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2005 Caravan, around 160000km. Went down into town, got fuel and stopped at the store. When I started the van again it started making this terrible howling noise (see linked video).

Drove normally on the way home, sort of changes in pitch a bit when it shifts but otherwise, nothing different but the new noise (doesn't change when steering, etc).

Drove by a neighbor's on the way home, asked him what he figured, he suggested to take off the serpentine belt and try the pulleys. Loosened the belt, they all seemed fine but the idler and tensioner pulleys made a bit of a growl so went into the parts store and grabbed some new ones, plus a new belt (was a little overdue).

Changed them out, same noise :(

Any ideas??

http://www.youtube.com/watch?v=1MwyH1k3TBw&feature=youtu.be
 

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Is it from the front or the back of the engine? If the serp belt in the front is off and the noise is still there, it may be a timing chain tensioner block under the timing cover? Pull the belt splash shield for a closer listen. You took the serp belt right off the pulleys, correct? Watch for moving parts while it is running.
If the noise is towards the rear, it may be a transaxle front pump noise. The pan should come down for an inspection and fluid and filter change. Use ATF+4 only. A restricted filter can cause pump whine.
 

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Discussion Starter #3
I pulled off the belt again today and started the van, that killed the noise. It's not the tensioner or idler pulleys, they're brand new. Doesn't seem to be the PS pump since I flushed the fluid this morning, removed the reservoir and cleaned the screen and the noise it made as it worked the air out was way different.

I'm leaning towards the alt now. Seems to freewheel OK but it got hot REALLY fast when I was running it this morning to flush the PS system. Probably only ran the van for 1-2 minutes and it was almost too hot to touch!

So, going to hit a local wreckers on Monday and pick up a replacement, hopefully it does the trick.


Thanks again!
 

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Let the engine cool to ambient temperature. Remove the serpentine belt completely from the engine. Start the engine and run it for about 30 - 60 seconds. Don't run it longer because the water pump will NOT be circulating fluid through the engine block. Is the noise still present? If NO then the noise is attributable to an accessory drive pulley / idler / device driven by the belt. If YES then you have eliminated the accessory drive (water pump, power steering pump, idlers, alternator, AC compressor, etc and the noise is internal to the engine and / or transmission.

I bet the noise will disappear with the engine running and the serpentine belt removed. That model has a decoupler pulley on the alternator and those can make noise while running.

I think those decoupler pulleys are prone to failure. It is basically an overrunning clutch that allows the alternator rotor to free wheel and slow down at its own speed when the engine rpm drops significantly. A used one at a salvage yard will probably exhibit the same problem in a few thousand miles. I would buy a rebuilt alternator from an auto parts retailer with a lifetime warranty. If the alternator pulley fails again you are covered.
 

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Thanks for the reply Allan.

Any idea how I can tell if I have the 140A or 160A alt? Our van is pretty basic, not much in it so I'm guessing 140 (no vid screens, rear AC/heat, etc)
 

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burnt03 said:
Any idea how I can tell if I have the 140A or 160A alt? Our van is pretty basic, not much in it so I'm guessing 140 (no vid screens, rear AC/heat, etc)
If you do not have the optional rear heater / AC unit then you probably have the lower amp alternator ( < 140 amp). You should compare the outer case diameter of the original to the replacement. The higher output, 160 amp alternator probably has a slightly larger case ( 1/2 to 1 inch greater outside diameter)
 
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