Mercedes-Benz A 170 CDI

The copper sealing ring between injector and cylinder head fails and allows combustion gases to escape. A tarry black sludge forms around the injectors. If ignored the injector will break on removal.

Symptoms: Diesel smell inside the vehicle, rough idle, black tar-like deposits on the engine block around the injectors, three-cylinder running

Corrosion and tar deposits can cause injectors to seize in the cylinder head. If an injector breaks during removal, extensive cylinder head work is required. Special tools and experience are essential.

Symptoms: Seized injectors discovered during workshop inspection — no driver indication beforehand, only apparent during repair

The K9K-based OM668 in the Citan is prone to premature timing chain stretch. Multiple cases of chain failure and total engine loss documented. Clicking on cold start is an early warning signal.

Symptoms: Clicking or rattling on cold start, noise from front of engine, CEL, in extreme cases engine stall

The Citan with OM668 is highly sensitive to short-distance use. Regeneration interval is only 1,000 km in urban operation. Trips under 15 km prevent regeneration — DPF clogs.

Symptoms: DPF warning light on, engine enters limp mode, increased fuel consumption, engine oil smells of fuel from post-injection

The Citan's DMF wears out sooner than expected in commercial use with frequent stop-and-go. Clutch judder and squeaking during gear changes are among the most frequently reported problems.

Symptoms: Judder on pull-away, squeaking or clicking during gear changes, vibrations at low RPM, uneven clutch pedal feel

Water collects between wheel arch liner and sill, keeping it permanently damp. Extensive through-rusting of side sills including structural damage. Older examples regularly severely affected.

Rear wheel arches rust extensively, sometimes with risk of perforation. Door sills and tailgate also frequently affected. Vehicles over approximately 8 years without regular care are severely at risk.

Suspension springs on front and rear axle break, leading to unstable handling. After a break, wheel alignment and adjustment are required.

Springs break frequently, especially in the upper coils. Affects the entire W168 range. Strut mounts wear and cause clicking when steering, particularly on older examples.

Door hinges rust from the inside out and can break, causing the door to sag and requiring lifting to close properly. Particularly on vehicles without regular underbody maintenance.