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Old 11-18-2007, 12:28 PM   #2
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Join Date: Sep 2007
Location: Salem, NH
Posts: 39
My Ride: '03 330xi & Alfa's
Next you need to remove the dust cap off of the AC tensioner.
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Here's an somewhat fuzzy picture of what the cap looks like.
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Now we need to make use of the T50 Torx bit. To detension the tensioner you turn it clockwise with the ratchet. If you have it as shown in this picture, you push down on the ratchet. This tensioner is not very stiff and should move easily. Mine looked to be in great shape so I didn't replace it.
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While holding the tensioner in a detensioned state you should be able to easily remove the AC belt with your other hand.
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Now we move on to the alternator (or serpentine) belt tensioner. This is where you make use of the 8mm hex bit socket. A little caution here. This tensioner is MUCH stiffer than the one for the AC belt so make sure you use a quality hex socket bit that will not round off! I used a craftsman one from Sears. You will also need a socket wrench with a longer handle as you are going to have to apply quite a bit of force to get it to move enough.

Here is a shot of the tensioner with its cap still on.
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And now with the cap removed. To get these caps off you carefully pry them off with a flat bladed screw driver. They will most likely pop off and go flying. Also I should mention that you should be careful when working down here so that you don't ding your radiator with any of the tools!
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At this point it would be wise to make a simple drawing of the routing that the belt uses around the various pulleys so you don't get confused when putting it back on!

Here I am about to detention the tensioner. Note that I put the reverse clicker on the socket wrench only so I could take the picture without holding it. This one also detensions in the clockwise manner, I found it more convenient to pull this one up rather than pushing down so the wrench is shown on the opposite side of the tensioner as compared the the AC one. As I mentioned, this one takes a lot more force to move so be careful and don't let it snap back as this could break the tensioner! Slow and steady is the name of the game here.
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With the greater force needed this belt is a little trickier to get off but you can do it! Here it is almost off snagged on the bit. Just wiggle the bit out and the belt basically falls off. Once again my tensioner appeared to be in great shape so I didn't replace it.
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Here we are with both the belts off.
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Now time to get the new belts on. First we put the alt belt on. Look at the drawing you made (you did make that drawing didn't you?) and put the belt on all the pulleys except for the tensioner pulley so that it appears as in the picture below. Once that is done put the belt around the hex bit so that you will be able to slip the belt on when the tensioner is detensioned. Now pull up on the socket wrench to detension the tensioner and slip the belt onto the tensioner pulley. Let off the tension slowly. Once that is done check how the belt it situated on each of the pulleys to make sure it is on right, more than likely one of them won't be quite right so detension it a bit again and fix the belt.
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Once the belt is situated on all the pulleys it should look as it did before you started .
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