Mercedes-Benz AMG GLA 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.
GLA 45 S AMG — Brutal SUV
310 kW / 421 hp in the GLA: excess in every sense — overwhelmingly fast, but the SUV format costs the final degree of purity.
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
The 8-speed DCT in the GLA H247 occasionally shows jerky gear changes and delayed response when pulling away, particularly on cold starts in the GLA 180 and GLA 200. Problems increase from 50,000–100,000 km.
The reversing camera on the GLA H247 fails from around 30,000 km due to software errors or defective cable connections. Image appears with a delay, flickers or stays black.
On GLA H247 with power tailgate, sensors or actuators fail from around 50,000 km. Tailgate no longer opens or closes automatically.
Rear camera failures reported after 2–3 years or 25,000–40,000 km. Cause is often software errors or faulty cable connections.
GLA H247 with power tailgate shows sensor or drive motor failures from approx. 50,000 km. The tailgate can then no longer be opened or closed electrically.
In the GLA H247 the MBUX system occasionally restarts twice at the start of a journey. Additionally the brake assist and high-beam assist can deactivate themselves.
Like the predecessor X156, H247 owners report annoying wind noise at motorway speeds. Seals at the A-pillar or doors are usually the cause.
Reports & Tests
3 owner complaints filed with NHTSA (2020–2025). Most reported: Brakes (2), Powertrain (2), Hydraulic (1).