[fishon]

I have a 06 jetta TDI the serpentine belt is jumping quite a bit. Does any body know what is causing this?

 

[chittychittybangbang]

Very possible: bad alternator pulley clutch. Remove the serpentine belt and stick a soft wood stick to jam the alt fan. The pulley should only rotate 1 way. If it rotates 2 ways replace it. You need a special tool to loosen the pulley which can be purchased at metalnerd.com.

If not, bad tensioner?

Also, post moved to mk5 technical section, and title edited to add year.
welcometomyturbodies

 

[fishon]

I held the fan from moving the pulley did not move at all. Are all pulleys clutched?

 

[chittychittybangbang]

No, just the alt pulley. Possibly a bad tensioner. Otherwise, is your crank pulley off? What service did it recently have that may have affected it?

 

[50mpg]

Normally it's a weak tensioner.

I held the fan from moving the pulley did not move at all. Are all pulleys clutched?

Are you saying the pulley only rotated in the correct direction? It could be a bad bearing in addition to a bad clutch.

 

[fishon]

I held the alternator fan from moving the pulley would not move in any direction. The tensioner has cracks in it. I am going to replace the tensioner and the pulley. Thanks

 

[chittychittybangbang]

AH, ok, I misunderstood. Your alternator pulley is definitely bad than.

Take a look through your owner's manual and the 2005-2006 new buying checklist in the FAQ section for other stuff you may not be aware of.