Yes, both of my pulleys are smooth. That's what I don't get. That top pully should be grooved as its on the inside of the belt. No oil leaks on the belt. I think its just a result of 150k miles of the belt ribs rubbing on the (formerly) smooth pulley. Others seem to have the same result of grooves wearing into the pulley.Nilknarf,
I suspect both of the pulleys you have are smooth. The one with the buildup is really just belt material.
Do you have any oil leaks going onto the belt or the pulleys? Might be a reason for the material transfer.
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