Mercedes-Benz CLS C257
Weaknesses, engine ratings and buying advice
The CLS C257 (2018–2024) is the most elegant Mercedes sedan of its era — and the last model in this lineage (production ended 2024). Buying a CLS means buying a future collector's piece.
Engine choice: OM654 (CLS 220d 143 kW / CLS 300d 180 kW) is the solid four-cylinder diesel. OM656 (CLS 350d 210 kW / CLS 400d 243–250 kW) is the diesel crown: inline-six, long-distance royalty. M256 (CLS 450 270 kW / AMG CLS 53 320 kW) with 48V EQ Boost is the petrol highlight — described as "the pinnacle of the combustion engine." M264 (CLS 350, 220 kW) is the four-cylinder petrol with 48V mild hybrid.
48V electrical system is the main topic: early models (2018–2019) had 48V battery failures causing breakdowns. Largely resolved from 2020. AIRMATIC is essentially mandatory — without air suspension the CLS misses its purpose.
Test-drive checklist: 48V system for error messages, AIRMATIC level after 30 min, enjoy inline-six refinement, MBUX stability.
2026 market: CLS 350d from $33,000–44,000. CLS 450 from $43,000–53,000. Prices falling sharply — good time to buy. Insider pick: CLS 350d (OM656) with AIRMATIC, 2020+ build.
435 PS
AMG CLS 53 · Benzin
CLS 53 — Cultured AMG Without V8 Pretensions
Fun to Drive!Generations
Engine Overview
The Mercedes-Benz CLS C257 is available with 9 engine variants — from 116 to 435 hp.
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 - !! 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 - !! 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
+ 8 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 - !! 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 - !! 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
+ 8 more engine weaknesses + vehicle weaknesses
Modern inline-six diesel with aluminium block and steel pistons. Efficient and powerful, few known weaknesses to date. Timing chain long-lived.
- !! Recall Coolant Pump — Fire Hazard (Action Code 2090008)
The vacuum-controlled coolant pump can develop leaks between the coolant and vacuum circuits. Coolant enters the EGR solenoid valves; an electrochemical reaction creates a fire hazard.
- !! Bosch CP4 Pump Sensitive to Fuel Quality from 120,000 km
The Bosch CP4 high-pressure pump is more sensitive to fuel contamination than its predecessors. Poor diesel quality can damage the pump and injectors.
Symptoms: Power loss, hesitation, injection system fault codes, in severe cases engine damage from metal swarf - !! Coolant Pump Leaking — Fire Risk (Recall) from 50,000 km
The switchable coolant pump does not reliably seal between the coolant and vacuum circuits. Coolant can overheat electrical solenoid valves — fire risk. Campaign code 2090008.
Symptoms: No direct driver symptoms — preventive recall. Possible coolant loss, electrical faults, unusual odour
+ 3 more engine weaknesses + vehicle weaknesses
Modern inline-six diesel with aluminium block and steel pistons. Efficient and powerful, few known weaknesses to date. Timing chain long-lived.
- !! Recall Coolant Pump — Fire Hazard (Action Code 2090008)
The vacuum-controlled coolant pump can develop leaks between the coolant and vacuum circuits. Coolant enters the EGR solenoid valves; an electrochemical reaction creates a fire hazard.
- !! Bosch CP4 Pump Sensitive to Fuel Quality from 120,000 km
The Bosch CP4 high-pressure pump is more sensitive to fuel contamination than its predecessors. Poor diesel quality can damage the pump and injectors.
Symptoms: Power loss, hesitation, injection system fault codes, in severe cases engine damage from metal swarf - !! Coolant Pump Leaking — Fire Risk (Recall) from 50,000 km
The switchable coolant pump does not reliably seal between the coolant and vacuum circuits. Coolant can overheat electrical solenoid valves — fire risk. Campaign code 2090008.
Symptoms: No direct driver symptoms — preventive recall. Possible coolant loss, electrical faults, unusual odour
+ 3 more engine weaknesses + vehicle weaknesses
Modern inline-six diesel with aluminium block and steel pistons. Efficient and powerful, few known weaknesses to date. Timing chain long-lived.
- !! Recall Coolant Pump — Fire Hazard (Action Code 2090008)
The vacuum-controlled coolant pump can develop leaks between the coolant and vacuum circuits. Coolant enters the EGR solenoid valves; an electrochemical reaction creates a fire hazard.
- !! Bosch CP4 Pump Sensitive to Fuel Quality from 120,000 km
The Bosch CP4 high-pressure pump is more sensitive to fuel contamination than its predecessors. Poor diesel quality can damage the pump and injectors.
Symptoms: Power loss, hesitation, injection system fault codes, in severe cases engine damage from metal swarf - !! Coolant Pump Leaking — Fire Risk (Recall) from 50,000 km
The switchable coolant pump does not reliably seal between the coolant and vacuum circuits. Coolant can overheat electrical solenoid valves — fire risk. Campaign code 2090008.
Symptoms: No direct driver symptoms — preventive recall. Possible coolant loss, electrical faults, unusual odour
+ 3 more engine weaknesses + vehicle weaknesses
Modern inline-six diesel with aluminium block and steel pistons. Efficient and powerful, few known weaknesses to date. Timing chain long-lived.
- !! Recall Coolant Pump — Fire Hazard (Action Code 2090008)
The vacuum-controlled coolant pump can develop leaks between the coolant and vacuum circuits. Coolant enters the EGR solenoid valves; an electrochemical reaction creates a fire hazard.
- !! Bosch CP4 Pump Sensitive to Fuel Quality from 120,000 km
The Bosch CP4 high-pressure pump is more sensitive to fuel contamination than its predecessors. Poor diesel quality can damage the pump and injectors.
Symptoms: Power loss, hesitation, injection system fault codes, in severe cases engine damage from metal swarf - !! Coolant Pump Leaking — Fire Risk (Recall) from 50,000 km
The switchable coolant pump does not reliably seal between the coolant and vacuum circuits. Coolant can overheat electrical solenoid valves — fire risk. Campaign code 2090008.
Symptoms: No direct driver symptoms — preventive recall. Possible coolant loss, electrical faults, unusual odour
+ 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 - !! 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 - !! 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
+ 6 more engine weaknesses + vehicle weaknesses
Four-cylinder turbo with 48V belt starter-generator. Modern, efficient engine with EQ Boost mild hybrid. Timing chain long-lived.
- !! Exhaust Valves Defective — Cylinder Head Damage (Serial Defect) from 60,000 km
Defective exhaust valves and soft valve guides lead to severe cylinder head damage. Often just after the warranty expires. Mercedes USA extended the warranty to 15 years/150,000 miles.
Symptoms: Sudden severe misfires, CEL flashing, power drop, dangerous stalling at motorway speed - !! HV Cables and E-Motor Integration Defective (PHEV) from 60,000 km
The electric motor is integrated into the 9G-Tronic. With faults in the high-voltage cables the gearbox must be removed — extremely costly repair.
Symptoms: Fault message 'Hybrid drivetrain disturbed', no electric drive possible, vehicle runs as pure combustion engine only, sometimes emergency shutdown - !! Chain Tensioner Loses Tension — Chain Rattling from 80,000 km
The hydraulic chain tensioner on the M264 can lose oil pressure after extended standstill. On cold start the timing chain rattles briefly until oil pressure builds.
Symptoms: Brief rattling on cold start (2–5 seconds), disappears after warm-up
+ 9 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 - !! 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 - !! 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
+ 6 more engine weaknesses + vehicle weaknesses
Vehicle Weaknesses
| Weakness | Cost | |
|---|---|---|
| Recall: turbocharger oil return line — fire risk Retaining screws for the turbocharger oil return line may be mixed up. Incorrect screws reduce clamping force, oil can escape and ignite. Symptoms: Oil smell in engine bay, smoke, in the worst case engine bay fire | Low |
Test Reports
TÜV Report 2024
The current CLS generation shows few faults at the MOT and robust engineering.
2023-11Top Reported Issues
Alternatives
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Known Problems and Issues +
A total of 45 weaknesses have been documented for the Mercedes-Benz CLS C257 (2018–2024) — 38 engine-related and 7 vehicle-related. Typical issues affect Other, Suspension, Electronics, Gearbox.
CLS (OM654, 2018–2024) — Be Careful: Rocker Arm and Camshaft Wear, Electric Coolant Pump Leaking — Recall, NOx Sensor Defective — AdBlue Fault and Start Inhibit. Power: 245 PS.
CLS (OM656, 2018–2024) — Be Careful: Recall Coolant Pump — Fire Hazard (Action Code 2090008), Bosch CP4 Pump Sensitive to Fuel Quality, Coolant Pump Leaking — Fire Risk (Recall). Power: 286 PS.
CLS (OM656, 2018–2024) — Be Careful: Recall Coolant Pump — Fire Hazard (Action Code 2090008), Bosch CP4 Pump Sensitive to Fuel Quality, Coolant Pump Leaking — Fire Risk (Recall). Power: 330 PS.
CLS (OM656, 2018–2023) — Be Careful: Recall Coolant Pump — Fire Hazard (Action Code 2090008), Bosch CP4 Pump Sensitive to Fuel Quality, Coolant Pump Leaking — Fire Risk (Recall). Power: 340 PS.
CLS (OM654, 2019–2024) — Be Careful: Rocker Arm and Camshaft Wear, Electric Coolant Pump Leaking — Recall, NOx Sensor Defective — AdBlue Fault and Start Inhibit. Power: 194 PS.
CLS (M256, 2018–2024) — Be Careful: 48V ISG Battery Failure, Camshaft Adjuster Solenoid Leaking — Oil in Wiring Harness, Elevated Oil Consumption at Higher Mileage. Power: 367 PS.
CLS (M256, 2018–2024) — Be Careful: 48V ISG Battery Failure, Camshaft Adjuster Solenoid Leaking — Oil in Wiring Harness, Elevated Oil Consumption at Higher Mileage. Power: 435 PS.
CLS (M264, 2018–2024) — Be Careful: Exhaust Valves Defective — Cylinder Head Damage (Serial Defect), HV Cables and E-Motor Integration Defective (PHEV), Chain Tensioner Loses Tension — Chain Rattling. Power: 299 PS.
What to watch out for with the Mercedes-Benz CLS? See the detailed listing of all engine and vehicle weaknesses in the sections above.
Frequently Asked Questions
What problems and weaknesses does the Mercedes-Benz CLS C257 have? +
What should I look for when buying a used Mercedes-Benz CLS C257? +
Which engine is recommended? +
Which Mercedes-Benz CLS C257 engine is the most fun? +
Is the Mercedes-Benz CLS C257 worth buying used? +
What horsepower variants are available for the Mercedes-Benz CLS C257? +
Last updated: February 2026 · All information without guarantee