The 2015 Lincoln MKT shares the Ford Flex platform and suffers from catastrophic EcoBoost engine failures plus chronic transmission cooler leaks that can destroy the 6F50/6F55 six-speed automatic. The 3.7L naturally-aspirated V6 is significantly more reliable, but transmission issues affect all variants.
EcoBoost 3.5L Twin-Turbo Catastrophic Engine Failure
Common · high severityTypical onset: 80,000-130,000 mi
Symptoms: sudden loss of power under load, metallic knocking from engine, coolant mixing with oil (milky dipstick), white smoke from exhaust, check engine light with misfire codes
Fix: Carbon buildup on intake valves (direct injection problem) leads to pre-ignition and detonation that cracks cylinder walls, blows head gaskets, or destroys pistons. Complete engine rebuild or replacement required. 18-25 labor hours for replacement with used/reman long block.
Estimated cost: $8,000-15,000
Transmission Oil Cooler Internal Leak
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: transmission slipping or harsh shifts, delayed engagement into gear, milkshake-colored transmission fluid, radiator overflow reservoir contaminated with trans fluid, complete transmission failure if driven after coolant intrusion
Fix: Internal cooler in radiator corrodes and allows coolant into transmission fluid, which destroys clutch packs and valve body. Requires radiator replacement, complete transmission flush or rebuild, and all cooler lines. If caught early, flush and radiator may save trans (6-8 hours). If driven after contamination, full transmission rebuild needed (12-16 hours).
Estimated cost: $1,200-2,500 for early catch, $4,000-6,500 for rebuild
PTU (Power Transfer Unit) Failure
Occasional · high severityTypical onset: 70,000-110,000 mi
Symptoms: grinding or whining noise from center of vehicle, vibration during acceleration, AWD malfunction warning, loss of AWD capability, metal shavings in PTU fluid
Fix: The PTU on AWD models has no dipstick and owners rarely service it. Fluid breaks down, bearings fail, and unit grenades. Requires PTU replacement and often right-side axle seal work. 6-9 labor hours depending on access.
Estimated cost: $2,200-3,800
Water Pump Failure (EcoBoost models)
Common · high severityTypical onset: 60,000-90,000 mi
Symptoms: coolant leak from front of engine, squealing noise from accessory drive, overheating, coolant warning light, steam from engine bay
Fix: Internal water pump driven by timing chain fails and dumps coolant into crankcase or leaks externally. On EcoBoost engines this is an internal component requiring timing cover removal, timing chain work, and often leads to discovering stretched timing chains. 8-12 labor hours.
Estimated cost: $1,800-3,200
Rear Suspension Lower Control Arm Bushing Failure
Common · medium severityTypical onset: 50,000-80,000 mi
Symptoms: clunking over bumps from rear, wandering or loose steering feel, uneven rear tire wear, rear end feels unstable in corners, visible cracked or torn bushings on inspection
Fix: Rear lower control arm bushings deteriorate and allow excessive movement. Often both sides need replacement. Arms typically replaced as assemblies since bushings aren't serviceable separately on most aftermarket parts. 3-4 labor hours for both sides.
Estimated cost: $800-1,400
Turbochger Wastegate Rattle and Failure
Occasional · medium severityTypical onset: 70,000-120,000 mi
Symptoms: rattling noise on cold start that disappears when warm, loss of power under acceleration, excessive black smoke, check engine light with boost control codes, turbo whistle or whine
Fix: Wastegate actuator arms wear and rattle, or wastegate flapper sticks open/closed. Often both turbos need replacement since they're original units with similar wear. Each turbo is 6-8 labor hours due to tight engine bay packaging.
Estimated cost: $2,500-4,500 per turbo
Fuel Pump Driver Module Failure
Occasional · high severitySymptoms: no start condition, engine dies while driving, intermittent stalling, long crank before starting, fuel pump not priming (no hum from tank)
Fix: The fuel pump driver module mounted to the frame rail near fuel tank fails due to corrosion or internal component failure. Module replacement is straightforward once located. Subject to recall but failures still occur. 1-2 labor hours.
Estimated cost: $400-700
Avoid EcoBoost models entirely — the 3.7L V6 is marginally acceptable if you can verify religious maintenance and preventive radiator replacement, but even then expect expensive AWD and transmission issues.
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.