Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
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Did the dealer change out the timing chain tensioner at all?
Let me know so we can continue,thanks Pete.
If you can send the video this will help.You may have to upload the video to You tube and send me the link to see if.They may have inspected the tensioner and it seemed fine but it does also operate off of oil pressure.If the oil pressure is leaking past this tensioner then it will cause this noise here on start up especially when cold.In some cases you can use an automotive stethescope and listen around the tensioner shown below to see if it loudest when this occurs to help determine if it needs replaced.
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I believe the only way to tell for sure is to remove it properly and then apply air pressure to the oil feed hole when it is cold to see if it pushes out or if you can hear or see air bleeding past it.I have checked several of these this way before.The pressure pin (1a) in the diagram should push out when air is forced in through the oil feed hole.
This does sound like the tensioner to me from here with what is described and I have seen these fail before.
The other issue is the oil pressure pump.This would need tested with an oil pressure test gauge attached to the engine and when started cold to see if oil pressure is low or non existent right away.
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I always try and change the tensioner when doing a timing chain if the customer will allow, as your already in there for one and like you said the part is cheap.I am not real sure why they did not even offer it to you unless they really thought it was o.k. but if they did not check the pressure side of it then it would be difficult to say it is o.k.
Your engine has hydraulic lash adjusters which are just like lifters and also fill with oil.These are also very common to bleed down oil pressure causing this fault here.Normally the noise is heard around the top or sides of the engine with this issue here.They look like this below ( #2).
Usually this fuse will short out when the compressor is either shorting out or drawing to many amps.This would be the air suspension compressor usually needing replaced as well as the compressor relay.This will cause the light you see to come on.
The adjuster can sound like a chain slap issue here as it does also work with oil pressure.With the oil cap loose this would have not caused a failure like this here.
Usually it isnt damaging but can become worse to where it may be there all of the time.