Yes, the shims are used to adjust the belt tension. To tighten the belt tension, remove shims as needed from between the pulley halves, and place them under the pulley bolts. To loosen the tension, take shims from under the bolt heads and add between the pulley halves. As you tighten the bolts in either case, make sure to rotate the engine to allow the pulley to come together. 

Karl
  ----- Original Message ----- 
  From: Bill Johnson 
  To: vanagon@GERRY.VANAGON.COM 
  Sent: Tuesday, November 23, 1999 10:13 PM
  Subject: Belt Adjustment

  I am unsure if the water pump to crank V belt is adjustable on the 1.6 diesel.  Page 19.4 of Bentley's shows shims on the water pump pulley.  I am don't know how this works to loosen or tighten a belt.  Can anyone help?

  Bill

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