My Wife's car also had a rattle at idle / low rpm's - expecially when cold - but later occured at temp also. thanks to a post by white rabbit - it was determined to be faulty mannifolds (broken welds). new manifolds were ordered from germany and the problem was cured under warranty.

here was the previous post:

http://www.slkworld.com/slk-r172-general-discussion/29647-two-week-oil-change.html

 

I have the same problem. Most prominent at about 1200 RPM. Not really related to whether the engine is cold or not. I recently took it in for service and they are ordering a new catalytic converter. I told them about the exhaust manifold problem but they are convinced it is the cat. I wonder if I will be able to say "I told you so." We'll see.

 

I believe that except for one person where replacing the cats worked, the fix for the exhaust rattle has been replacing the exhaust manifold(s).

 

I probably should have mentioned it - they also replaced the catalytic converter on my wife's car as well as the manifolds.

 

I am amazed that MB can make a car that costs a lot of money and seems to have so many problems. That seem common to them all

 

Finally got into the dealer, They thing replacing the C converter will solve the problem...stay tuned!

 

Finally got into the dealer, They thing replacing the C converter will solve the problem...stay tuned!

Been there done that and then they had to replace the exhaust manifold anyway.

 

I think I have this too seemed kind of funny today and when I rev to 4000 revs I'm getting a bit of vibration and pops come bangs, its doesn't do it all the time but most of the time.

 

Sounds to me like MB have some serious issues with the 172. I bet they dont do a recall though as its not a safety issue. Bit like the 171 oil consumption issue. They are happy to let owners pick up the tab

 

I think sometimes with a new model things get missed and production issues will only show themselves when the cars are used in the wild. It shouldn't happen but it doesn't surprise me - witness the current uproar with cloning BMW keys through the diag port.

I'm a little bit unhappy but as long as they fix it without messing around then I'll be happy again. Its the possibility of shirking responsibility and the inconvenience that bothers me the most.



edit:

If I get chance tomorrow I'll see if I can record how it sounds.

 

I am the worlds worst customer if I dont get value for money or any retailer or manufacturer tries to duck their responsibilities or fob me off. I advise anyone in the UK to pay by credit card any item that costs over £100 up to £30,000 even if its only the deposit. Your then covered my the Consumer Credit Act which makes the bank equally liable for any faulty goods. This of course wouldnt apply to a new 172 as they exceed the limit but it certainly applies to a used model

 

They changed the cats this week, still getthe popping noise when it fires up....is that the result of bad manifolds?

 

Just got my SLK back after a week in the shop. Both cats replaced and the left manifold had to be replaced as well.

 

so is this now our 1st known issue with the 2012? does the crayon smell count?

 

This is OLD thread I know, BUT it does relate 100% with my current issue.

My car is in the MB dealership for repairs. Same rattle noise from under the car somewhere, and happens especially upon start up and/or idling. When I first noticed it about 1 year ago, the dealer replaced the two cat converters under MB CPO warranty... A year later, the same noise... took it back in (now no longer under MB warranty) and I just got a text from my dealer which says as follows:

"Good morning... we ordered the parts for your car... I will update you tomorrow, Steve"

Well, I am assuming since they didn't call me about an estimate of repairs, this is likely same repair of the cat converters they are replacing, again, hence I won't be paying for it. What are the odds that it may be the manifold rather than the cat converters? Also, bcos I have an AM exhaust, they originally balked at the first repairs last year, but got convinced by my Indy shop repair guy that it was an MB unit at fault, hence they replaced the 2 cats.... Wonder if I should mention to them about the manifold.... don't want to have to pay for any repairs if I can avoid it...

Guess I'll find out soon enough if the actual problem is the manifold and not the cats... as reported here.

 

According to the service report, the diagnostic identified the left side cat converter as defective and source of the rattle, part was ordered, defective unit replaced, car tested (driven) by service tech and found to no longer have any rattle noise. Received a text message that my car was ready for pickup. Picked it up tonight and I am a happy camper again... for many reasons, that MB would fix my car while out of warranty... That is pretty nice. Didn't have to argue, didn't have to haggle, didn't have to negotiate anything... Took it in, they checked it out and replaced the defective part. This dealership has my undying support.

Drove it home, no rattle... and actually car seemed to have some zing while on the freeway.... Hoping that this puts the rattle issue to bed, for good... Now on to fixing the little issues of 3 bent rims...