W211 E270 Engine rattle at idle

[garyenelson]

Hi all,

My 2005 W211 E270 CDI has developed a strange "tinny" rattle at idle. It sounds a bit like a bit of exhaust heatshield vibrating. I've had the cats checked but apparently they are okay. Also had it up on a ramp but couldn't see any issues with heatshields either.

It is loudest down by the drivers side front wheel. The sound is beginning to drive me insane. It's got to the point where I'm too embarrassed to let the car idle anywhere.

Has anyone came across anything like this before? The car is driving perfectly and the noise stops as soon as you touch the accelerator.

 

[mersum1es]

check air filter housing. Often bolts loosen and/of rubber dampers missing.

IF sound is coming more middle of the car, exhaust pipe attachment might be broken.

 

[garyenelson]

Thanks for your reply.

I've already checked around the air filter but it's a different rattle to that. It's more of a metallic tinny rattle. Can't see anything wrong with exhaust or mounts.

It's driving me insane trying to find it!

 

[alecmascot]

My money is on the alternator pulley clutch ?

 

[mersum1es]

My money is on the alternator pulley clutch ?

Good point, if belt is flappin too, this is very likely culprit.

Then again, try 'mechanic stetoscope' and listen if sound source is injectors. Wrong pre injection cause also extra sound, though it is more like diesel knocking, and often cause uneven idle

 

[garyenelson]

Thanks for the suggestions.

I managed to get this sorted this afternoon. Put the car back up on the ramp again with the engine running and traced it to a bit of heat shield at the side of the gearbox!

Bent it back a bit and all is quiet again

 

[trapperjohn]

And lovely result, I can hear your wallet heaving a sigh of relief from here.