The tensioner pulley on my A/C tensioner is cracked and I need to replace it.  I purchased a new one but I am not sure how to go about taking the old one off...  I have the hydraulic kind.. i think.  There is an 8mm hex port in the middle of the pulley to retract it but I dont see any way to take the pulley off to replace it.  Also, I can't find anything in either my bentley or chilton manuals.  Thanks!