teksurv

So I have had my 2013 C350 for about three weeks now. The other day my buddy was walking over to the car just as I started it, after it had been sitting for about an hour, and he pointed out the knock knock knock that lasts about 2-3 seconds.

I am familiar with DI motors as my Audi had one as well. That is not the sound in question. I started searching and it seems there are quite a few people reporting perceived "engine knock" on warm starts. Funny thing is I have no noises at a cold start, only warm.

My question is, how many of you have this same issue?

Domm

Most likely it's the oil system pressurizing at start up. I found that the knock is not related to temperature, but more related to how long the car has been sitting.

H-ManZX

Hi,

the M272 engines had these problems with too large main bearings that took a couple seconds to build up oil pressure and in the meantime caused the knocking. Those bearings get replaced on warranty by MB.

But your '13 should have an M276 engine.

Anyway, google "C300 engine knock" and you'll find a thread in another forum with sound files included.

JaredP

I have the knock as well. brought it in for service because I was actually getting stalls on startup because of it. Apparently there is an engine software update for this specific issue on warm starts. The knocking is still there, but the technician didn't seem very concerned.

aznmode

I have this on my used 2010 like the car is misfiring. After about 30 seconds I hear a whining sound from the front for about 3 seconds, then the exhaust sounds normal after. I've just ignored it as others have mentioned they experience the same in another thread. Is there a long term side effect to this or it has to be fixed asap.

teksurv

When I go in for my 5k oil change I'll bring it up to the SA. I personally will not drive a car of this cost and history to have it sound this way.

Glyn M Ruck

The 90 degree V6 had a slight tendency to piston slap with ultra short skirt pistons until the oil film had built up. I have not listened closely to many 60 degree engines & they have some DI noise.

JaredP

Just got a call from my service department, a GLK with a M276 was just brought in with concerns about the engine knock. My SA let me know that an internal document was released on the 26th of June regarding the issue of an engine knocking sound for 2-3 seconds after the vehicle has been sitting for about an hour (Consistent with my problems, and others).

He said that the problem had to do with oil pressurizing or something of that nature, and said he had ordered parts necessary to fix the problem for the GLK. He will be in contact with me if the fix was a success, and how long it may take. I'll let you guys know, you may want to contact your SA.

teksurv

Good to hear, please reply back with the outcome.

VFORCE09

I have a 2013 c350 coupe with the same knocking issue at start up for about 2 to 3 seconds so when I took the issue to my service manager at Mercedes Benz of Cutler Bay in Miami he said that noise came from the timing tensioners so they were replaced with and updated version but that did not fix the problem so the service manager called the Mercedes tech line and was informed that they were comming out with and updated check valve (thats what they called it) i have no idea what this valve does but we will find out this Tuesday when there installing the new valve for this knock issue...

teksurv

I have an appointment to drop mine off this Friday at Mercedes-Benz of Escondido. I will post the outcome.

teksurv

My SA says the tech diagnosed my issue as the timing tensioners like the person above posted. They are ordered and we'll see what happens in a day or two.

JaredP

You should give them a call and see if they can find any documentation on the "check valve" replacement. I PM'd VFORCE09 and he said that the check valves fixed the issue, while the timing tensioner did not.

VFORCE09

OK here is my update:

on Friday I pickup my car and so far no start knock issues

but For some reason they changed the tensioners again but also added a new updated valve that was the main reason for the knock..problem solve for me

teksurv

Thanks for the update. Do you happen to have the part numbers on the invoice for what was replaced?

VFORCE09

not on me but as soon as I get home I'll post the numbers from the invoice

andrewpang3

Thanks! Can you scan your invoice and black out your info? It would help us with some credibility at MB.

MDMercedesGuy

The check valve makes a lot of sense. If the oil passages are completely dry, it can take a few seconds for oil to get everywhere and up to pressure.

teksurv

That would be awesome.

VFORCE09

here's the part numbers on the invoice for the knock noise

1. 2760502500
1. 2760502600
16. 000000006365
1. 003989982010
6. 2761410180
2. 2780504000
015702
057807
057806
015703

LI05.10-p-056435



sorry my scanner is not working right now

andrewpang3

Would you be able to take a photo of the work order? You would be a savior to all of us!

Thanks

VFORCE09

Ok guy's
Here is my mercedes invoice
hope this helps

andrewpang3

Thanks VFORCE09

Did you have the knocking on cold starts or when it sits for a bit after a drive?

The work order states cold starts. Just trying to clarify.

Thanks!

VFORCE09

when it sat for a while and the motor cooled down, like about 30 to 50 minutes

Glyn M Ruck

This is very interesting. Thanks for that!