Could it be Big Ends?

[SoopDood]

Bought my 54 plate SLK 200 21k miles four weeks ago and am very pleased with it but for one concern I now have.

On a morning cold start, I've began to notice a 2-3 second low level rumble noise from the engine which then disappears, I guess due to the oil pressure building up. If the car is left 3-4 hours during the day its also noticeable on starting the engine again then.

From past experience, it sounds like big ends knock albeit not loud. However how can that be with a relatively new and low mileage Mercedes engine !

So question is, am I being paranoid and / or is this typical of these cars?

My neighbour is an ex Mercedes mechanic and he commented after listening to my car engine that he'd never heard that noise on a Merc before.

Roy

 

[Brian WH]

When was it last serviced? If the oil is old it may not be lubricating properly. At the least it could do with an oil change to see if that helps.

Do you not have any warranty with the car?

Moved to engine section.

 

[jaymanek]

Those engines do make noise on a cold start for a few minutes.. It alarms customers when i start them in the showroom...

IIRC its something to do with exhuast gasses & warm up..

 

[BlackC55]

Can you record the noise so we can here it?

 

[panason1c]

A low level 'rumble' is normally caused by worn crankshaft main bearings rather than big-end bearings which would cause a 'knocking' sound.

 

[Deleted member 6183]

Without wanting to sound patronising it more likely to be new owner syndrome.

We're all the same with a new car, looking for faults an determined to find one!

Our SLK makes a slight tapping noise for the 1st few seconds when cold, I've put it down to oil not yet circulated and I'm sure I read a thread where it's said to be common with these engines.

 

[BlackC55]

Without wanting to sound patronising it more likely to be new owner syndrome.

We're all the same with a new car, looking for faults an determined to find one!

Our SLK makes a slight tapping noise for the 1st few seconds when cold, I've put it down to oil not yet circulated and I'm sure I read a thread where it's said to be common with these engines.

the exhaust manifolds can leak too causing that ticking noise.

 

[Deleted member 6183]

the exhaust manifolds can leak too causing that ticking noise.

Cheers, another thing to worry about!

 

[jaymanek]

yes but if it goes away once warm, i wouldnt worry.

 

[Deleted member 6183]

yes but if it goes away once warm, i wouldnt worry.

Pretty much the way I feel about most things.

 

[big x]

My BMW makes a similar noise and it's the air pump.To warm the cat quicker it injects air into the exhaust manifold for 2 minutes to super-heat the combustion gases.

 

[BlackC55]

That year SLK has no air pump.

 

[SoopDood]

Thanks for all your comments and yes Lewyboy, you could be absolutely correct about me being in new owner paranoia syndrome. But knowing my luck, if I did nothing now and it got out of warranty, I'd most likely end up having a major engine problem. So no harm checking it out to be safe. Also, by getting this on record with MB now, and if a problem did occur with time, at least I have a bit of historical evidence to go back on.

My car is back to the main dealer today that I bought it from under its 1yr warranty. They plan to keep it for a few days to start it in the mornings and late afternoons. I have to say, they have been very understanding and helpful. It has also given me a chance to try out their newish CLK diesel courtesy car which is very nice....

When I asked if a 'slight' big end knock type noise was normal on these cars the service manager said he'd never heard of that before. so even more reason to get it checked.

I'll update you all later in the week once I get their feedback.

Roy

 

[SoopDood]

Car was in MB main dealer for four days this week. They started her each morning and late afternoon. Two service technicians had listened to it but no oil pressure check was done. The service manager subsequently said that my car engine is ok and that the big end type rattle noise is totally normal at start up.

Now I work in engineering and restore old cars as a hobby so I know a bit about cars and engines etc and I'm not convinced about this. So I plan to get an independant second opinion. It just doesn't sound right.

 

[BlackC55]

I suspect the dealer is correct but it is worth getting a second opinion.

 

[jaymanek]

Bognor is not a million miles from Horndean!!

Olly is your man on this one.

www.prestigecarservice.co.uk