Mercedes-Benz AMG CLA 45 S
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.
CLA 45 S Shooting Brake
310 kW in the Shooting Brake — 421 hp and boot space. For family men with motorsport DNA.
Engine Weaknesses 6
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
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
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
Individual owners report coolant temperature warnings at high-speed driving. Diagnosis: faulty coolant pump or sensor. Isolated cases, no systematic problem known.
Symptoms: Coolant temperature warning on display, especially at high speed (170+ km/h)
Despite combined direct and port injection the M139 can build up deposits on intake valves under intensive use. Considerably less than pure DI engines.
Symptoms: Slight hesitation at part throttle, minimal power loss, rarely noticeable
The M139 shows elevated oil consumption under high-load operation. As a high-performance engine with 7.0-litre oil capacity, regular oil level checks are mandatory.
Symptoms: Dropping oil level between service intervals, slight oil smell on hot engine
Vehicle Weaknesses 7
On CLA C118 from the production period August 2019 to July 2020, the turbocharger oil supply line could develop a leak. Oil reached the underbody and the road surface, increased fire risk.
On CLA C118 model year 2020, the voltage supply to the electric power steering assistance could be impaired. In the worst case the steering servo assistance failed while driving.
The 8-speed dual clutch gearbox in the CLA C118 occasionally shows rough gear changes, especially when downshifting and in crawl mode. Software updates help temporarily; clutch packs wear at higher mileages.
The optional Multibeam LED headlights fail or function only partially. Malfunctions affect the adaptive light distribution.
On CLA C118 models with Multibeam LED headlights, occasional malfunctions occur: the high beam assist deactivates unintentionally, or individual LED segments fail.
Starter battery is the most common breakdown cause on the CLA C118. The many assistance and comfort systems place a heavy load on the battery.
A frequent complaint on the CLA C118 and simultaneously the A-Class W177 is clearly audible fuel sloshing in the tank, especially at partial and low fill levels in corners.