Mercedes-Benz B-Klasse W246

Renault-based small diesel (K9K). Economical but with little power reserve. Prone to EGR fouling and DPF issues under pure short-trip use.

• !! Timing belt instead of chain -- maintenance obligation from 120,000 km

  The Renault K9K-based OM607 uses a timing belt that must be replaced every 120,000 km or 6 years. Neglecting the change leads to snapping and severe engine damage.

  Symptoms: No noticeable warning before snap -- sudden failure with no advance notice if change is overdue
  600–1,200 $
  Ad timing belt OM607timing belt K9K Mercedestiming belt kit OM607
• !! Timing belt interference engine -- total loss risk from 120,000 km

  The OM607 is an interference engine with a timing belt (Renault K9K). Mercedes specifies 200,000 km; Renault recommends 120,000 km for the same engine. If the belt snaps, pistons meet valves -- immediate engine destruction.

  Symptoms: Usually no warning before snap; sometimes faint squealing or rattling on cold start
  400–800 $
  Ad timing belt kit OM607timing belt K9K 1.5 dCi
• !! Injector failure K9K base from 100,000 km

  The Renault-based K9K diesel shows known injector weaknesses. Defective injectors cause poor combustion, increased soot production and drastically shorten DPF regeneration intervals.

  Symptoms: Rough idle, power loss, black smoke, frequent DPF regeneration, fault codes for individual cylinders
  300–900 $
  Ad fuel injector OM607fuel injector K9K 1.5 dCiA6070700087

+ 3 more engine weaknesses + vehicle weaknesses

Smaller displacement variant of the OM651. Same technology as the 2.1L but less torque. Known for injector seal issues and timing chain stretch.

• !! Piezo Injector Faults (220/250 CDI) from 80,000 km

  Quality issues with Delphi piezo injectors in the 220 CDI and 250 CDI: injectors fail prematurely. A service action replaced piezo injectors with solenoid injectors free of charge.

  Symptoms: Strong vibrations under acceleration, rough running, elevated fuel consumption, exhaust smoke
  1,500–3,500 $
  Ad Piezo-fuel injector OM651fuel injector OM651 CDIDelphi fuel injector OM651
• !! Chain Tensioner Failure with Oil Loss from 120,000 km

  The OM651 chain tensioner can fail and allow engine oil to escape. Mainly affects vehicles built February–November 2014 (recall). Simplex roller chain increases wear risk.

  Symptoms: Light rattling on cold start from the rear of the engine, oil loss, engine warning light
  1,200–2,500 $
  Ad OM651 chain tensionerA6510500800 timing chain kit OM651
• !! Particulate Filter Blockage with Short-Trip Use from 100,000 km

  The DPF on the OM651DE18 does not regenerate completely during pure short-trip driving and blocks. A motorway run at least every 2 weeks is required.

  Symptoms: DPF warning light, power reduction, engine oil diluted by unburnt fuel
  800–2,500 $
  Ad particulate filter OM651DPF OM651 CDIdiesel particulate filter OM651

+ 2 more engine weaknesses + vehicle weaknesses

Renault-based small diesel (K9K). Economical but with little power reserve. Prone to EGR fouling and DPF issues under pure short-trip use.

• !! Timing belt instead of chain -- maintenance obligation from 120,000 km

  The Renault K9K-based OM607 uses a timing belt that must be replaced every 120,000 km or 6 years. Neglecting the change leads to snapping and severe engine damage.

  Symptoms: No noticeable warning before snap -- sudden failure with no advance notice if change is overdue
  600–1,200 $
  Ad timing belt OM607timing belt K9K Mercedestiming belt kit OM607
• !! Timing belt interference engine -- total loss risk from 120,000 km

  The OM607 is an interference engine with a timing belt (Renault K9K). Mercedes specifies 200,000 km; Renault recommends 120,000 km for the same engine. If the belt snaps, pistons meet valves -- immediate engine destruction.

  Symptoms: Usually no warning before snap; sometimes faint squealing or rattling on cold start
  400–800 $
  Ad timing belt kit OM607timing belt K9K 1.5 dCi
• !! Injector failure K9K base from 100,000 km

  The Renault-based K9K diesel shows known injector weaknesses. Defective injectors cause poor combustion, increased soot production and drastically shorten DPF regeneration intervals.

  Symptoms: Rough idle, power loss, black smoke, frequent DPF regeneration, fault codes for individual cylinders
  300–900 $
  Ad fuel injector OM607fuel injector K9K 1.5 dCiA6070700087

+ 3 more engine weaknesses + vehicle weaknesses

Smaller displacement variant of the OM651. Same technology as the 2.1L but less torque. Known for injector seal issues and timing chain stretch.

• !! Piezo Injector Faults (220/250 CDI) from 80,000 km

  Quality issues with Delphi piezo injectors in the 220 CDI and 250 CDI: injectors fail prematurely. A service action replaced piezo injectors with solenoid injectors free of charge.

  Symptoms: Strong vibrations under acceleration, rough running, elevated fuel consumption, exhaust smoke
  1,500–3,500 $
  Ad Piezo-fuel injector OM651fuel injector OM651 CDIDelphi fuel injector OM651
• !! Chain Tensioner Failure with Oil Loss from 120,000 km

  The OM651 chain tensioner can fail and allow engine oil to escape. Mainly affects vehicles built February–November 2014 (recall). Simplex roller chain increases wear risk.

  Symptoms: Light rattling on cold start from the rear of the engine, oil loss, engine warning light
  1,200–2,500 $
  Ad OM651 chain tensionerA6510500800 timing chain kit OM651
• !! Particulate Filter Blockage with Short-Trip Use from 100,000 km

  The DPF on the OM651DE18 does not regenerate completely during pure short-trip driving and blocks. A motorway run at least every 2 weeks is required.

  Symptoms: DPF warning light, power reduction, engine oil diluted by unburnt fuel
  800–2,500 $
  Ad particulate filter OM651DPF OM651 CDIdiesel particulate filter OM651

+ 2 more engine weaknesses + vehicle weaknesses

Widely used Mercedes diesel with aluminium block and steel liner. High mileages possible but known for injector seal issues, timing chain stretch and EGR problems.

• !! Chain Tensioner Seal Leaking — Recall

  Over 100,000 vehicles recalled: the chain tensioner seal leaks, allowing engine oil to drip onto the exhaust system and potentially ignite.

  Symptoms: Dropping oil level, oil smell from engine bay, oily deposits under the vehicle, possible oil fire
  0–300 $
  Ad OM651 chain tensioner gasketMercedes OM651 chain tensioner gasketA6510500277
• !! Timing Chain Stretch (Simplex Chain) from 150,000 km

  The OM651 uses a simplex timing chain. With short-trip driving and overdue oil change intervals the chain stretches.

  Symptoms: Light rattling noise on cold start from the rear of the engine, no fault code stored
  1,200–3,000 $
  Ad timing chain OM651timing chain kit OM651A6510500077
• !! Piezo Injector Faults from 80,000 km

  Same Delphi piezo injector problems as in the DE18: 220 CDI and 250 CDI variants affected. Mercedes replaced them with solenoid injectors as part of a service action.

  Symptoms: Vibrations and rough running especially under acceleration, elevated fuel consumption
  1,500–3,500 $
  Ad Piezo-fuel injector OM651fuel injector OM651Delphi Piezo-fuel injector OM651

+ 3 more engine weaknesses + vehicle weaknesses

Widely used Mercedes diesel with aluminium block and steel liner. High mileages possible but known for injector seal issues, timing chain stretch and EGR problems.

• !! Chain Tensioner Seal Leaking — Recall

  Over 100,000 vehicles recalled: the chain tensioner seal leaks, allowing engine oil to drip onto the exhaust system and potentially ignite.

  Symptoms: Dropping oil level, oil smell from engine bay, oily deposits under the vehicle, possible oil fire
  0–300 $
  Ad OM651 chain tensioner gasketMercedes OM651 chain tensioner gasketA6510500277
• !! Timing Chain Stretch (Simplex Chain) from 150,000 km

  The OM651 uses a simplex timing chain. With short-trip driving and overdue oil change intervals the chain stretches.

  Symptoms: Light rattling noise on cold start from the rear of the engine, no fault code stored
  1,200–3,000 $
  Ad timing chain OM651timing chain kit OM651A6510500077
• !! Piezo Injector Faults from 80,000 km

  Same Delphi piezo injector problems as in the DE18: 220 CDI and 250 CDI variants affected. Mercedes replaced them with solenoid injectors as part of a service action.

  Symptoms: Vibrations and rough running especially under acceleration, elevated fuel consumption
  1,500–3,500 $
  Ad Piezo-fuel injector OM651fuel injector OM651Delphi Piezo-fuel injector OM651

+ 3 more engine weaknesses + vehicle weaknesses

Modular four-cylinder turbo of the first compact platform generation. Known for timing chain stretch and thermostat issues. Adequate power up to 156 hp.

• !! Camshaft Adjuster Solenoid Leaks — Oil in Wiring Harness from 90,000 km

  The sealing ring on the camshaft adjuster solenoid fails. Oil creeps by capillary action through the wiring harness and destroys lambda sensors and the ECU. Repair €1,700–€4,000.

  Symptoms: Lambda sensor fault codes, engine stumbling, CEL. In later stages multiple electrical faults simultaneously, ECU coated with oil
  1,700–4,000 $
  Ad Ölstoppkabel M270 camshaftnverstellercamshaftnmagnet A2740107900Abgasket camshaft W176 wiring loom
• !! Recall — Camshaft Break (Production Defect 2015)

  M270 engines with manufacturing date July–September 2015 have a defective weld seam on the camshaft lobe. Camshaft can break → engine damage. Recall with free replacement.

  Symptoms: Sudden engine noise, power loss up to engine stall. Only vehicles with production date July–September 2015 affected
  0–0 $
  Ad camshaft M270 recall replacementcamshaft M270 2015
• !! Electric Thermostat Failure from 90,000 km

  The electrically-controlled thermostat on the M270 fails frequently and is difficult to access at the rear of the engine. Replacement costs 800–1,300 EUR at Mercedes workshops.

  Symptoms: Engine does not reach operating temperature of 80°C, coolant temperature fluctuates, fault code P0128
  600–1,300 $
  Ad thermostat M270A2702000315Coolant thermostat M270

+ 4 more engine weaknesses + vehicle weaknesses

Modular four-cylinder turbo of the first compact platform generation. Known for timing chain stretch and thermostat issues. Adequate power up to 156 hp.

• !! Camshaft Adjuster Solenoid Leaks — Oil in Wiring Harness from 90,000 km

  The sealing ring on the camshaft adjuster solenoid fails. Oil creeps by capillary action through the wiring harness and destroys lambda sensors and the ECU. Repair €1,700–€4,000.

  Symptoms: Lambda sensor fault codes, engine stumbling, CEL. In later stages multiple electrical faults simultaneously, ECU coated with oil
  1,700–4,000 $
  Ad Ölstoppkabel M270 camshaftnverstellercamshaftnmagnet A2740107900Abgasket camshaft W176 wiring loom
• !! Recall — Camshaft Break (Production Defect 2015)

  M270 engines with manufacturing date July–September 2015 have a defective weld seam on the camshaft lobe. Camshaft can break → engine damage. Recall with free replacement.

  Symptoms: Sudden engine noise, power loss up to engine stall. Only vehicles with production date July–September 2015 affected
  0–0 $
  Ad camshaft M270 recall replacementcamshaft M270 2015
• !! Electric Thermostat Failure from 90,000 km

  The electrically-controlled thermostat on the M270 fails frequently and is difficult to access at the rear of the engine. Replacement costs 800–1,300 EUR at Mercedes workshops.

  Symptoms: Engine does not reach operating temperature of 80°C, coolant temperature fluctuates, fault code P0128
  600–1,300 $
  Ad thermostat M270A2702000315Coolant thermostat M270

+ 4 more engine weaknesses + vehicle weaknesses

Modular four-cylinder turbo of the first compact platform generation. Known for timing chain stretch and thermostat issues. Adequate power up to 156 hp.

• !! Camshaft Adjuster Solenoid Leaks — Oil in Wiring Harness from 90,000 km

  The sealing ring on the camshaft adjuster solenoid fails. Oil creeps by capillary action through the wiring harness and destroys lambda sensors and the ECU. Repair €1,700–€4,000.

  Symptoms: Lambda sensor fault codes, engine stumbling, CEL. In later stages multiple electrical faults simultaneously, ECU coated with oil
  1,700–4,000 $
  Ad Ölstoppkabel M270 camshaftnverstellercamshaftnmagnet A2740107900Abgasket camshaft W176 wiring loom
• !! Recall — Camshaft Break (Production Defect 2015)

  M270 engines with manufacturing date July–September 2015 have a defective weld seam on the camshaft lobe. Camshaft can break → engine damage. Recall with free replacement.

  Symptoms: Sudden engine noise, power loss up to engine stall. Only vehicles with production date July–September 2015 affected
  0–0 $
  Ad camshaft M270 recall replacementcamshaft M270 2015
• !! Electric Thermostat Failure from 90,000 km

  The electrically-controlled thermostat on the M270 fails frequently and is difficult to access at the rear of the engine. Replacement costs 800–1,300 EUR at Mercedes workshops.

  Symptoms: Engine does not reach operating temperature of 80°C, coolant temperature fluctuates, fault code P0128
  600–1,300 $
  Ad thermostat M270A2702000315Coolant thermostat M270

+ 4 more engine weaknesses + vehicle weaknesses

Modular four-cylinder turbo of the first compact platform generation. Known for timing chain stretch and thermostat issues. Adequate power up to 156 hp.

• !! Camshaft Adjuster Solenoid Leaks — Oil in Wiring Harness from 90,000 km

  The sealing ring on the camshaft adjuster solenoid fails. Oil creeps by capillary action through the wiring harness and destroys lambda sensors and the ECU. Repair €1,700–€4,000.

  Symptoms: Lambda sensor fault codes, engine stumbling, CEL. In later stages multiple electrical faults simultaneously, ECU coated with oil
  1,700–4,000 $
  Ad Ölstoppkabel M270 camshaftnverstellercamshaftnmagnet A2740107900Abgasket camshaft W176 wiring loom
• !! Recall — Camshaft Break (Production Defect 2015)

  M270 engines with manufacturing date July–September 2015 have a defective weld seam on the camshaft lobe. Camshaft can break → engine damage. Recall with free replacement.

  Symptoms: Sudden engine noise, power loss up to engine stall. Only vehicles with production date July–September 2015 affected
  0–0 $
  Ad camshaft M270 recall replacementcamshaft M270 2015
• !! Electric Thermostat Failure from 90,000 km

  The electrically-controlled thermostat on the M270 fails frequently and is difficult to access at the rear of the engine. Replacement costs 800–1,300 EUR at Mercedes workshops.

  Symptoms: Engine does not reach operating temperature of 80°C, coolant temperature fluctuates, fault code P0128
  600–1,300 $
  Ad thermostat M270A2702000315Coolant thermostat M270

+ 4 more engine weaknesses + vehicle weaknesses

More powerful 2.0L variant of the M270. Solid turbocharged four-cylinder with adequate performance. Oil consumption possible at high mileage.

• !! Camshaft Adjuster Solenoid Leaks — Oil in Wiring Harness from 90,000 km

  A leaking camshaft adjuster solenoid allows oil to migrate into the wiring harness. Lambda sensors die first, then the engine ECU. Well-known failure pattern on all M270 variants.

  Symptoms: Lambda fault codes, rough running, CEL. Oil smell in engine bay. In later stages multiple electrical faults
  1,700–4,000 $
  Ad Ölstoppkabel camshaftnmagnet M270camshaftnmagnet CLA250 undichtwiring loom camshaft A250 M270
• !! Recall — Camshaft Break (Production Defect 2015)

  M270DE20 engines with manufacturing date July–September 2015: defective weld seam on the camshaft lobe leads to fracture and engine damage. Recall with free replacement.

  Symptoms: Metallic noises from engine bay, power loss, in worst case engine stall
  0–0 $
  Ad camshaft M270DE20 recallcamshaft CLA250 Bruch 2015
• !! Electric Thermostat Failure from 90,000 km

  Identical issue to the M270DE16: electrically-controlled thermostat at the rear of the engine fails prematurely. Difficult removal drives workshop costs to 700–1,300 EUR.

  Symptoms: Engine runs permanently below operating temperature, coolant temperature fluctuations, fault code P0128
  700–1,300 $
  Ad thermostat M270DE20Coolant thermostat M270DE20

+ 4 more engine weaknesses + vehicle weaknesses

More powerful 2.0L variant of the M270. Solid turbocharged four-cylinder with adequate performance. Oil consumption possible at high mileage.

• !! Camshaft Adjuster Solenoid Leaks — Oil in Wiring Harness from 90,000 km

  A leaking camshaft adjuster solenoid allows oil to migrate into the wiring harness. Lambda sensors die first, then the engine ECU. Well-known failure pattern on all M270 variants.

  Symptoms: Lambda fault codes, rough running, CEL. Oil smell in engine bay. In later stages multiple electrical faults
  1,700–4,000 $
  Ad Ölstoppkabel camshaftnmagnet M270camshaftnmagnet CLA250 undichtwiring loom camshaft A250 M270
• !! Recall — Camshaft Break (Production Defect 2015)

  M270DE20 engines with manufacturing date July–September 2015: defective weld seam on the camshaft lobe leads to fracture and engine damage. Recall with free replacement.

  Symptoms: Metallic noises from engine bay, power loss, in worst case engine stall
  0–0 $
  Ad camshaft M270DE20 recallcamshaft CLA250 Bruch 2015
• !! Electric Thermostat Failure from 90,000 km

  Identical issue to the M270DE16: electrically-controlled thermostat at the rear of the engine fails prematurely. Difficult removal drives workshop costs to 700–1,300 EUR.

  Symptoms: Engine runs permanently below operating temperature, coolant temperature fluctuations, fault code P0128
  700–1,300 $
  Ad thermostat M270DE20Coolant thermostat M270DE20

+ 4 more engine weaknesses + vehicle weaknesses