AC Compressor or alternator pulley

[jettajim]

Car: '00 Jetta TDI, auto with 177k
Symptoms: 'clattering, vibration type sound' when AC on. When the ac is turned off, the noise goes away sometime not instantly.

Here's what I did:

- removed belt and turned the alt pulley in both directions--it locked in one direction as it should

- Replaced ac coil and ac clutch but this didn't change anything

- Replaced ac pulley bearings and this worked for about a day now the sound is back

Before I did anything, with the engine running & my wife in the car, I was under the car and watched the ac compressor. When the 'noise' happened, the ac clutch stopped. This is why I thought it was the clutch.

Since the noise is still there after doing this stuff to the AC and checking the alt pulley, I think I have a bad compressor. I changed the compressor once before at ~90k.

Is this the only way the verify that the alt pulley is good or bad?

I want to here your thoughts before I do anything else.

I appreciate it!

Thanks,
Jim

 

[gquenstedt]

If the alternator pulley locks in one direction and free spins in the other, it is working as designed.

What is the history of the a/c system? You say you replaced the compressor, did you also replace the expansion valve?

 

[jettajim]

Yes, the expansion valve and dryer were changed.

Thanks

 

[ninedee_golf_tdi]

Are you sure the serpentine belt tensioner isn't kaput ?

 

[jettajim]

You know, I never thought of that. I have a new one that I was going to install on my '01 Jetta. I can put it on the '00 instead.

That may be the problem because the 'noise' starts at a certain rpm.

But here's the kicker that I forgot to mention: It NEVER makes the 'noise' in the AM. Or at idle. I'll have to check the mileage on the serp belt and the idler pulley.

Perhaps the little bit of stretch in the belt due to the high temps we have here in Houston and in combination with a weak idler pulley is enough to do it.

Thanks for the idea!

 

[vic_seadog]

You know it is kinda strange, I have the same problem but mine is noisy when idling. I have to go to Dealer to check it out, I can smell big bucks going out of my pocket.

 

[2jettasinthedrive]

Is it making the noise after the bearing Heats up? Does it hop while running? How about the little piston/shock absorber thing, is it leaking?

 

[vic_seadog]

My "hops", furthermore, I went to VW Oakville yesterday and mechanic looked at it and he said that it is definitely alternator pulley. He also said that it is very common in PD engines, they actually had 3 cars with the same problem in shop.