Belt tensioner --- where is the darn thing?

expat

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Jun 1, 2010
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1994 C250D Saloon
I've got a 1994, C250D 5-cyl diesel (202) and I think my alternator has gone out on me. I'm taking it out to have it tested but for the life of me I cannot find the belt tensioner to loosen the serpentine drive belt. Can you point me in the right direction?
 
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expat

expat

New Member
Joined
Jun 1, 2010
Messages
24
Location
Near Galway
Car
1994 C250D Saloon
Found it (I think) so how do I loosen it?

Well, I'm pretty sure I found it, now though, how do I loosen it? The tensioner is a pulley mounted to a spring loaded. The rod bolts (at the top) onto the front of the engine and down below the pulley has the serpentine belt running on it. I'm thinking there is some kind of adjuster nut on the pulley but cannot figure that out. Is it possibly in the middle of the pulley? If that is the case I don't think I can do anything unless I take the fan off? Again, any suggestions?
 

Tony Russell

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Glasgow ish.
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Vaneo. 1.7CDi. I know. Stop laughing ! I need an MPV and it had to be Mercedes. OK ?
Well, I'm pretty sure I found it, now though, how do I loosen it? The tensioner is a pulley mounted to a spring loaded. The rod bolts (at the top) onto the front of the engine and down below the pulley has the serpentine belt running on it. I'm thinking there is some kind of adjuster nut on the pulley but cannot figure that out. Is it possibly in the middle of the pulley? If that is the case I don't think I can do anything unless I take the fan off? Again, any suggestions?

Is it not one of those ones where you need a "special tool" (or an 11mm ring key) to pull back the tensioner arm a bit ?

That's the case on mine (different car mind ! )- it's a very strong spring, so you'd be forgiven for thinking it's solid.
I used a bit of an extension to give me some purchase on the spring.
 
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expat

expat

New Member
Joined
Jun 1, 2010
Messages
24
Location
Near Galway
Car
1994 C250D Saloon
It is a pulley, just about out of sight, and then there is a spring arm with a hook on one end that hooks into the pulley. The spring arm is about 7" long. At the top of the spring arm is an eye where you run a bolt through to secure it.

I removed the bolt and released tension on the belt. Now the question is, when I put everything back is there a trick to putting vertical pressure on the spring to stretch it enough so that it will be easy to run the bolt through the eye at the top of the spring arm?
 

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