Ok, I really thought this would come up in search, so I must be doing something wrong.

I am replacing all my belts after the alt belt failed today. I have everything figured out except the AC belt. Its over the crank, then a tensioner looking thing then the AC.

So first question is if that arm with pulley it rides over is a tensioner? If so, mine is stuck it would seem. Although I have not used blunt force yet. Did not want to incase its not spring loaded tensioner.

And if its not a self-tansioner, is the bolt that seems to hold the arm in place the one to loosen? Again, did not use full force yet incase its not.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Got it.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Please post what you did in the event someone searches for this at a later date.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Well I was not sure if it was a spring loaded tensioner or just a pulley on an arm. If it was a tensioner, it was stuck and would have to come off anyway. So I just went ahead and cranked down hard on the holding bolt on the front. Once free I it moved. But I went ahead and removed it to lubricate the pulley itself by putting oil along the bearing seat and letting it sit while I worked on the rest.

Actually getting to the bolt to loosing things up is a pain on this car! Quick run down...

PB Blaster on all the nuts before you start!

A novice may want to remove the fan blade assembly. As with most engines with multiple belts and a fixed fan, all you have to do it put the belt over a blade of the fan and keep working it around the blades. It will easily get around.

If you are committed to installing new belts. Just cut the old ones off Then you dont have to work them around the fan.

The Alternator has just one nut that has to be loosened and is easy to get to. On the front and to the outside you will see a nut with a "gear" behind it. On the other side of that nut you see another behind the alt. Just loosen this one and you will see how the front one operates and how to tighten/loosen things up.

The AC belt is only tensioned by the metal arm/idler pulley. Just loosen the large but at the base of the idler arm and it will swing free making the belt easy to remove. The pulley should be checked for bad bearing! Make sure it spins free and quietly! If not, its a good time to replace it.

The Power Steering/Water Pump/Fan use two belts that are the same size. I assume since these are critical systems its for redundancy. These belts are removed via the power steering pump. There are three nuts to loosen. At least i did three. Facing the pump you will see one at upper left. This is a pivot point and just barely needs to be loosened. In fact, one might not even have to once the others are freed up. Then there is one below that which rides in an arch guide. Very hard to get to, try from below. The last if to the right and can be hidden by lines. I took my SLS fluid tank and removed the three holding screws soI could move it around a bit. Helped a lot. This nut is also on a bolt in a arch guide. One may think that is it! But not. Above that last nut there is a screw with an allen type head. You need to unscrew this VERY far. It is used to loosen and tighten the belts by moving the pump. So as you back it off you will find the pump can move more and more along the arch guides. The hosed may want to push on it, so push down when removing/installing the belts.

The air pump belt I just cut off. So your on your own with that one. But it is the first off/last on. I dont plan to install a new belt unless I need to.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Hi there, just wondering how you managed to tension your a/c pulley when you put the new belt on. Are we meant to lift the pulley up with a lever and then just tighten the allen nut. Seems odd then there is no toothed guide to make tension. I noticed the a/c has a nut that has a 17 on it and was wondering if that might shift the a/c to tension. Any thoughts would be great.
Thanks Sam

Sam,

I use a 7/8" wrench or adjustable wrench to fit on the end of the arm of the tensioner, then loosen that 17mm bolt that secures the arm to the engine and lift up on the arm. Hold the desired tension and tighten the 17mm. The allen nut isn't involved.