Mercedes-Benz GLC X254

Development of the OM654 with 48V mild hybrid and integrated starter-generator. Clean and economical. Too new on the market for known weaknesses to have emerged.

• !! Coolant Pump Recall — Fire Hazard

  Recall action code 2090008: the electric coolant pump can develop an internal leak. Coolant enters the vacuum circuit and increases fire risk. Mercedes replaces the solenoid valve and applies a software update.

  Symptoms: Coolant loss without visible external leak, warning message on instrument cluster, in the worst case smoke development
  0–0 $
  Ad coolant pump recall OM654MA6542003001 coolant pump
• !! Tandem Oil Pump Failure from 80,000 km

  The OM654M combines the vacuum pump and oil pump in a tandem unit. If coolant enters the pump via the vacuum circuit the oil supply can fail. Replacement requires gearbox removal.

  Symptoms: Oil pressure warning, engine noises from oil starvation, in the worst case engine failure without prior warning
  2,000–5,000 $
  Ad Tandem-oil pump OM654MA6541800101 oil pump OM654M
• !! Potential Rocker Arm Wear from 100,000 km

  As an updated OM654 variant the OM654M carries the rocker arm/camshaft wear risk of the base OM654. Whether the revision fully resolves the issue remains to be seen.

  Symptoms: Ticking noise from valve cover area, misfires, engine warning light
  2,000–5,000 $
  Ad rocker arm OM654Mrocker arm OM654 Dieselcamshaft OM654M

+ 2 more engine weaknesses + vehicle weaknesses

Development of the OM654 with 48V mild hybrid and integrated starter-generator. Clean and economical. Too new on the market for known weaknesses to have emerged.

• !! Coolant Pump Recall — Fire Hazard

  Recall action code 2090008: the electric coolant pump can develop an internal leak. Coolant enters the vacuum circuit and increases fire risk. Mercedes replaces the solenoid valve and applies a software update.

  Symptoms: Coolant loss without visible external leak, warning message on instrument cluster, in the worst case smoke development
  0–0 $
  Ad coolant pump recall OM654MA6542003001 coolant pump
• !! Tandem Oil Pump Failure from 80,000 km

  The OM654M combines the vacuum pump and oil pump in a tandem unit. If coolant enters the pump via the vacuum circuit the oil supply can fail. Replacement requires gearbox removal.

  Symptoms: Oil pressure warning, engine noises from oil starvation, in the worst case engine failure without prior warning
  2,000–5,000 $
  Ad Tandem-oil pump OM654MA6541800101 oil pump OM654M
• !! Potential Rocker Arm Wear from 100,000 km

  As an updated OM654 variant the OM654M carries the rocker arm/camshaft wear risk of the base OM654. Whether the revision fully resolves the issue remains to be seen.

  Symptoms: Ticking noise from valve cover area, misfires, engine warning light
  2,000–5,000 $
  Ad rocker arm OM654Mrocker arm OM654 Dieselcamshaft OM654M

+ 2 more engine weaknesses + vehicle weaknesses

Completely new aluminium diesel with NANOSLIDE coating and integrated particulate filter. Noticeably quieter and cleaner than the OM651. Few typical faults known to date.

• !! Rocker Arm and Camshaft Wear from 80,000 km

  Known weak point: the narrow camshaft lobes and rocker arms in the OM654 wear prematurely due to inadequate lubrication. Mercedes issued TSBs.

  Symptoms: Ticking or knocking from engine bay, misfires, rough running, engine warning light
  2,000–5,000 $
  Ad OM654 rocker armOM654 camshaft VerschleißMercedes OM654 valvetrieb
• !! Electric Coolant Pump Leaking — Recall

  Over 800,000 Mercedes diesel vehicles with OM654/OM656 were recalled due to a leaking electric coolant pump. Coolant loss can lead to overheating.

  Symptoms: Coolant loss, overheating warning, coolant warning light, engine temperature rises
  0–500 $
  Ad OM654 coolant pumpcoolant pump OM654 recallA0005001400
• !! NOx Sensor Defective — AdBlue Fault and Start Inhibit from 90,000 km

  NOx sensors wear out from soot particles and deliver erroneous readings. Consequence: incorrect AdBlue injection, CEL illumination; if unaddressed, an engine start inhibit may follow. Both sensors can be affected.

  Symptoms: CEL, AdBlue warning, fault code P20EE or P204F, message 'No start after X km', rough idle
  500–2,000 $
  Ad NOx sensor A0009050108NOx sensor A0009050208Lambda sensor SCR Mercedes OM654

+ 8 more engine weaknesses + vehicle weaknesses

Development of the OM654 with 48V mild hybrid and integrated starter-generator. Clean and economical. Too new on the market for known weaknesses to have emerged.

• !! Coolant Pump Recall — Fire Hazard

  Recall action code 2090008: the electric coolant pump can develop an internal leak. Coolant enters the vacuum circuit and increases fire risk. Mercedes replaces the solenoid valve and applies a software update.

  Symptoms: Coolant loss without visible external leak, warning message on instrument cluster, in the worst case smoke development
  0–0 $
  Ad coolant pump recall OM654MA6542003001 coolant pump
• !! Tandem Oil Pump Failure from 80,000 km

  The OM654M combines the vacuum pump and oil pump in a tandem unit. If coolant enters the pump via the vacuum circuit the oil supply can fail. Replacement requires gearbox removal.

  Symptoms: Oil pressure warning, engine noises from oil starvation, in the worst case engine failure without prior warning
  2,000–5,000 $
  Ad Tandem-oil pump OM654MA6541800101 oil pump OM654M
• !! Potential Rocker Arm Wear from 100,000 km

  As an updated OM654 variant the OM654M carries the rocker arm/camshaft wear risk of the base OM654. Whether the revision fully resolves the issue remains to be seen.

  Symptoms: Ticking noise from valve cover area, misfires, engine warning light
  2,000–5,000 $
  Ad rocker arm OM654Mrocker arm OM654 Dieselcamshaft OM654M

+ 2 more engine weaknesses + vehicle weaknesses

The M139 is the logical development of the M133 and surpasses it in every respect: more power, better thermal management through an improved cooling concept, combined direct and port injection to fight intake valve carbon build-up. As a young engine with limited long-term data it is considered robust so far. Isolated reports of coolant sensor issues and water pump failures at high speeds. Tuning potential is enormous, but fuel supply must be upgraded at higher power levels.

• !! Turbocharger Stress Under Extreme Use from 100,000 km

  The world's most powerful series-production four-cylinder at 421 hp subjects its turbocharger to extreme stress. Without adequate cool-down periods after full-load operation, premature bearing wear is likely.

  Symptoms: Whistling at high load, oil mist in intake tract, power drop in heat
  2,500–5,000 $
  Ad Turbocharger M139Turbocharger M139 AMGTurbo M139 replacement
• !! Turbocharger Shaft Seal Leaking from 80,000 km

  The high-performance turbocharger on the M139 can push oil into the intake tract due to excessive shaft play. Early vehicles were subject to a recall for turbocharger bearing defects.

  Symptoms: Oil consumption without visible leaks, smoke cloud on cold start, power drop under high load
  2,000–5,000 $
  Ad Turbocharger M139BorgWarner turbocharger M139Turbo M139 BorgWarner
• !! Overheating After Spirited Driving from 60,000 km

  The M139 cooling system is designed at its limits. After extended high-load phases coolant temperature can reach critical values, especially in warm weather.

  Symptoms: Coolant temperature warning after spirited driving, restricted engine power through thermal management
  800–2,500 $
  Ad Water pump M139Cooling M139 AMGA1332001900 thermostat M139

+ 3 more engine weaknesses + vehicle weaknesses

Two-litre turbo with 350 kW, electrically assisted exhaust turbocharger, 150 kW electric motor on the rear axle — 500 kW system output. Barely audible at idle, often running on electricity alone. At full throttle a hoarse four-cylinder howl that doesn't satisfy the ears no matter how fast the needle rises. The electric turbo eliminates every trace of turbo lag; boost is immediate. 6.1 kWh battery in immersion cooling (14 litres of coolant flow directly through the cells). On paper a masterpiece: 2,165 kg in 3.4 seconds to 100, 280 km/h top speed. In practice a dilemma — the target audience wanted V8 sound and emotion, got 2.1 tonnes of high-voltage complexity. AMG chief Schiebe publicly admitted: customers were lost. Consequence: the CLE 63 gets a V8 back, the C63 successor will be the C53 with an inline-six. Maintenance is AMG-level: oil every 10,000 km (MB229.51, 7 litres), HV system only in certified workshops.

• !! Recall Gearbox Wiring — Harness Too Short

  Affected MY 2022–2023 AMG C43: incorrectly-length gearbox wiring harness fitted, can cause loss of drive.

  Symptoms: Warning in instrument cluster, sudden loss of drive, possible short circuit.
  0–0 $
• !! Recall Main Fuse Box — 80A Fuse Defective

  MY 2023–2024: Incorrectly manufactured 80A fuses in the main fuse box can fail and cause total electrical system failure. Free replacement at the dealer.

  Symptoms: Sporadic electrical failures, warnings in instrument cluster, in extreme cases complete electronics failure
  0–0 $
  Ad Fuse box W206 AMG80A fuse Mercedes C-classMain fuse box W206
• !! Recall HV Starter Generator — Software Fault

  Software fault in the high-voltage starter-generator control unit can cause loss of drive. Affects several AMG E Performance models. Free software update at the dealer.

  Symptoms: Sudden loss of drive, hybrid drivetrain warning, vehicle unable to pull away
  0–0 $
  Ad Starter generator W206 AMGRSG control unit Mercedes AMGHV starter generator software update

+ 9 more engine weaknesses + vehicle weaknesses

Current four-cylinder turbo with 48V mild hybrid and integrated starter-generator (ISG). Higher output than predecessor at lower consumption. Also used as PHEV base (CLE 300e).

• !! Oil Consumption from Piston Rings (Early Production) from 50,000 km

  Early M254 production batches 2021–2023 show elevated oil consumption due to insufficient piston ring sealing. Mercedes repair involves engine reconditioning.

  Symptoms: Dropping oil level between services, bluish smoke on cold start, consumption above 0.5 L/1,000 km
  2,500–6,000 $
  Ad Piston rings M254Oil consumption M254Piston ring set M254
• !! Timing Chain — Rattle and Premature Wear from 120,000 km

  The M254 exhibits timing chain rattle at cold start when oil change intervals are missed. Chain tensioner sealing rings can leak and lose tension. Engine damage is possible.

  Symptoms: Rattling or clattering from the engine bay at cold start, disappears after warm-up, worsens with extended service intervals
  1,500–4,500 $
  Ad timing chain M254 W206 tauschenchain tensioner M254 O-ring sealcamshaftnkette C300 W206
• !! Exhaust Valves Defective — Cylinder Head Damage from 60,000 km

  Defective exhaust valves and guides in the M254 lead to misfires and cylinder head damage. Mercedes USA extended the warranty to 15 years/150,000 miles; no official recall in Germany.

  Symptoms: Sudden power loss, severe misfires, CEL flashing, rough engine, dangerous misfires at motorway speed
  5,500–13,000 $
  Ad cylinder head M254 C300 tauschenexhaust valvee M254 defektvalve guide M254 W206

+ 3 more engine weaknesses + vehicle weaknesses

Current four-cylinder turbo with 48V mild hybrid and integrated starter-generator (ISG). Higher output than predecessor at lower consumption. Also used as PHEV base (CLE 300e).

• !! Oil Consumption from Piston Rings (Early Production) from 50,000 km

  Early M254 production batches 2021–2023 show elevated oil consumption due to insufficient piston ring sealing. Mercedes repair involves engine reconditioning.

  Symptoms: Dropping oil level between services, bluish smoke on cold start, consumption above 0.5 L/1,000 km
  2,500–6,000 $
  Ad Piston rings M254Oil consumption M254Piston ring set M254
• !! Timing Chain — Rattle and Premature Wear from 120,000 km

  The M254 exhibits timing chain rattle at cold start when oil change intervals are missed. Chain tensioner sealing rings can leak and lose tension. Engine damage is possible.

  Symptoms: Rattling or clattering from the engine bay at cold start, disappears after warm-up, worsens with extended service intervals
  1,500–4,500 $
  Ad timing chain M254 W206 tauschenchain tensioner M254 O-ring sealcamshaftnkette C300 W206
• !! Exhaust Valves Defective — Cylinder Head Damage from 60,000 km

  Defective exhaust valves and guides in the M254 lead to misfires and cylinder head damage. Mercedes USA extended the warranty to 15 years/150,000 miles; no official recall in Germany.

  Symptoms: Sudden power loss, severe misfires, CEL flashing, rough engine, dangerous misfires at motorway speed
  5,500–13,000 $
  Ad cylinder head M254 C300 tauschenexhaust valvee M254 defektvalve guide M254 W206

+ 3 more engine weaknesses + vehicle weaknesses

Current four-cylinder turbo with 48V mild hybrid and integrated starter-generator (ISG). Higher output than predecessor at lower consumption. Also used as PHEV base (CLE 300e).

• !! Oil Consumption from Piston Rings (Early Production) from 50,000 km

  Early M254 production batches 2021–2023 show elevated oil consumption due to insufficient piston ring sealing. Mercedes repair involves engine reconditioning.

  Symptoms: Dropping oil level between services, bluish smoke on cold start, consumption above 0.5 L/1,000 km
  2,500–6,000 $
  Ad Piston rings M254Oil consumption M254Piston ring set M254
• !! Timing Chain — Rattle and Premature Wear from 120,000 km

  The M254 exhibits timing chain rattle at cold start when oil change intervals are missed. Chain tensioner sealing rings can leak and lose tension. Engine damage is possible.

  Symptoms: Rattling or clattering from the engine bay at cold start, disappears after warm-up, worsens with extended service intervals
  1,500–4,500 $
  Ad timing chain M254 W206 tauschenchain tensioner M254 O-ring sealcamshaftnkette C300 W206
• !! Exhaust Valves Defective — Cylinder Head Damage from 60,000 km

  Defective exhaust valves and guides in the M254 lead to misfires and cylinder head damage. Mercedes USA extended the warranty to 15 years/150,000 miles; no official recall in Germany.

  Symptoms: Sudden power loss, severe misfires, CEL flashing, rough engine, dangerous misfires at motorway speed
  5,500–13,000 $
  Ad cylinder head M254 C300 tauschenexhaust valvee M254 defektvalve guide M254 W206

+ 3 more engine weaknesses + vehicle weaknesses

Current four-cylinder turbo with 48V mild hybrid and integrated starter-generator (ISG). Higher output than predecessor at lower consumption. Also used as PHEV base (CLE 300e).

• !! Oil Consumption from Piston Rings (Early Production) from 50,000 km

  Early M254 production batches 2021–2023 show elevated oil consumption due to insufficient piston ring sealing. Mercedes repair involves engine reconditioning.

  Symptoms: Dropping oil level between services, bluish smoke on cold start, consumption above 0.5 L/1,000 km
  2,500–6,000 $
  Ad Piston rings M254Oil consumption M254Piston ring set M254
• !! Timing Chain — Rattle and Premature Wear from 120,000 km

  The M254 exhibits timing chain rattle at cold start when oil change intervals are missed. Chain tensioner sealing rings can leak and lose tension. Engine damage is possible.

  Symptoms: Rattling or clattering from the engine bay at cold start, disappears after warm-up, worsens with extended service intervals
  1,500–4,500 $
  Ad timing chain M254 W206 tauschenchain tensioner M254 O-ring sealcamshaftnkette C300 W206
• !! Exhaust Valves Defective — Cylinder Head Damage from 60,000 km

  Defective exhaust valves and guides in the M254 lead to misfires and cylinder head damage. Mercedes USA extended the warranty to 15 years/150,000 miles; no official recall in Germany.

  Symptoms: Sudden power loss, severe misfires, CEL flashing, rough engine, dangerous misfires at motorway speed
  5,500–13,000 $
  Ad cylinder head M254 C300 tauschenexhaust valvee M254 defektvalve guide M254 W206

+ 3 more engine weaknesses + vehicle weaknesses

Current four-cylinder turbo with 48V mild hybrid and integrated starter-generator (ISG). Higher output than predecessor at lower consumption. Also used as PHEV base (CLE 300e).

• !! Oil Consumption from Piston Rings (Early Production) from 50,000 km

  Early M254 production batches 2021–2023 show elevated oil consumption due to insufficient piston ring sealing. Mercedes repair involves engine reconditioning.

  Symptoms: Dropping oil level between services, bluish smoke on cold start, consumption above 0.5 L/1,000 km
  2,500–6,000 $
  Ad Piston rings M254Oil consumption M254Piston ring set M254
• !! Timing Chain — Rattle and Premature Wear from 120,000 km

  The M254 exhibits timing chain rattle at cold start when oil change intervals are missed. Chain tensioner sealing rings can leak and lose tension. Engine damage is possible.

  Symptoms: Rattling or clattering from the engine bay at cold start, disappears after warm-up, worsens with extended service intervals
  1,500–4,500 $
  Ad timing chain M254 W206 tauschenchain tensioner M254 O-ring sealcamshaftnkette C300 W206
• !! Exhaust Valves Defective — Cylinder Head Damage from 60,000 km

  Defective exhaust valves and guides in the M254 lead to misfires and cylinder head damage. Mercedes USA extended the warranty to 15 years/150,000 miles; no official recall in Germany.

  Symptoms: Sudden power loss, severe misfires, CEL flashing, rough engine, dangerous misfires at motorway speed
  5,500–13,000 $
  Ad cylinder head M254 C300 tauschenexhaust valvee M254 defektvalve guide M254 W206

+ 3 more engine weaknesses + vehicle weaknesses

Current four-cylinder turbo with 48V mild hybrid and integrated starter-generator (ISG). Higher output than predecessor at lower consumption. Also used as PHEV base (CLE 300e).

• !! Oil Consumption from Piston Rings (Early Production) from 50,000 km

  Early M254 production batches 2021–2023 show elevated oil consumption due to insufficient piston ring sealing. Mercedes repair involves engine reconditioning.

  Symptoms: Dropping oil level between services, bluish smoke on cold start, consumption above 0.5 L/1,000 km
  2,500–6,000 $
  Ad Piston rings M254Oil consumption M254Piston ring set M254
• !! Timing Chain — Rattle and Premature Wear from 120,000 km

  The M254 exhibits timing chain rattle at cold start when oil change intervals are missed. Chain tensioner sealing rings can leak and lose tension. Engine damage is possible.

  Symptoms: Rattling or clattering from the engine bay at cold start, disappears after warm-up, worsens with extended service intervals
  1,500–4,500 $
  Ad timing chain M254 W206 tauschenchain tensioner M254 O-ring sealcamshaftnkette C300 W206
• !! Exhaust Valves Defective — Cylinder Head Damage from 60,000 km

  Defective exhaust valves and guides in the M254 lead to misfires and cylinder head damage. Mercedes USA extended the warranty to 15 years/150,000 miles; no official recall in Germany.

  Symptoms: Sudden power loss, severe misfires, CEL flashing, rough engine, dangerous misfires at motorway speed
  5,500–13,000 $
  Ad cylinder head M254 C300 tauschenexhaust valvee M254 defektvalve guide M254 W206

+ 3 more engine weaknesses + vehicle weaknesses