1978 280SE Alternator replacement - A question!?!?

[BenzGmarket]

Ok,
I know changing an alternator is usually pretty self explanatory and should only take around 45 minutes (on American cars anyway).  This is my first MB and the story is not the same.  The alternator on this car is evil.

Is there a tensioner pulley? I finally removed the alternator after about two hours. I cut the belt to remove it (it needed a new one anyway).  So now, I have the new alternator, and the old one off of the car.

What is the best way to go about putting it back on?  How do I get the belt back on?  Do I need to loosen one of the pulleys to get the belt back on?

I searched in the W116 forums but didn't really find anything. 

Any help or links to instructions are appreciated.

[oscar]

To retension the belt - facing the radiator you'll see a rack and pinion type set up for the adjusting bolt with toothed wheel which moves the alternator backwards and forwards to tesnion the belt (1st pic).  But in order for this to work you have to loosen 3 other bolts/nuts.  There's one nut on the rear side of the tesnioning bolt (2nd pic) then there's two more bolts or a bolt/nut combo on the underside of the alternator that make up the hinge joint.  The third pic shows the forward facing bolt of the hinge.

NB: this is in a car without the aircon compressor obstructing the top view.

If all else fails you could try this VW trick  http://www.youtube.com/watch?v=BQhfcdQf1QA

[BenzGmarket]

Excellent!  Thank you very much Oscar....

[gerardoparedes]

The rack and pinion bolt in the alternator is a cool measure, not bad for 70's technology, i removed mine and resolder the cage a few weeks ago, about 15 min with the right sized ratchet extensions.

[oscar]

Glad to hear it only took 15 mins.  I haven't had to take one off, just replaced belts is all and can't remember how long it took me.  Probably all day  

One thing I've noticed is that there's a similar rack and pinion bolt for the power steering pump but on the three remaining 280's I have, all mine are mangled as though someone's tried to adjust the tension of the PS belt without loosening all the other clamping bolts and nuts.  There's a couple of different verions of PS pump and reservoir setups but they all seem to use the same setup to tension the belt.  It's a real PITA to try and adjust the tension when there's teeth missing fom the pinion.  Furthermore, I remember reading someone in the US buying the replacement pinion geared bolt some time ago, only to find it was too long maybe and wouldn't fit, but that was the only replacement bolt available.  Something like that and I can't remember if they were able to adapt it or not but it's something to beware of if anyone's replacing their PS belt.  Make sure the other clamping bolts/nuts are loosened so teeth don't get ground off the pinion.

[BenzGmarket]

ok, originally I cut the belt off the alternator because it needed to be replaced anyway. Now I have the alternator on, but I am trying to figure out how in the hell to take the other two belts loos so I can remove them.  You said something about a rack and pinion on the power steering as well so I will check it out.  How do I loosen the belt that goes around the a/c compressor?

I have never had such a problem replacing an alternator.  Not sure why they would put a common replacement part in such a PITA spot. 

Any help would be appreciated.

Rob

[oscar]

Man, you caught me just before I was about to hit the sack.

Yeah have a good look around the power steering pump/reservoir for bolts you have to loosen.  The adjustment bolt is either facing the front like the alternator does or underneath and could be an allen bolt.   Been a while since i looked.

But for the air con belt, adjustment or loosening that belt is by way of moving the idler pulley.  The pic below is one of Carl Jones' from this post Linkand shows just the bracket with pulley removed.  You can see a slot in the bracket so that the 'axle' of the pulley can move left to right.  To make that adjustment you need to turn that bolt head that's on the right of the picture on the bracket.  It turns a thread which slides the pulley back and forth.

I cannot remember if there's a clamping nut or bolt for this pulley.  I think there is but I can't remember what I did

[s class]

Loosening the A/C belt is easy.  First, loosen the in-hex bolt in the centre of the idler pulley by 2 turns or so.  Then screw the threaded adjustment on the side clockwise to allow the idler pulley to move inwards loosening the belt.  The adjustment screw has a 10mm head.

[oscar]

That's sooo much easier to understand sclass.   

[s class]

Well thanks to you for the pic oscar, I was too lazy to find a pic.