W124 adjustment nut?
 

Hi guys,

I was just checking my water pump and replaced some sensors when I saw this "nut" had broken off.




1. What is it?

2. Should I replace it ASAP.

I suspect the my mechanic has broken it when he replaced the tensioner pulley not too long ago....hmmm.

The car is a 230CE

Best regards from Copenhagen,

Christian

That looks like the tensioner adjuster. Could be bad news.

I am not an expert on this but I rather think you might need a new tension adjuster (not the tensioner itself). I would guess that someone tried to adjust the tensioner rather aggressively without loosening it. Only a guess, though.

Make sure you get this resolved by a Mercedes expert and not a "normal" garage.

Best regards from Paris.

RayH

That is what I thought, Ray.

I guess it runs fine with the broken rod untill next belt adjustment, though.

Merci,

Christian

It is easy to change this. And do it! Because the belt make an hell of a noise. Make shure that you loosen the bolt for the belt tensior, before you adjust the belt.

I agree it needs to be changed however if the belt is currently adjusted properly I would not be in a huge rush to fix it.

I'm kind of curious how he got the belt adjusted with that broken?

Here's what you are looking at
https://farm3.staticflickr.com/2567/...e06bf83c_o.jpg

Before attempting to adjust this you need to loosen a 19mm bolt
https://farm4.staticflickr.com/3370/...1aa55f5b_o.jpg

While you have tension on the serpentine belt there should be no problem. The first time that something need to be done in that area you will need a new tensioner adjuster.

Could the nut have broken off after it was adjusted?

I think that nut is what holds the tensioner in place.

quick fix suggestion
 

Some months ago the tensioner on my 1990 300e broke, the result a loose belt and lots of noise from the belt slipping.

The tech info section has an excellent, fully illustrated, step by step guide to change the tensioner, altough it looks complicated, it's really easy and should not take more than a sunday morning to do.

In my case I could not get the piece here, so I improvised by removing the tensioner shock absorber and replaced it with a piece of threaded rod fixed at the lower shock mounting screw and adjusted by a set of nuts at the upper part of the engine, it works great!!.

if you want pictures, feel free to request them.

CHECK POST FROM 11-22-2013, FOR BETTER INSTRUCTIONS AND PICTURE
good luck