Slack in timing chain keep re apearing after a few mins of running

[Pinder]

I have been noticing a clacking sound after the engine runs for a few mins. If i take the valve cover off there is slack in the chain by the timing chain guide. I can move it around and i am convinced this is the clacking noise.  If i pump the tensioner or turn the engine the slack goes away. The timing chain is new and so is the cam sprocket. It almost seems like the tensioner looses tension after running.  Do i need an new tensioner? Considering the price of a new one i want to be sure it is the tensioner. Any advice will be helpful.

[Benz Dr.]

Something wrong with your tensioner. They don't fail that often but if they do you won't always hear it. I suppose you could try taking it apart and cleaning it but I would look for a new one or a good used unit to replace yours.

[Pinder]

Thanks Benz Dr. I try cleanout first and if that does not work then. New one.

[ja17]

Yes the tensioner is fairly basic, but a little pricey to replace. I think you can still buy a kit from Mercedes with the inner moving parts (spring, cup, ball etc.) for a fraction of the price of a new tensioner.

[Pinder]

An update on the timing chain tensioner. I removed the piston , spring plastic cap and check ball and cleaned it. I did a quick check to see if the check ball holds pressure or at least seals the piston end by inserting rhe spring into the piston with cap and ball bearing in place. With spring pushed in hard i could blow air through the other end. To me this meant that the cap bottoms out before the ball bearing seals the hole. I corrected this by slightly sand papering the cap end. This allowed the ball bearing to sit slightly higher in the cap. I re installed the parts and was able to pump up the tensioner. So maybe this may help someone do a simple repair.

However i still get a clacking noise after letting the car run a few mins.  The noise seems to come and go and can be made to come back after reviing a bit few few seconds. It seems to disappear sometimes. Any hints would be helpful.