2018 MCLAREN 720S

Typical onset: 15,000-40,000 mi

Symptoms: Sudden loss of power and limp mode during spirited driving or track sessions, White smoke from exhaust indicating coolant consumption, Metal debris in oil during routine changes, Cylinder misfire codes (P0300 series) that don't clear, Catastrophic failure: thrown rod, cracked block, total loss of compression

Fix: Early M840T engines had inadequate piston ring tension and oil control, leading to ring flutter under high RPM. Rings break, score cylinder walls, then pistons crack or rods snap. McLaren issued a technical service bulletin and extended warranty coverage through 2024 for affected VINs. Repair requires full engine-out rebuild: pistons, rings, honing/re-sleeving cylinders, bearings, gaskets. Factory recommends short-block replacement. Expect 60-80 labor hours for removal, rebuild, and reinstallation.

Estimated cost: $35,000-65,000

Symptoms: Transmission overheat warning on dash during track use or aggressive driving, Visible transmission fluid leaking from front undertray, Burnt ATF smell after spirited runs, Transmission enters limp mode and won't shift past 3rd gear, Fluid level drops rapidly requiring frequent top-ups

Fix: The SSG transmission oil cooler lines are routed near exhaust and use crimped fittings prone to vibration fatigue. Lines crack or fittings separate, dumping fluid and causing rapid overheating. Requires lift removal of undertray, replacement of cooler lines and sometimes the cooler itself if contaminated. Flush system and refill with McLaren-spec fluid. Common preventive upgrade is braided stainless lines. 8-12 labor hours including fluid service.

Estimated cost: $3,500-6,000

Typical onset: 25,000-60,000 mi

Symptoms: Hard shifts or delayed engagement, especially when cold, Transmission fault codes P0750-P0770 (shift solenoid performance), Grinding or clunking during upshifts under load, Intermittent refusal to engage reverse or 1st gear, Limp mode restricting to 4th gear only

Fix: The SSG uses hydraulic actuators and solenoids to control clutch packs. Solenoids fail from heat cycling and contaminated fluid. Actuator seals weep internally. Diagnosis requires McLaren IRIS diagnostic tool to read transmission module. Typical fix is solenoid pack replacement (all six as a set) and actuator reseal or replacement. Transmission must be lowered for access. 10-14 labor hours.

Estimated cost: $4,500-7,500

Symptoms: Strong fuel odor in cabin or near rear quarter panels, Visible fuel staining on undertray after parking, Fuel gauge reading erratically or showing less than actual, Check engine light with evaporative emission codes (P0442, P0456), Fuel puddle under vehicle after fillup

Fix: NHTSA recall 19V-545 addressed fuel tank seam welds that can crack, causing leaks. Even post-recall, fuel filter housing O-rings and quick-connect fittings at the tank fail from thermal cycling. Carbon tub must be partially disassembled to drop the tank. Recall repair is dealer-only; tank replacement covered. Non-recall leaks require tank drop, seal replacement, sometimes new fuel pump module. 12-18 hours for tank R&R.

Estimated cost: $2,000-8,000

Typical onset: 20,000-50,000 mi

Symptoms: Clunking from center tunnel during aggressive throttle applications, Vibration at idle or during hard acceleration, Visible play in transmission when rocking car in gear, Misalignment of shift linkage causing gear selection issues

Fix: The 720S uses hydraulic transmission mounts that isolate the SSG from the carbon tub. Mounts tear internally or leak fluid, allowing excessive movement. Requires lift, exhaust removal, and underbody panel access. Replace all mounts as a set to maintain balance. OEM parts only; aftermarket options not reliable. 6-9 labor hours.

Estimated cost: $3,000-5,000

Typical onset: 30,000-70,000 mi

Symptoms: Deep knocking sound from lower engine at idle, louder under load, Low oil pressure warning intermittently or consistently, Metal shavings visible on magnetic drain plug, Oil consumption increases suddenly (1 qt per 500 mi), Engine eventually seizes or throws rod

Fix: High-RPM use with low or degraded oil causes main bearing wear. Some early engines had inadequate oil pump pressure under sustained high-G cornering. Diagnosis requires oil analysis and bearing inspection. Repair is full engine-out rebuild: crank polishing or replacement, bearing set, line boring if journals are damaged. Often discovered during piston ring failure teardown. 70+ labor hours for full rebuild.

Estimated cost: $40,000-70,000