bearings you pretty much has to do test by hand too.

You may have to loosen 4 alternator bracket adjusting bolts to remove belt tension for hand testing.

Really no easy way to test running except with serpentine belt on and tight.
 

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Discussion Starter #3
Thanks for your quick reply. We replaced all the belts, but did not replace the serpentine belt tensioner. Since the water pump and alternator are new, I don't suspect them. The air conditioning compressor is maybe 5 years old. So the oldest component is the serpentine belt pulley.

We don't hear the noise when the engine is idling, only when revving under load, so how do I tell if a bearing is bad, testing by hand? Would it feel a little rough?

Thanks again.
VM
 

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Thanks for your quick reply. We replaced all the belts, but did not replace the serpentine belt tensioner. Since the water pump and alternator are new, I don't suspect them. The air conditioning compressor is maybe 5 years old. So the oldest component is the serpentine belt pulley.

We don't hear the noise when the engine is idling, only when revving under load, so how do I tell if a bearing is bad, testing by hand? Would it feel a little rough?

Thanks again.
VM
Yes spin bearing pulley by hand.
 

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If the bearing is still ok and smooth turning, you might consider having the lube replaced in it, as the OEM lube will eventually disintegrate with heat and time. Jason (Alfissimo) can do this for you using DuPont Krytox, an aerospace lube designed for high temps and high loads, which this bearing sees in real life. The engine bay temps of the 164 run quite high, and certainly tests the limits of the standard "room temperature" lube in the OEM bearing. People do use pulleys from other vehicles, but they all seem to use the standard room temp lube, so I don't really believe they offer the same long life as the relubed versions.

I had him do one for me (will have another one done one of these days) after I had a standard bearing disintegrate in the middle of nowhere on a road trip, and the new relubed bearing has worked for a few years without problems. DuPont feels this lube should last longer than the car.
 

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will add to this

In addition to good bearings and the best grease, proper pulley alignment, etc it has always been my practice to run serpentine belts at the loosest possible setting that does not squeal at start up or slip. You might try re-tensioning the belt to see if that helps. Have seen many gorilla-adjusted belts that are tuned to 'high C sharp' that simply put excessive force on the bearings === when 'low A flat" is adequate (this is a musical note reference not anything that has to do with mechanics for those not familiar!)
 

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That's what I do, to adjust the belt so that it almost starts to squeal a little on a cold start with the a/c on. Takes a couple of tries to get it right, but works well. This belt as well should have been a toothed belt in order to save bearings, not having to tighten it much at all since you wouldn't have to worry about skipping as with the timing belt.
 

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That's what I do, to adjust the belt so that it almost starts to squeal a little on a cold start with the a/c on. Takes a couple of tries to get it right, but works well. This belt as well should have been a toothed belt in order to save bearings, not having to tighten it much at all since you wouldn't have to worry about skipping as with the timing belt.
Now that WOULD be nice, wouldn't it... A toothed belt auxiliary drive! I remember seeing that for race engines (toothed belt and pulley kit). Usually just for water pump and maybe alternator, I've never seen one for a 'road' engine with power steer and a/c... Maybe with CNC machining we could design a kit! Could we use nylon pulleys... lighter and kinder to the belt.

Toothed belts however were not without noise problems. I haven't had it on an Alfa V6, but on the FIAT SOHC engine (you know the one; from 128/X1-9 through to Uno/Uno Turbo, Tipo, and Punto) I found that belts tightened to the usual guideline (90-degree twist just possible on longest run) would make a whining sound just as described in this thread. In the 90s the tooth shape changed to sort-of-round (actual Gates description) but that didn't seem to change the whine. Eventually I began to set belts less tightly and now I just watch the long run of the belt with the engine running to make sure it's not so slack that it's whipping more than a millimetre. This is the cambelt I'm referring to, of course.

The serpentine belts - I do have trouble with those, I have found a change to Bosch solved noise and stretch problems.

I actually prefer the old-style V-belts as used on pre-91 164s. Cheaper and trouble-free unless pulleys are misaligned. Probably have reduced torque capacity and reduced service life, plus take up a little more space due to simpler belt runs and doubled-up pulleys, but they work well for me and are more readily available.

-Alex
 

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The original Dayco belts don't seem to grip as well as the Gates belt that has an intermitant rib
 

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Discussion Starter #10
Hi everyone!
I can,t believe all the great responses you gave. I,m in my other life right now, at an international bead show in Wisconsin trying to sell beads to support my car habit. Will get this figured out when I get back. I totally understand the musical note thing. I think the belt is overtightened, but the bearing could need lube... I,m not used to a car running as hot as the Alfa.

VM
 
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