Mercedes-Benz GLC 300 Coupé
Modern turbocharged four-cylinder with direct injection and piezo injectors. Successor to the M271. Less susceptible to timing chain issues. Good balance of power and economy.
Coupé Sense
180 kW in the SUV coupé — the sporting shape promises more than the engine delivers.
Engine Weaknesses 6
The high-pressure fuel pump on the M274 is driven by a lobe on the intake camshaft. Wear on the drive lobe or pump follower leads to pressure drop.
Symptoms: Metallic ticking from engine area, starting problems or extended cranking, power loss, fault code P0087
On the M274 too, the camshaft adjuster solenoids develop leaks. Oil penetrates the wiring harness by capillary action and can damage the engine ECU.
Symptoms: Fault code P0010, CEL, oil traces at camshaft connectors, lambda sensor failure, in severe cases ECU failure
Primary weak point of the M274: the electric thermostat sits deep in the engine block and is hard to reach. Replacement takes around 3 hours.
Symptoms: Engine does not reach operating temperature or overheats, temperature fluctuations, fault codes P0597–P0599
The PCV valve on the M274 clogs or breaks. Fault code P052E. Parts are inexpensive (~€63), but installed hidden under the engine ECU.
Symptoms: Fault code P052E, CEL, power loss, fault returns immediately after clearing
The M274 petrol engine has two NOx sensors that frequently fail. Each sensor costs around €600 as a part; with both sensors the repair bill quickly reaches €1,500.
Symptoms: Check engine light, NOx sensor fault code, elevated exhaust values, possible limp mode
The M274 with direct injection and no port injection tends to carbon deposits on intake valves like all GDI engines. Walnut blasting every 60,000–80,000 km is recommended.
Symptoms: Stumble under partial load, rough idle, slight power loss
Vehicle Weaknesses 11
Aluminium steering rack bolts corrode due to road salt. If all three bolts fracture, power steering fails completely. KBA recall 012425.
Panoramic roof can spontaneously shatter while driving, triggered by temperature differentials or pre-damaged surfaces. Glass shards inside the cabin. No systematic recall known.
Recall in late 2021 due to fire risk from possible fuel leak. Affects GLC models build years 2015–2020. Free repair by dealer.
The 9-speed automatic jerks when changing gear, particularly between low gears. Defective wiring harnesses can cause drive loss. A software update often helps.
Active brake assist, ESP and blind-spot monitor fail sporadically. Corroded wiring harnesses and control unit faults are the causes.
AMG models with large wheels tend to develop noises at the front axle when turning on wet roads. Ball joints and strut top mounts wear faster.
The rear brakes wear unusually quickly due to frequent ESP interventions. First warnings can appear as early as 35,000–40,000 km.
The Artico synthetic leather on GLC seats cracks on many vehicles after just 3–5 years. Replacement cost per seat is €500–800.
The Artico synthetic leather on seats and door cards cracks and flakes prematurely, particularly at the side bolsters.
Many GLC owners report persistent brake squeal that does not disappear even after pad replacement. AMG models with sports pads are frequently affected.
The standard Artico artificial leather shows cracks from approx. 40,000 km, particularly on the side bolsters and backrest of the driver's seat. Mercedes occasionally offers goodwill repair.
Reports & Tests
538 owner complaints filed with NHTSA (2015–2022). Most reported: Engine (158), Other (99), Electrical (79).