Mercedes-Benz E 220 CDI
Development of the OM611. Economical and reliable; known weakness is the crankshaft damper. Check belt tensioner.
Diesel Standard
125 kW diesel. Functional and economical, emotionless.
Engine Weaknesses 6
On the OM646, all 8mm rivets in the DMF can shear. The resulting imbalance damages the clutch disc and crankshaft position sensor. Repair approximately €2,000.
Symptoms: Clutch shudder when engaging after cold start, vibrations when pulling away, loud rattling or clattering at part load
OM646 injectors wear internally through deposits; elevated return quantities cause rough running and power loss. EGR coking aggravates the problem.
Symptoms: Hard starting (especially cold), hesitation under acceleration, rough idle, dark exhaust plume
The OM646 exists in variants with and without an alternator freewheel. Belt tensioners are not interchangeable. Workshops frequently confuse the two types.
Symptoms: Belt flutter at the alternator area, squealing noises, alternator damage, belt snap
The OM646 develops rattling noises from the timing chain at higher mileage. The duplex chain is robust but the tensioner and chain guides wear out. Less common than on the OM651.
Symptoms: Quiet rattling at idle especially after cold start, noise from the rear of the engine, disappears at higher revs
The EGR valve clogs with soot deposits, especially with short-trip driving. The valve sticks open or stays closed and triggers limp mode.
Symptoms: Power loss at low rpm, rough running, engine warning light, limp mode on cold start
At higher mileages the valve cover gasket and turbocharger flange gaskets leak. Oil drips onto hot engine components and causes smoke.
Symptoms: Oil smell inside or in the engine bay, oil film on the outside of the engine, smoke, dropping oil level
Vehicle Weaknesses 7
Sensotronic Brake Control on pre-facelift models (2002–2006) suffered hydraulic failure. Approximately 1.3 million vehicles were recalled worldwide. Repair cost €2,200–3,500.
Airmatic air suspension fails due to compressor failure and defective air reservoirs. Replacement is only possible with the rear axle removed.
The Signal Acquisition and Actuation Module (SAM) fails, particularly when water ingress occurs. Leads to loss of lighting, windscreen wipers and instrument cluster.
SBC electrohydraulic brake (2002–2006) suffered from faulty high-pressure pump control. Two recalls in 2004 and 2005. SBC vehicles require specialist workshop.
AIRMATIC air suspension wears heavily. Air reservoir and compressor fail frequently. Replacement requires complete rear axle disassembly — very costly.
Control arm and track rod end bearings develop play. A common MOT failure point. Regular cause for failed MOT inspection.
SAM modules (front and rear) control lighting, wipers and door functions. Moisture damage and ageing lead to complete failures.