The 2020 McLaren 720S is a hand-built supercar with McLaren's M840T twin-turbo V8. When maintained properly, it's thrilling and surprisingly usable, but early M840T engines had catastrophic piston and bore scoring issues that can grenade the motor—often under warranty but devastating if outside coverage.
M840T Engine Piston Ring and Cylinder Bore Failure
Occasional · high severityTypical onset: 5,000-25,000 mi
Symptoms: Excessive oil consumption (more than 1 qt per 1,000 mi), Blue smoke on cold start or hard acceleration, Misfire codes (P0300 series) and rough idle, Catastrophic rod knock or bearing failure if ignored
Fix: Complete engine rebuild with updated piston rings, honed cylinders, and often full short-block replacement. McLaren issued a Technical Service Bulletin and extended warranty coverage for many units. Rebuild takes 60-80 hours including drop, disassembly, machine work, and reinstallation. If out of warranty, this is bankruptcy-level repair.
Estimated cost: $45,000-75,000
Transmission Oil Cooler Leaks
Common · medium severityTypical onset: 15,000-40,000 mi
Symptoms: Transmission fluid puddles under car (red/pink fluid), Transmission overheating warnings on dash, Harsh or delayed shifts when hot, Burning smell after spirited driving
Fix: Oil cooler line o-rings fail or cooler itself develops pinhole leaks. Replace cooler and lines, flush system, refill with expensive Fuchs Titan DCTF transmission fluid. 8-12 hours labor including undertray removal and system bleeding.
Estimated cost: $2,800-4,500
Hydraulic Lift System Failure
Occasional · medium severitySymptoms: Front lift won't raise or lowers randomly while driving, Hydraulic pump runs constantly or whines loudly, Dash warning: 'Vehicle Lift System Fault', Scraping on driveways or speed bumps
Fix: Hydraulic pump, accumulator, or solenoid valve failure. Pump is under front clamshell and requires significant disassembly. Bleed system and reset adaptations with McLaren diagnostic tool. 6-10 hours labor depending on component.
Estimated cost: $3,500-6,000
Fuel Tank and Filler Neck Seal Issues (Recall)
Occasional · high severitySymptoms: Fuel smell in cabin or near rear of car, Visible fuel staining around filler cap area, Check engine light with evaporative emission codes, Fuel gauge reading erratically
Fix: NHTSA recall for fuel tank sealing issues. McLaren replaces tank seals and filler neck components. Covered under recall at dealer, but if you're doing it yourself post-recall or on non-recalled VIN, tank removal requires full rear clamshell removal. 12-16 hours labor.
Estimated cost: $0 (recall) or $4,000-7,000
Dual-Clutch Transmission Shift Solenoid and Mechatronic Faults
Occasional · medium severityTypical onset: 30,000-60,000 mi
Symptoms: Harsh 2-3 or 3-4 shifts, especially when cold, Transmission refuses to shift or goes into limp mode, Dash warning: 'Transmission Fault - Drive with Care', Grinding or clunking during gear changes
Fix: Solenoid pack or mechatronic unit failure in the 7-speed SSG dual-clutch. Requires transmission removal or lowering, solenoid replacement, software adaptation with McLaren MDARS tool. Clutch packs may also need inspection/replacement if contaminated by metal debris. 15-25 hours labor.
Estimated cost: $6,000-12,000
Brake Line Corrosion and Hydraulic Hose Degradation (Recall)
Rare · high severitySymptoms: Soft or spongy brake pedal feel, Brake fluid leaks visible at calipers or hard lines, Brake warning light or ABS fault codes, Increased stopping distances
Fix: NHTSA recall for brake line corrosion in certain climate zones. McLaren inspects and replaces affected lines. If outside recall scope, replacing corroded hard lines and hydraulic hoses requires significant disassembly of undertrays and suspension components. Full system bleed mandatory. 8-14 hours labor.
Estimated cost: $0 (recall) or $3,000-5,500
Only buy with McLaren extended warranty or if you can afford a $60K engine rebuild as an "oops"—stunning machine, but early M840T grenades make this a financial trap without coverage.
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.