Mercedes-Benz E 320 CDI

The Bosch high-pressure pump can cause rail pressure drop at high mileage. Difficult starting and erratic injection behaviour follow.

Symptoms: Hard starting (especially cold), engine only starts after several attempts, hesitation under load

The OM648 uses Bosch high-pressure injectors that tend to leak at high mileages. A faulty injector leads to poor combustion and increased soot production.

Symptoms: Rough idle, black smoke, power loss, frequent DPF regeneration, rising oil level

The OM648 turbocharger suffers bearing damage from insufficient oil supply or contaminated oil. Faulty oil return lines and blocked oil drillings contribute to the damage.

Symptoms: Whistling or rattling from the turbo area, blue smoke under acceleration, oil loss at the turbo

The crankshaft torsional vibration damper (harmonic balancer) disintegrates. Can cause severe engine damage if not replaced in time.

Symptoms: Vibrations at certain rpm ranges, knocking noise from the front, belt thrown off

Injectors develop leaks at the sealing seat. Two injector generations (with/without IMA coding) create confusion. Wrong types cause injection quantity problems.

Symptoms: Hissing at the injector head, oil film on injector bolts, rough running, elevated quantity correction values

The OM648 tends to timing chain rattle after cold start at higher mileages. Initially audible for only a few seconds, later persistent.

Symptoms: Metallic rattle after cold start (30–60 seconds), rpm-dependent rattling at 1,500–2,500 rpm

The OM648 oil cooler gaskets harden with age and develop leaks. The gasket itself is inexpensive, but replacement requires removal of the intercooler and coolant lines.

Symptoms: Oil drops bottom-right of the engine, oil smell after driving, dropping oil level with no other leaks visible

The OM648 dual-mass flywheel wears at high mileages. Repair usually includes the clutch as well and is carried out as a complete package.

Symptoms: Rattling and knocking when changing gear, vibrations at idle especially on shut-down, metallic noises

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.