2013 SLK350 Engine rattle on start

[xxaosicxx]

Hi all,

First post...so please be gentle

My 2013 SLK350 has developed a short-but-loud rattle on start up which happens about 50% of the time - sometimes after a drive and a short stop, sometimes on a cold start. It usually lasts between 2 and 5 seconds, but sometimes lasts longer and is sometimes much noisier. At one point it was rattling so hard the engine (and the car) was literally ROCKING side to side for about 5 seconds.

As the warranty on the car expires at the start of March I dropped it off at MB Whitefield on Wednesday. It's still with them now (they're also fixing a leaky roof seal under the warranty, which apparently will take them a week!), and - of course - they're saying they can't hear the sound I'm talking about.

I've done quite a bit of googling, and reading up on other forums, and have some ideas about what the problem might be - but I'd really appreciate some direct advice from you chaps.

Potential causes I've heard of so far:

• Secondary chain tensioners
• Non return valve in the oil filter housing being faulty allowing oil to drain away from the cylinder heads
• Knock caused by lifters leaking down

I do not claim to fully understand what each of the above means - but I really need my engine to not die on my out of warranty, so anything I can do to help the dealership determine the cause of the (apparently non-existent) problem would be great.

I've done a couple of videos, with sound, in case that would be any use to you all (I gave the same videos to MB).

Video 1

Video 2

All and any advice is greatly appreciated.

Thanks fellas.

Ben

 

[st13phil]

Hi Ben, and welcome.

It's always difficult to try to diagnose engine noises remotely, but if you're talking about the rattle / thrash noise immediately after start up on the video clips then may be the secondary timing chains rattling, but it's not particularly pronounced on your clips. For more info see my thread here, which includes a YouTube clip of an affected M157 V8. However...

...but sometimes lasts longer and is sometimes much noisier. At one point it was rattling so hard the engine (and the car) was literally ROCKING side to side for about 5 seconds.

This sounds much more like a fuelling / ignition problem as the secondary timing chains running under tensioned wouldn't cause that sort of effect.

I understand the dealer's difficulty in that if they don't hear the noise they can't diagnose it, so keep going back to them until they do hear it and please let us know what the outcome is.

 

[xxaosicxx]

Thanks for the reply - and for the link.

A lot of digging online last night (some on this forum) turned up what might be the cause of the problem - crankshaft bearings. From elsewhere on this forum:

The dealer keep it for a day and they acknowledge the noise and quickly told me, as other posters has mentioned, that this is a major repair that requires disassembling the engine as it's a crankshaft bearing problem. I'm a bit nervous since not sure how this will affect engine life as warranty is expiring in a few months. Once I pickup the car will post most info about the repair. Hope this helps

I told the dealer about it at every service but it couldn't be reproduced. Last service last month was shortly before my CPO warranty would expire, so I wanted this to be sorted out, even if I would only get some official statement this was normal. Noise finally could be reproduced this time. Dealer replaced timing chain tensioner on warranty but that didn't solve the problem. They didn't*find any standard issue on their computer.*

Because of a hint in this thread I recorded the noise on my phone and asked the dealer to send it directly to the factory (they have that possibility). Two days later I received an answer. Main bearings would be replaced on warranty.

Car was in surgery for about 1.5 weeks, just got it back today. Noise seems to be gone, engine starts much smoother in general.

If the dealership doesn't hear the sound for themselves over this week, I'll make the same request and see if I get a similar result. I'll keep you all informed as and when this progresses - though I am expecting some resistance from the dealership

 

[st13phil]

A lot of digging online last night (some on this forum) turned up what might be the cause of the problem - crankshaft bearings.

The quote you posted was (I believe) from the BenzWorld forum thread entitled "HELP: C300 engine noise on start-up".

If that's the case then it's about a different engine, the M272 while yours is an M276. Also, the noise from faulty crankshaft bearings tends to be a heavy, deep, knock or a deep rumble which I didn't hear on your clips?

 

[xxaosicxx]

That's good to know - thank you. I appreciate the input. This has been doing my head in for months...to the point where it's getting quite embarrassing when it's at it's worst. My 2012 SLK 250 CDI wasn't as noisy as this, and that sounded like a bloody tractor!

 

[Deleted member 65149]

There's some info on this in the thread entitled: M157 & M276 Camchain Tensioner - Heads Up My C350 with the M276 engine also rattles a bit on start up, but nowhere near as bad as yours sounds in the videos. Although of course without a reference sound level it's difficult to know from the videos exactly how bad it is. But yours does seem to have two different noises, the quieter ticking noise being more like mine. The louder and lower frequency growling on yours does sound bad. As you have identified, the cam chain tensioner may be the problem. Indeed there has been a MB notice issued on this http://mbworld.org/forums/attachmen...se-help-rattling-noise-after-engine-start.pdf. I've asked my dealer to check this out at each of the car's three services, but each time they've told me it's not an issue. I admit that it's not very loud and it seems to be getting less noticeable, but that may be just me getting "diesel-owner's ear" and no longer hearing nasty noises! It's a difficult one when the "experts" say that there's nothing wrong! How many miles has yours done? Mine has only covered 16k and I hope it doesn't get worse.

 

[xxaosicxx]

Wow..thanks for the PDF - that's really quite useful. Will take it to the dealership when I go to collect my car later in the week (assuming they get the roof back on!)

Mine has done about 22k on it so far...so fairly average mileage for a march 13 plate.

 

[xxaosicxx]

Alright then....so, an update. Today I collected my SLK350 from the dealership who has had it for the last 2 1/2 weeks.

I provided them with the Xentry report (thanks for that) and they performed the work FOC under my warranty.

Took it for a bit of a drive when I got it and then let it sit for a few hours before starting the engine again. The engine definitely isn't making quite the same noise as before - so I THINK it's an improvement...but then I could just be wishing it to be fixed so much that I'm imagining it!

I guess only time will tell....

New video here: https://www.dropbox.com/s/0webrfv2go88w6m/WP_20160125_14_50_29_Pro.mp4?dl=0

Thanks for your help guys,

Ben

 

[Deleted member 65149]

Good to hear you got it sorted - in your head at least! I know what you mean about wanting to convince yourself it's OK now. I only hear mine when I start it while the bonnet is up; half the time I think it's rattling and half the time I'm sure it's quiet. I can't help thinking I'm listening for something that's not there. Nobody else can ever hear anything wrong - must be all those noisy diesels that have ruined everyone's hearing

 

[xxaosicxx]

Time will tell I suppose!

The chap at MB informs me that this engine uses the fuel injectors from the diesel model - and that's why they do make a fair bit more noise on startup than we'd like. His words were "these V6 engines don't sound like the old ones did any more".

 

[xxaosicxx]

Final update... one week on, the engine has stayed the same...a bit noisier than I'd like, but certainly not doing the clattering, rattling sounds-like-a-transit-van sound it was doing before.

Anyone else with this engine experiencing the same should definitely present the Xentry document to their dealership and ask them to perform the work detailed within.

And, finally, a rare credit to the MB of Whitefield - and Chris Morley, the Service Manager - who got the technical guys to perform the repair based on the above document and my video clips alone, having never personally heard the noise for themselves.