2011 Ford C-MAX 1.6L Petrol · NB52 NXB

On seven-seat Grand C-MAX models, the twin sliding rear side doors rely on concealed lower roller carriages, centre hinge runners, and electronic latch actuators. In typical family use, road grit and moisture accumulate in the lower sill tracks, causing the plastic-coated roller bearings to seize and disintegrate. This leads to the heavy door dropping, jamming in its guide channel, and scraping the vehicle quarter panel paintwork. Concurrently, the internal door latch microswitches and child-safety solenoid mechanisms suffer electrical failure, triggering continuous false door ajar warnings or refusing to lock via the central locking system.

The 1.6-litre Duratorq TDCi diesel engine is vulnerable to combustion gas blow-by past the copper injector base washers. As the crush washers erode, unburnt diesel fuel and combustion carbon blow past the injector body, creating a hardened black tar deposit around the cylinder head known as the black death. Carbon contaminants eventually enter the engine oil gallery, creating sludge that blocks the banjo bolt micro-mesh oil feed filter to the turbocharger. Oil starvation causes rapid turbocharger bearing failure, turbine destruction, and catastrophic engine runaway if oil is ingested into the intake.

Both the dry-clutch DPS6 (6DCT250) fitted to 1.6 petrol models and the wet-clutch MPS6 (6DCT450) fitted to 2.0 TDCi diesel models suffer from transmission drivability faults and internal wear. On wet-clutch diesel units, neglecting the critical 3-year or 37,500-mile transmission fluid and filter change causes contaminated fluid to clog the mechatronic valve body solenoids and clutch packs. This produces severe low-speed judder, harsh gear shifts, sudden neutral drop-outs, and transmission malfunction warnings. On dry-clutch petrol models, clutch pack glazing and transmission control module (TCM) circuit failures are common.