The 2019 GLS63 AMG uses the M157 5.5L twin-turbo V8, a high-strung powerplant known for catastrophic engine failures due to defective connecting rod bearings and inadequate oiling under high load. This is a ticking time bomb that can grenade the entire bottom end without warning, turning a $100k SUV into a $40k repair bill.
M157 Connecting Rod Bearing Failure (Engine Grenade)
Common · high severity
Typical onset: 40,000-80,000 mi
Symptoms: Metallic knocking or rattling from engine bay at idle or under load, Metal shavings in oil during changes, Sudden catastrophic engine seizure with no warning, Low oil pressure warnings intermittently or permanently
Fix: Complete engine rebuild or replacement required. Rod bearings fail due to inadequate oil flow design and bearing material defects. Once knocking starts, you have days at best. Rebuild requires full disassembly, new bearings, resurfaced crank, new pistons typically, 40-60 labor hours. Many shops recommend short block replacement instead due to collateral damage.
Estimated cost: $25,000-45,000
Transmission Oil Cooler Leaks
Occasional · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: Transmission fluid pooling under vehicle, Low transmission fluid warnings on dash, Harsh shifting or delayed engagement when fluid gets low, Pink/red fluid visible near front of transmission bell housing area
Fix: External cooler lines or the cooler itself develop leaks at fittings or from physical degradation. Requires dropping the transmission pan, replacing cooler and lines, full fluid flush. 6-9 hours labor depending on access and whether pan needs removal.
Estimated cost: $1,800-3,200
Transmission Mounts Collapse
Common · medium severity
Typical onset: 50,000-90,000 mi
Symptoms: Clunking when shifting from Park to Drive or Reverse, Excessive vibration at idle in gear, Visible transmission sag or misalignment when inspected on lift, Thudding noise over bumps from driveline
Fix: Hydraulic transmission mounts fail from the sheer torque of the AMG V8. Requires supporting transmission, removing old mounts, installing OE replacements. 3-5 hours labor. Don't cheap out with aftermarket here—they fail faster.
Estimated cost: $900-1,600
Turbocharger Wastegate Rattle
Occasional · low severity
Typical onset: 70,000-110,000 mi
Symptoms: Rattling sound from engine bay on cold start, disappears when warm, Rattle during deceleration or light throttle, No performance loss initially, Check engine light with underboost codes if wastegate sticks
Fix: Wastegate actuator arms wear and develop play, causing rattle. Can eventually stick and cause overbost/underboost. Requires turbo removal and either actuator replacement or full turbo replacement if shaft is worn. 8-12 hours per side if doing both turbos.
Estimated cost: $3,500-6,500
Fuel Injector Carbon Buildup and Failure
Occasional · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: Rough idle or misfires on cold start, Check engine light with cylinder misfire codes, Loss of power or hesitation during acceleration, Fuel smell from engine bay in extreme cases
Fix: Direct injection leads to carbon buildup on intake valves and injector tips. Failed injectors require replacement, walnut blasting for carbon removal recommended simultaneously. Injectors alone are 4-6 hours, carbon cleaning adds another 6-8 hours if done properly with manifold removal.
Estimated cost: $2,800-5,500
Air Suspension Compressor and Strut Failures
Common · medium severity
Typical onset: 70,000-120,000 mi
Symptoms: Vehicle sits low on one corner or entirely, Compressor runs constantly or makes grinding noise, Suspension warning lights on dash, Inability to raise vehicle to normal height
Fix: Airmatic system is complex and expensive. Compressor failures and air strut leaks are inevitable. Compressor replacement is 3-4 hours, each strut is 2-3 hours. Most techs recommend doing all four struts at once if one fails at high mileage to avoid repeat labor.
Estimated cost: $2,200-4,800
Owner tips
Change oil every 5,000 miles MAX with quality 0W-40 synthetic—the M157 is brutal on oil and bearing longevity depends on it
Have a Blackstone oil analysis done every other change starting at 30k miles to catch bearing material before catastrophic failure
Budget $3k-5k annually for repairs after 60k miles—these are not cheap to maintain
Consider an extended warranty if buying used, specifically one that covers engine internals without a mileage exclusion
Avoid hard launches and sustained high RPM until engine is fully warmed—cold oil kills rod bearings faster
Only buy if you can afford a $30k+ engine replacement without blinking, or if it already has documented bearing upgrades—otherwise this is a financial grenade with luxury seats.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
Fitment notes: AGM battery required; located under hood on right side; auxiliary battery in rear cargo area
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Every control module on the 2018-2020 Mercedes-Benz GLS63 AMG — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
Transmission Control Unit (TCU)2.5 hr R&Rsecurity gateway +1.0 hr▸ programming details
⚠️ Trailer hitch and lighting control. Requires trailer detection calibration.
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2019 Mercedes-Benz GLS63 AMG 5.5L V8 BiTurbo M157 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.