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Discussion Starter #1
i first thought the worst, spun rod bearing; but it went away when i pulled over to look at it, which in my experience doesnt happen wth crank bearings when they spin. Then it started again and this time continued while i had the hood open. I used an extension to and my forehead (dont judge, in a pinch its an excellent mechanics skope) to check for resonance from the case and it was super smooth and no knock but then I checked the alternator and it was knocking pretty hard, ....odd. so I shut off the car then turned it back on to make sure the sound was still there (as it had up to this point been not coming on until the car got up to 40 + mph). I shut off and back on and the sound was still present. so i went with a theory and removed the alternator / power steering belt and then I restarted the car, sound went away completely, then got the belt put back on and the sound was back again. So that kind of isolated the problem down to either the power steering pump or the alternator. Since I had both of these parts on my parts car, I swapped them and the problem has seemed to go away, but not completly. the sound is all but gone, but the alternator seems to still be vibrating way more than three other cars I compared it with (though none were subarus). I have a long trip ahead of me to north dakota and Im a little reluctant to trust in my faithful little subaru when it does things I cant explain.
so any help is appreciated as I am supposed to leave tomorrow.
Also the alternator gets really hot when compared to the motor case or the intake or the ac compressor. I dont know if thats just normal because of the nature of the alternator but i thought I should mention it.
The power steering pump that was on during the sound problem had been leaking and going out in general so i replaced it too at the same time, but the sound and vibartion seem to be coming from the alternator so i just cant be sure.
also I added a single heated seat to the drivers side so perhaps placing too much load on alternator. do they have different alternators for different options??
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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It could be the effect of the extra load. It could be worn bearings in the alternator. A way to check the bearing without disassembly is to remove the belt and spin the pulley by hand. If the noise is there, its not due to the load.

Alternators will get hot. The magnetic field within creates heat as do he bearings. Then you have the placement of the alt on top of the engine which allows it to gather more heat. The heat isn't an issue unless it is so hot you can't touch it.
 

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OBW H6 VDC, Tribeca, XT6
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you can do the remove-the-belt-trick again, do it multiple times to verify. once can be kind of hit or miss.

a mechanics stethoscope on the alternator casing and engine may isolate the source.....but without another vehicle to compare it too you might have more questions.

if you have an IR temp gun you could post temps and ask someone else with one, like myself, to post our temps and compare.
 

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Discussion Starter #5
The knocking sound went away when I replaced the power steering pump and alternator, though the alternator (it would seem) is kind of vibrating with a slight knock now, but its definitely quieter and less pronounced with those two parts from the parts car.
Timing belt tensioner is brand new as are all of the idler pulleys and water pump etc. i redid them all when i swapped the motors.
 
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