Alternator Swap, Loose Belt, Help!

I put in a new alternator today and need help getting the serpentine belt tight. The Bentley says "turn hex clockwise" to pretension the belt, then tighten the idler arm bolts. I don't know what that means. The tensioner pulleys have a 45 torx bolt if that helps. I also have a tensioner pulley to the lower right of the alternator that doesn't show up in the Bentley or any DIY's I've seen.
How do I get the belt tight on an '02 540? It's on, but squeals at me. I also broke a fan blade, broke a pop pin on the fan shroud, and caused an oil leak by the oil filter housing. But the alternator works!

Originally Posted by russelltickle

I don't know what that means.

This is one job that, apparently, almost nobody understands in words (me neither) until you do it once, or, until you see the pictures.

I'd start here for references of what it looks like as this question has been asked a few times recently so your best best is to start where everyone else left off.

- How to tell if you have mechanical or hydraulic belt tensioners (1) & how to switch from mechanical to hydraulic (1) and what is the difference between the two types (1) (2) & how to rebuild your hydraulic tensioners (1) & the answer to the question of adjusting the 540i hydraulic tensioners' belt tension (1) (2)



This next screenshot kindly supplied by QSilver7:

Blue,

Thanks so much for that, those pics are very helpful. I'll give that a try.

Russ

It's more likely your belts are on wrong though.

It's easy to wind them on the wrong way (ask me how I know).

The Bentleys will have the diagram for you to follow.

With the help of that picture and description tightening the belt was easy. I replaced the broken fan blade and stopped the oil leak (filter housing cap was loose) and am back on the road. Thanks again.

Originally Posted by russelltickle

tightening the belt was easy.

Glad it turned out to be easy as others have asked this before.

For the benefit of others, and especially since many of us don't have the V8, would you mind writing a short post that describes 'how' you ended up tightening the belt?

That will add value and help others.
TIA

I'll be glad to describe what I did but please keep in mind I'm no expert. I replaced all the rollers and the large belt tensioner, which was only finger tight at the bolts. The belt then goes on and has a couple inches of play in it. I found it easier to route it from under the raised car with the splash shield and fan removed. Some do it with the fan on, but I found this difficult. The large belt tensioner now has some mobility in it, due to the slot near the lower 13mm bolt. When you push down on the arm the two rollers move down and put tension on the belt. I found this part easier standing over it. The issue is holding it down while tightening the lower 13mm bolt. The trick is to put a 17mm socket on the cast in (part of the arm) hex (bolt) and turning it counterclockwise. This moves the arm down, puts tension on the roller, and holds the whole thing down (bottoms out the arm on the lower 13mm bolt slot). Now you can put a 13mm socket on the lower bolt and tighten it, while holding the 17mm socket tight with your other hand. It takes two hands, but isn't difficult. An extended 13mm socket helps. The last step is to tighten the other 13mm bolt that sits above the 17mm cast in bolt. The Bentley shows a pre 8/97 set up that has the slot at the top of the arm rather than the way mine is with the slot on the lower end, like in the photo above. I'll welcome any tips on improving the way I did it.

Originally Posted by russelltickle

I'll be glad to describe what I did

Thank you for that wonderful description.

The good news is we can now, in the future, point people to your post for them to begin where you left off and improve the process from there.

Everyone stands on the shoulders of those who have been there before them to break new ground.

thanks for pitching in.