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Discussion Starter #1
Just picked up a 2004 Jetta GLS tdi. Its a 5-spd. I noticed when driving it that theres a noise, best described as a high-pitched squealing sound (like air being released from a balloon with the mouth stretched to the sides), whenever your foot is OFF the gas. Once you touch the gas the sound goes away. It sounds like its coming from inside the car, under the pedals. When I was poking around in the engine bay it sounded like it could be coming from the brake booster area, maybe a vacuum leak? Can anyone provide any insight? Thanks guys!
 

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If it's not a vaccuum leak my total guess: alternator pulley clutch. The sound you describe is normally associated with belt noise. The alternator has a one way clutch in the pulley the belt rides on. At idle there may be a condition which causes it to slip. Take the serpentine alternator belt off and spin it by hand. It should move freely in both directions. Now take a wood or plastic dowel (not metal to avoid damage) and stick it in the alternator fan inside the alternator to jam it. The pulley should rotate one way and not at all in the other. There is no noise that I can think of inside the cabin which would cause this type of noise. To replace it, you need a metalnerd.com special bit (cheaper than VW tool) to counterhold it, assuming it is the problem.
 

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Discussion Starter #3
I'll check that out, but it sounds really close to inside the car. Not sure if theres any relation, but my cars been trying to bog down alot and stall when I come to a stop.
 
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