I replaced the tensioners in the engine in my 240D. I did it in the car. I had to remover the cam sprocket to get the one on the tensioner. The bottom two, I had to remover the vacum pump. On of the new bottom ones didn't fit, so I had to reuse the old one. I used new pins. I used a threaded bolt and nut to get them out. I would say the bottom two of mine were still good and probably the top one. The top one is easy to change. One guy told me if the chain gets sloppy, the flexing of it will take out the top one. The tensioner one had about 1/16 inch groves in it. My Odometer shows 250K, I think the car has nearer 300K on it. I had about 10 degree of chain streatch.
Tom