I have the tool to release the belt tension on my MCS. ive not spent much time on it but i can easily see how to release the tension on the accessory belt.
my bentley manual says to 'lock the tensioner and remove the old belt'
but doesnt make any mention as to HOW to lock the tensioner arm.

the manual does show a picture of a sort of "key" ...looks like it should be inserted in a hole.

so how do i lock the tension arm in place

 

You can either use a tool, or a small screw driver. You just have to release the tention, and then stick it in there to "lock" it in the released position.

 

is in the metal that comes up through the tension spring as you take the load off the belt. As you compress the tensioner more and more, there are two (I think) holes that will be exposed. Just stick something strong enough through there and it will hold in place.

Matt

 

Sorry for the poor picture but:



If you look to the "top" of the tensioning spring you will see what looks like a "T" and a piece of wire. That is the lock engaged with a piece of coat hanger.