OM651 924 Timing chain / tensioner

[Vanbursta]

Is it possible for the timing chain to be running directly on the tensioner in an OM651 924 2.2 engine? I replaced the old one (single hole) with the latest 4 hole version and 2 things bothers me,

1) The new tensioner went in very easily, it didn't seem to hit the guide until it was about half way in (last car I did this on was very difficult because of the spring pressure) and
2) Looking at the old tensioner, the wear marks look like the chain is running directly on the head (see pictures)

Any advice here would be good

.

 

[Eazyd123]

Hi,

Do you have any guide on how to change the tensioner? I have a CLA 200d and would like to change it.

Thanks in advance

 

[Vanbursta]

Certainly, please see attached PDF file

 

[Oleks1992]

On cla and a class the tensioner is on the back of the cylinder head in the passenger side. A bit awkward to get to but not too bad

 

[Eazyd123]

Amazing! Do you happen to know if I need to lock the cams or is it as simple as remove old and insert new (once primed with oil)?

Thanks

 

[Oleks1992]

Amazing! Do you happen to know if I need to lock the cams or is it as simple as remove old and insert new (once primed with oil)?

Thanks

Just set the timing to tdc and replace it Although usually new tensioner is a short term fix. Eventually rattle comes back and you'll be doing chain and tensioner anyways

 

[Eazyd123]

I don’t actually have a rattle on start up. The main reasons for wanting to change are 3 things
1. When driving I can hear a faint rattle sound which is more predominant when accelerating I can only describe it as a marble in a jar type rattle ( if that makes sense).
2. I’m not sure if it has the new version with the 4 holes.
3. Peace of mind

What’s your thoughts?

 

[Tonygw]

A loose/worn chain or worn tensioner will be heard at start up, usually cold starts and will last a few seconds. It will make a loud clack clack clack sound. or sometimes a similar sound to tapping on an empty food can.

There is a lot of things to rattle on the OM651 engine. A common rattle is the turbo waste gate, mine rattles and then suddenly stops. its the metal connecting rod to the waste gate. They all do it and its no noise for concern.

There is also a lot of plastic and moving parts that can rattle. Even the plastic cover rattles on mine. if I press on it, it goes quiet.

If its the chain you would know.. (if you know what I mean)

I am of the thought that if its not broken don't try to fix it. Personally I would leave the tensioner in place until you notice the chain rattling, which you may never as many don't suffer at all. Some say its the over use of the stop start system that causes chain issues on the oM651.

But generally they are a tough engine.

 

[Eazyd123]

Thanks @Tonygw.

I wasn’t aware of the wastegate rod making noise but this may well be the cause. To be honest I remember having a BMW F30 320d N47 engine hearing a similar sound prior to the chain/ guides being worn and had it gave me the shivers!!!

Thanks for your reply bud

 

[PEHARDMAN]

Hi all I have a, from now, 2014 S212 E class 220CDI with 245k miles (it’s been almost faultless to-date). Occasionally on cold start up I get a loud rattle for a couple of seconds, having read up I have bought a OEM tensioner to fit. On the face of it it seems an easy enough job to change it, my question is do I need to set the engine to TDC or not? If so how do I set the engine position to TDC? Has anybody got the Merc procedures for changing the tensioner etc.
Thanks in advance.

 

[Oleks1992]

Hi all I have a, from now, 2014 S212 E class 220CDI with 245k miles (it’s been almost faultless to-date). Occasionally on cold start up I get a loud rattle for a couple of seconds, having read up I have bought a OEM tensioner to fit. On the face of it it seems an easy enough job to change it, my question is do I need to set the engine to TDC or not? If so how do I set the engine position to TDC? Has anybody got the Merc procedures for changing the tensioner etc.
Thanks in advance.

Hi there, yes you'll need to set engine to TDC. There's OT mark on crankshaft pulley and if you remove camshaft sensor on cam cover there's a line in camshaft to align. Although from experience new tensioner is a short term fix. Rattle will come back again and you'll have to do the chain anyways.