Replacing AC, Alternator, etc. Belts - 380 SL
 

Would like to replace all belts - a few are showing cracks - on my '85 380 Sl.
Are there any lurking problems or is it as straight forward as it looks i.e. Loosen belt tensioner and all adjusting and holding bolts on the relevant components. (Note- car has no airpump belt - has not been connected for years.)
Thanks. Any advice to minimize problems appreciated

Sometimes after you loosen the belt tensioner to replace the belt, it won't tighten up again. A common problem, so be aware.

What is the fix ? Do you need to replace tensioner ? C

On my engine, ( after putting on a new belt ) I needed to replace the tensioner and a small gas filled shock absorber attached to it. I suppose that the tensioners get weak when old and after they get relaxed when you take off the sepentine belt, they won't hold a high tension when you go back to tighten them up. My car is 23 years old and 110K miles.

Your 380SL is a 107 model and have no gas tensioner or serpentine. The adjusting tensioner is mechanical and should have no problems re-adjusting when belts are replaced.
You will need following V-belts part numbers:-

2 X A0069976092 9.5X1100 power steering pump/water pump
1 X A0099975292 9.5X990 Alternator
1 X A0069976292 12.5X930 Refrigerant compressor
1 X A0069972492 9.5X750 Air pump

May I ask why the air pump is not connected? You would benefit by reconnecting it. As you mention, you release the tensioner pulley bolt, alternator and power steering pump. Replace the belts and tighten them accordingly. Hope it helps.

Did you check the on line service manual?

Car has 87K miles and runs very well. (only used during summer) Was purchased in 2001 with 54K and disconnected air pump. 60k service performed by local MB mechanic and no recommendation for connection of air pump was made during the service. What would work better with pump connected ?