Mercedes-AMG Service and Repair in Dallas

Why do the M157 and M177 turbo V8s use oil and plugs so fast?

The M157 5.5 biturbo in the 2012–2018 E63, S63 and CLS63 mounts its turbochargers outside the vee, and its oil consumption comes from turbo seals, the crankcase breather and oil lines that cook against the exhaust. The coolant pipes in the vee of the M157 also fail and the smell arrives before any drip. A measured consumption test tells us whether the engine is within tolerance before anything comes apart.

The M177 and its dry-sump sibling the M178 moved the turbos into the vee, which shortened the intake path and raised the temperature around the plugs. Spark plugs on these engines last a fraction of a base-model interval, coils follow, and a misfire under boost after a spirited drive is almost always ignition. The M178 in the GT also needs its oil checked by the hot dry-sump procedure; a cold reading is meaningless.

The MCT transmission behind both engines is a 722.9 with a wet start-up clutch pack in place of the torque converter. A shudder from a stop or a slipping launch is the clutch pack or its adaptation, and we service it with the AMG fluid and reset the clutch values. Where the clutch or the conductor plate is out of range the parts are quoted from the 722.9 ranges on this page.

How is the M139 four-cylinder serviced differently?

The M139 in the CLA45, GLA45 and the current 43 models is the highest-output production four-cylinder Mercedes has built, and it runs cylinder pressures that punish spark plugs and injectors. Short trips around Lakewood or Highland Park foul plugs faster than highway miles, and the symptom is hesitation on throttle or high-pressure fuel codes that come and go.

The 43 variants add a 48-volt belt starter-generator and an electric turbocharger, so a battery warning or a boost fault can trace to the electrical side rather than the engine. We run the XENTRY quick test first and follow the component that logged the first fault. The 8G-DCT behind the 45 models has its own fluid and clutch adaptation, and the 9G-Tronic behind the 43s needs the same care as on the base cars.

Carbon on the intake valves is the long-term item on any direct-injection four-cylinder and the M139 is no exception. A gradual loss of top-end pull with clean fuel trims and good plugs points to valve deposits, which we confirm with a borescope through the intake port. Walnut-shell cleaning restores the airflow and the job is planned alongside a plug change so the intake is only opened once. On a car that is driven hard but briefly, the deposits build faster than the mileage would predict, so the borescope check is part of every B service on these engines.

Which fluids, brakes and parts are AMG-specific?

An AMG is not a base model with more power, and the service schedule reflects it. The oil grade is specified per engine, the spark plug interval is shorter, the MCT and DCT fluids are their own part numbers and the brake fluid spec is held to the AMG schedule. Using the base-model interval on an M156 or an M177 is the fastest way to turn a service item into a repair.

Brakes are the other place the schedule changes. AMG composite rotors and drilled faces heat-check, and the crack length has a specification, so we measure cracks as well as thickness. Pads on a two-ton car that stops hard in traffic on the Dallas North Tollway wear quickly, and the sensors trigger early enough that a visual check at every service avoids a surprise.

Tires and alignment belong on the same list. AMG cars run staggered sizes with wide rears, and the rear camber the factory specifies wears the inside shoulder well before the tread depth suggests a problem. We read the alignment on any AMG that comes in for brakes, because a car that is eating its rear tires is also loading one side of the rotors unevenly, and the two complaints usually arrive together.

Every AMG repair here is covered for 2 years parts and 2 years labor, up to 24,000 miles, nationwide. For a written range on an M156, M157, M177 or M139 car, email service@mercedesbenzrepair.net with the year, model and the symptom you are seeing.