the mystery of the 190d belt tensioner

[robparker]

I must be missing something really obvious here.. this is on a 190d 2.5 (OM602, same as 603)

Its the girlfriends car, i noticed when topping the oil up that the v-belt was only half on the tensioner pulley and visually you could see the tensioner was right on the pi$$. Infact the belt was just about fouling the fan blades. So as a temperary measure I remove the fan blades as they are not needed anyway.
Next chance I got I found a used tensioner and fitted it and again you could see it was bolted on on the pi$$ still, needless to say as soon as it started the belt jumped straigh back to its half-on position. I have a friend that works in GSF so I 'borrowed' a new tensioner incase it was the bearings in both the old ones gone sloppy and I didnt even bother starting the engine, this tensioner was also on at an angle. I have now refitted the origional again and left it how it is, just waiting for the belt to snap...

 

[Alex Crow]

As you probably know, it is usually the tensioner arm.

Could you have cross threaded the pivot bolt?

 

[robparker]

I dont think so as it screws in and out by hand most of the way until it needs tightning at the end, but that does seem like the only answer as there is no bush or washer etc between the arm and the block where it screws in, so I dont know

 

[Alex Crow]

Errrr...there is supposed to be a thick washer behind the arm, that traps between the shoulder on the pivot bolt and the front case - if missing that will put the arm back, and out of line.

 

[robparker]

hmm, both new and old ones dont have anything seperate, just whats attached to the unit, I wonder if the one originally on the car disintergrated to nothing, I have no idea how long its been like this for, i'll see if there is a seperate washer available from MB.