Hi Every one
Has any come across this noise ?engine hot-between 1000 - 1500 rpm and under light load it make an awful metalic rattle,out side these conditions not a sound ? cars drives fine. One garage said they had heard it before does no harm leave it alone!!!,but i don't like all the noise as people hear you coming. anyone know what it is or how to fix it ? many thanks

 

manual transmission?

 

It all depends on the noise!
Could be a catalyst but this usually occurs when cold / idle.
Does it make the noise when the vehicle is stationary at 1000/1500?

 

Hi It's the owner-thanks for your reply's-I have done some investigation and found it's resonance of the block in relation to number 1 cylinder and merc know all about it and cover it up ! also heard some cars were bought back by merc as there is no fix to the noise-lemon law ? anyone have info ?
many thanks

 

Direct Injection (DI) is inherently prone to this noise. It's a function of combustion and the ongoing need to make cylinder block thinner (lighter) to further improve fuel consumption.
At the extremes of the parameters some customers begin to pick up the noise / complain.

Mercedes manage to reduce this noise more than most. Just try a few other diesels. Have you checked to ensure that all the underbonner sound insulation remains intact. Bonnet pad, undershield etc.

Once you notice the noise and get sensitive to it / know how to get it to make the noise (light / balanced throttle), it becomes very annoying but there isn't really anything wrong.

As engine components and fueling equipment wears this can make the problem worse since combustion is no longer as optimal as it was when new.

Keep the windows shut and turn up the radio.

That's why I stick with Petrol.

Stuart