Mercedesa.Net

How to check if chain is stretched, only by tensioner? I'm not seeing oil hole on the tensioner(attached photo)
What's the symptoms of stretched chain?

Plutoe

Do us a huge favor---what do you think is the function of the "chain" and what do you think is the function of the "chain tensioner"??

Mercedesa.Net

I think, you are not so stupid, so you can understand what I mean. It's a forum, everyone can ask for help/information. If you search in forum, you will find more posts with same terms.

If i'm talking about enigne, timing chain, tensioner... and after all I'm posted photo, i think it's clear what I'm talking about.

If you have any idea, and want to help, please... else, don't spam.

Renato66

If you see the piston portion (shiny) of the chain tensioner it means your chain is stretched and the chain tensioner went past it's stop. The stops are 4 small notches on the body and prevent the piston from extending too far out. After the chain stretches past certain length the piston pushes past the notches and you see the shiny portion of the piston. That is why if you just put in a new tensioner the noise becomes more pronounced. You need to change the chain and tensioner.
I just did my chain and tensioner. 2012 R350 with 90K miles...
Hope this helps... good luck

Callisto1

In the photo attached by the O.P., is the shiny band just above the threads on the piston what you are referring to? If so, I guess I need to change my chain & tensioner, even though I have yet to hear the telltale rattle at cold start. Because mine looks just like the the photo he posted. FWIW I am at 71k miles on a 2010 GL350.

Renato66

Yes, if your chain tensioner looks like mine (photo attached) it is stretched. If you don't hear knocking during cold start it will come soon.

Callisto1

Great photo! And from that it looks like I have some life left in mine. But I will keep an eye on it, and windows open at cold start to listen for the rattle

Richard Koop

Doing my tensioner today. Curious to see how my tensioner looks when I take it out.

Richard

artim808

Do you have photo of your tensioner? Did you noticed any difference after you replaced the tensioner?

Richard Koop

Just replaced it this past weekend and finished the job today. Here's a picture of the old one.




I'll let you know over the next couple of days if it fixed the issue.

Richard

artim808

Thanks Richard, keep us posted.

Richard Koop

And just to confirm my situation, after a cold start rattle and almost impossible to start issue I replaced the camshaft adjusters and that got things running again almost perfect. So my camshaft adjusters were bad. But I still sometimes had a minor cold start rattle issue and sometimes a P0016 code. So now to fix that I'm replacing the timing chain tensioner.

If that fails then eventually I'll replace the timing chain.

Richard

00Coupe

Did you just remove oil cap to see this? I checked mine, but it looks like a splash shield blocks you from seeing anything...

Richard Koop

I already replaced the camshaft adjusters. But still had a minor rattle at cold startup. Because my timing chain was still very taught I decided to replace the tensioner. My thought was that it wasn't holding oil after shutdown so it had gone bad. I never actually visually inspected the tensioner before I replaced it.

Not sure you can see the tensioner at all until you remove it from the car... if that's what you were asking.

Richard

00Coupe

In the very first post, there is a photo of chain and tensioner through some access hole.. My question is what is this access hole? I first thought you see this by removing oil cap, but it is not...

Richard Koop

Right. I definitely couldn't see the tensioner on my engine that way. I have an M271 engine in a 2012 C250 though.

Richard

mersum1es

It is oil filler hole. That applies only OM642, and there only earlier versions

Leon Pona

You mean the tensioner never fail ?

Leon Pona

you are right on ! , I suspect my tensioner , on my Sprinter , and not all the half of the engine ! Why Mercedes manual says chain is good for the engine life ?
But ,the tensioner never fail ? well. could be anything , right ?

Leon Pona

You mean the tensioner never fail ?

Leon Pona

you saying on 90.000 you should changed timing chain on MERCEDES BENZ ?

Leon Pona

This is not OM 642 right ? wha it is ?

Leon Pona

Oliver1232

I Replaced the one on the Right with the one on the left .

Fixed the starting noise and actually a lot of other chatter 5000 miles later still fine 2006 CDI 3.2 .... 200,000 miles total

peter2772000

You mean you replaced the one on the left with the one on the right. The one on the left is fully extended....