W245 Knocking on start up (Video)

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Neight

New Member
Joined
Sep 18, 2017
Messages
4
Location
essex
Car
2011 B160 Sport
Hello all, I have had a look through the forum to find an answer to this, but had no joy so far. So I thought I would put it out there to you guys. I have had my 2011 B160 Sport (35k, full MB history) for about four months now and recently have picked up on a knocking/rattle sound on start up which disappears when pulling away and idling after. I have a couple of months left on the warranty, so if this is something big, I'm pretty keen to get it diagnosed.
It is relatively intermittent which doesn't help, but it sounded particularly bad the other morning, so I videoed it. When it was this loud, it was obviously coming from the drivers side, where the belt is.
Could I ask you have a look and maybe share your thoughts? I really appreciate your help if possible.

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That imo sounds serious enough to stop driving it immediately and return it under guarantee ...................

Sounds heavy and crankshaft rotation speed related ................ big end bearing?
 
That was my initial thought when I first heard it. Although it disappears as soon as the revs come up. It also runs perfectly apart from this and some days the noise is absent. My very limited knowledge led me to hope it wasn't as bad as that?.
 
One possibility is a noisy alternator overrun pulley but could equally be a timing gear/chain problem.
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I would go speak to a dealer with the video evidence in hand - no way they should tell you to go away and that its normal
 
Thank you for your replies gentlemen.
I'm going to double check the warranty details and then get on to the trader, see what he has to say!

Anyone got any tips on how to play it? Can't imagine it will go well.
 
Be firm but fair in your approach. The fact your car has a problem on start up should not be a subject for discussion- what should be discussed is what the seller of the car is prepared to do about it. Quite often these warranties supplied by dealers are in the form of a third part insurance they have bought/supplied as part of the deal. If that's the case ideally you want the dealer on your side by acknowledging the problem is real. Make sure they get that video evidence when you contact them.
 
Thanks Graeme, will let you know how it goes.
 

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