E240 Noise from transmission

[jimmy lee]

I have a 1999 E240 Avantgarde auto with 65000miles. It makes a slight knocking noise at low revs from what sounds like the differential area. It seems to sound worse once the car has warmed up. There is no loss of power or performance, in fact if you floor it from a standing start there is no noise at all. A friend of mine, who has owned meny a Mercedes, reckons that it might be the exhaust knocking on something.

Also when you floor the accelerator the engine does sound a bit on the noisy side. Is this normal? This is my first E240, my first Merc was an 1997 C180 which didn't sound at all noisy but it did have a smaller engine.

Any suggestions Mercedes owners?

 

[Dieselman]

Just check everything out. The differential won't normally knock but check the oil level anyway. A regular knocking sound could be the driveshaft CV joints.

 

[jimmy lee]

I should be able to get it up on a ramp this week. What should I be looking for?

 

[BlackC55]

Have a look at the prop coupling(s) on the propshaft for play. Its very unlikly that the drive shafts will be worn. Have a look at the diff hangers too and see if there is any play. This is too very unlikely but worth a look. Give the exhause a waggle and any excess movement should present itself.

 

[jaymanek]

Regarding the engine sound, what sort of noise do you mean? the v6 engines are very smooth normally...

 

[jimmy lee]

Regarding the engine sound, what sort of noise do you mean? the v6 engines are very smooth normally...

It,s very smooth and it sound like a V6 should. It's just that it's rather loud. Like there is not a lot of sound insulation between the engine bay and the interior. Is this normal.

 

[BlackC55]

Does it have all of its undertrays present?

 

[jimmy lee]

Everything seems present at a look underneath.

 

[DrNick]

Check the integrity of the rubber cover over the steering column UJ (where the steering column passes through the bulkhead. Mine split and this lets noise into the cabin. In my case it seemed to be coming in through the airvents, but it was down to this split cover.

Worth a look ( or a sock stuffed into the gaiter - accessed by pulling up the carpet around the steering column!)