The 2017 SL63 AMG with the M157 5.5L twin-turbo V8 is a high-performance roadster plagued by catastrophic engine failure issues related to defective crankshaft bolt failures and oil cooler seal deterioration. When maintained meticulously these are fantastic machines, but the engine grenading risk makes this a high-stakes ownership proposition.
Crankshaft Bolt Failure Leading to Complete Engine Destruction
Occasional · high severityTypical onset: 40,000-80,000 mi
Symptoms: Catastrophic engine failure with metal shavings throughout oil system, Sudden loss of power and metallic knocking before complete shutdown, No warning prior to failure in most cases, Oil pressure warning light immediately before catastrophic failure
Fix: The M157 crankshaft bolts can stretch and fail, causing the crankshaft to walk and destroy bearings, pistons, and block. Requires complete engine replacement or full rebuild with updated bolt kit. 35-50 hours labor for long block R&R plus machine work if rebuilding. Mercedes issued updated bolts but many engines still have originals.
Estimated cost: $25,000-45,000
Transmission Oil Cooler Seal Failure
Common · high severityTypical onset: 50,000-90,000 mi
Symptoms: Transmission fluid mixing with coolant creating strawberry milkshake appearance, Transmission slipping or harsh shifting after contamination, Coolant level dropping without external leaks, Check engine light with transmission-related codes
Fix: The MCT transmission oil cooler seals deteriorate and allow cross-contamination between cooling system and transmission fluid. Requires oil cooler replacement, complete transmission fluid flush (multiple times), and often transmission overhaul if caught late. 8-12 hours for cooler and flushes, add 20-30 hours if transmission needs rebuild.
Estimated cost: $3,500-8,000
Engine Main and Rod Bearing Wear
Occasional · high severityTypical onset: 60,000-100,000 mi
Symptoms: Cold-start knock that disappears after warmup, Metallic ticking or knocking under load, Low oil pressure at idle when hot, Metal particles visible in oil during changes
Fix: The M157 is sensitive to oil change intervals and quality. Extended intervals or wrong oil spec leads to bearing wear. Requires engine removal, complete teardown, crank polishing or replacement, and bearing replacement. 40-55 hours labor plus machine work.
Estimated cost: $15,000-28,000
Transmission Mount Failure
Common · medium severityTypical onset: 45,000-75,000 mi
Symptoms: Clunking when shifting from Park to Drive or Reverse, Excessive drivetrain vibration especially under acceleration, Visible sagging of transmission when inspected on lift, Metallic thud during hard downshifts
Fix: The hydraulic transmission mount fails from the engine's torque and heat cycles. Requires transmission support and mount replacement. Straightforward job at 2-3 hours labor.
Estimated cost: $800-1,400
Head Gasket Failure (Both Banks)
Rare · high severityTypical onset: 70,000-110,000 mi
Symptoms: White smoke from exhaust on cold starts, Coolant consumption without visible leaks, Rough idle or misfires on one bank, Overheating under load or sweet smell from exhaust
Fix: While less common than bearing issues, head gasket failure does occur especially if engine has been overheated. Requires heads removal, resurfacing, new gaskets and bolts. 18-24 hours labor per side, often done as preventive on both banks simultaneously.
Estimated cost: $8,000-14,000
Turbocharger Wastegate Rattle and Failure
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Rattling noise on cold starts lasting 3-10 seconds, Loss of boost pressure and reduced power, Check engine light with underboost codes P0299, Excessive smoke under hard acceleration
Fix: Wastegate actuator rods wear and create rattle, eventually the wastegate fails to seal causing boost loss. Requires turbocharger removal and rebuild or replacement. 8-12 hours per turbo. Often both are done simultaneously as preventive.
Estimated cost: $4,500-8,000
Only buy if you can afford a $30k-40k engine replacement without blinking, have full service records proving religious 5k oil changes, and the crankshaft bolt update is documented—otherwise this is a financial time bomb wrapped in gorgeous sheetmetal.
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.