Mercedes-Benz CLE C236

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

Return to the inline-six after years of the M276 V6 — and the difference is immediately noticeable. Smoother, more even rev build-up, torque plateau from 1,600–4,000 rpm without any weakness. The 48V mild-hybrid system with integrated starter-generator (ISG) is not a marketing term: 16 kW of boost on pull-away fills turbo lag completely; measurable fuel saving in sail mode. When buying, check the 48V battery — failure costs 2,000–4,000 EUR, primarily affecting build years up to 2022. Electric coolant pumps can fail from 80,000 km. Change oil every 10,000 km, do not rely on Longlife — HPFP and camshaft adjusters are sensitive to old oil. Cold-start wastegate bushing rattle is by design and not a fault. Overall a very accomplished engine that holds 250,000 km without issues when maintained correctly.

• !! 48V ISG Battery Failure from 70,000 km

  Frequently reported problem: 48V battery of the EQ Boost system fails and costs 2,000–4,000 EUR to replace. Design issue with earth connection in early vehicles.

  Symptoms: EQ Boost deactivated, start-stop system failed, hybrid warning light, sporadic starting problems
  2,000–4,000 $
  Ad 48V battery M256EQ Boost battery M256ISG battery M256
• !! Camshaft Adjuster Solenoid Leaking — Oil in Wiring Harness from 100,000 km

  The known Mercedes problem of leaking camshaft solenoids also affects the M256 (same solenoid technology as M276/M270). Oil migrates by capillary action and destroys lambda sensors and the ECU.

  Symptoms: Lambda sensor fault codes, MIL, rough running. Multiple electrical faults simultaneously as it progresses
  1,700–4,000 $
  Ad Oil stop cable M256 camshaft solenoidCamshaft solenoid E450 leakingWiring harness camshaft M256 oil
• !! Elevated Oil Consumption at Higher Mileage from 100,000 km

  M256 shows elevated oil consumption from approx. 100,000 km, attributable to the PCV system and cylinder walls. Regular oil level checks necessary.

  Symptoms: Dropping oil level, occasional bluish smoke after warm-up phase
  500–3,000 $
  Ad Oil consumption M256M256 3.0 turbo oil consumptionPiston rings M256

+ 6 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

Return to the inline-six after years of the M276 V6 — and the difference is immediately noticeable. Smoother, more even rev build-up, torque plateau from 1,600–4,000 rpm without any weakness. The 48V mild-hybrid system with integrated starter-generator (ISG) is not a marketing term: 16 kW of boost on pull-away fills turbo lag completely; measurable fuel saving in sail mode. When buying, check the 48V battery — failure costs 2,000–4,000 EUR, primarily affecting build years up to 2022. Electric coolant pumps can fail from 80,000 km. Change oil every 10,000 km, do not rely on Longlife — HPFP and camshaft adjusters are sensitive to old oil. Cold-start wastegate bushing rattle is by design and not a fault. Overall a very accomplished engine that holds 250,000 km without issues when maintained correctly.

• !! 48V ISG Battery Failure from 70,000 km

  Frequently reported problem: 48V battery of the EQ Boost system fails and costs 2,000–4,000 EUR to replace. Design issue with earth connection in early vehicles.

  Symptoms: EQ Boost deactivated, start-stop system failed, hybrid warning light, sporadic starting problems
  2,000–4,000 $
  Ad 48V battery M256EQ Boost battery M256ISG battery M256
• !! Camshaft Adjuster Solenoid Leaking — Oil in Wiring Harness from 100,000 km

  The known Mercedes problem of leaking camshaft solenoids also affects the M256 (same solenoid technology as M276/M270). Oil migrates by capillary action and destroys lambda sensors and the ECU.

  Symptoms: Lambda sensor fault codes, MIL, rough running. Multiple electrical faults simultaneously as it progresses
  1,700–4,000 $
  Ad Oil stop cable M256 camshaft solenoidCamshaft solenoid E450 leakingWiring harness camshaft M256 oil
• !! Elevated Oil Consumption at Higher Mileage from 100,000 km

  M256 shows elevated oil consumption from approx. 100,000 km, attributable to the PCV system and cylinder walls. Regular oil level checks necessary.

  Symptoms: Dropping oil level, occasional bluish smoke after warm-up phase
  500–3,000 $
  Ad Oil consumption M256M256 3.0 turbo oil consumptionPiston rings M256

+ 6 more engine weaknesses + vehicle weaknesses