2004 E270CDi Drone/Buzzing noise

Page may contain affiliate links. Please see terms for details.

JohnnyW202

Active Member
Joined
May 22, 2011
Messages
146
Car
2004 Mercedes E270CDI Elegance Saloon, 2004 C200 Kompressor Estate Avantgarde SE Sport Pack
Good afternoon Gents,

I’ve just purchased yet another Benz my 7th overall (an expensive hobby)

It’s a lot nicer than my previous and much more expensive E320cdi oh how I hated that V6 and 7G box, most unreliable!

Anyway the latest acquisition is a late 2003 53 plate E270CDi elegance. Shockingly it has a cloth interior. Drives very well, looks well underneath.

I’ve had to do a few jobs such as rewiring the mirrors and disabling auto fold and a thermostat.

Only issue it had now is a buzzing/droning noise coming from rear of the vehicle sounds very similar to the noise I had from a cheap non oe back box on my W210 E220cdi but it’s a genuine Exhaust.

It goes away as soon as a little throttle is applied seems to be worst between 1,200-1,500rpm then disappears. Worse between 30-50mph particularly on deceleration/overruns, goes straight away with the least bit of throttle.

I’ve noticed the air filter box buzzes a little at idle and will need some new bushings but this loud drone comes from
the rear. I’m pretty sure it’s not the Valeo or Rumble strip issue.

Any help without throwing parts at it!
 
Do you think it sounds like exhaust resonance?
Definitely, was wondering if the double skin on the box had failed internally and was rattling around but I got under and gave them a good shake they seem solid.

Then I noticed there was a metallic rattle at idle barely noticeable, climbed under and what do you know the driver side mount has broken off the centre section of pipe just in front of the diff.

I’ll weld her up in the morning and report back, fingers crossed, it’s deafening at 25-30mph at light throttle or on the overrun.
 
Well I've changed the engine mounts and transmission mount. No vibration through the seats at idle now and no shudder on engine shutdown.

Welded up the broken exhaust mount and give the exhaust a good shake, seems solid.

However this deep drone is still there. My transmission, shifts smooth (better than my 203) and doesn't have any wandering revs or issues when climbing hills etc. As soon as it give it a little gas or back off it goes, it does sound like its coming from the rear though.

Any ideas, before I start replacing expensive radiators, putting aftermarket ATF coolers and changing fluid and TCs.
 
I wonder if its bearing related? Differential?
 
What was wrong with your E320 CDI? Please elaborate.

It was a remarkably strange model. A hybrid of the PFL and FL models.

It had the OM642 engine with 722.9 7G Gearbox.

Problems included:
-swirl flap motor failure due to the poor turbo seal, and linkages being so fragile it's almost impossible to replace in situ.
-A wiring loom that had been botched and subsequently worn through
-A turbo actuator that despite being replaced twice was still faulty until I got a brand new unit (These are not calibrated you simply match up the G number of the unit and replace)
- Turbine and Output shaft speed sensors needing to be replaced in the 722.9 box on the conductor plate (courtesy of ECUtesting in Derby)
- Rotten rear brake pipes leaking under protective plastic cover.
- Soft bushes on front control arms compressing under braking causing the car to shimmy badly (but no MOT advisories)

Anyway I just had a bad one but the OM642 is a poor engine to do maintenance on, when removing the turbo and EGR every bolt gave me issue due to the aluminium.
 
Anyone got any ideas. I've got a new Rad and Transmission Filter kit including pilot bushing on standby but this hum/drone has decreased with new engine mounts, if I bounce it on the throttle when it's doing it the frequency changes and it sounds like it's coming from the rear, bushes look good. I know the exhaust shields on these seem to wear through the mounting points, could be buzzing only at the right frequency. Wish I could stick a camera underneath at speed to see!
 
FWIW. My S211 E220 cdi has an exhaust resonance at roughly the same rpm range as you describe. It worsened at one point and my garage said the heat shield was rattling. They also found a fractured mounting bracket which they welded up. The car still has the resonance which irritates but I can live with. I suspect a loose baffle in the back box but externally the exhaust is fine. Maybe you have a noisier case of my issue?
 
Is it when driving you hear the noise?
 
It's not a rear wheel bearing by any chance?

I had a drone that would disappear under acceleration but was there at a constant speed. Initially did sounded like an exhaust issue to me.

The noise would also disappear on a twisty road on right hand bends but not left hand bends - that show I figured which side had the faulty bearing.
 

Users who are viewing this thread

Back
Top Bottom