The 2018 Lincoln MKT shares the Ford Flex platform and comes with either a naturally aspirated 3.7L V6 or the problematic 3.5L EcoBoost V6. The EcoBoost variant has significant engine longevity concerns that can turn catastrophic, while both suffer from transmission cooling and PTU issues common to Ford AWD crossovers.
3.5L EcoBoost Catastrophic Engine Failure (Carbon Buildup & Timing Chain)
Occasional · high severityTypical onset: 80,000-140,000 mi
Symptoms: rough idle and misfires, loss of power under acceleration, rattling noise on cold start, check engine light with multiple misfire codes, metal shavings in oil
Fix: Direct injection causes extreme carbon buildup on intake valves leading to misfires; timing chain tensioners and phasers fail causing internal damage. Walnut blasting valves runs 6-8 hours labor but doesn't address phaser issues. Most need short block or complete engine replacement at 18-25 hours labor plus core.
Estimated cost: $8,000-14,000
Transmission Oil Cooler Line Failure
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: transmission fluid leaking near radiator, milky or pink fluid in coolant reservoir, transmission slipping or delayed engagement, overheating transmission
Fix: The internal transmission cooler inside the radiator corrodes and ruptures, mixing coolant and ATF which destroys the 6F50/6F55 transmission. Must replace radiator, flush both systems, and often rebuild transmission if contamination occurred. Total job runs 12-16 hours if transmission is damaged.
Estimated cost: $3,500-7,500
Power Transfer Unit (PTU) Seal Leaks and Failure
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: fluid dripping from center of vehicle, whining or grinding noise during turns, vibration at highway speeds, burning smell
Fix: PTU seals leak and owners don't check the fluid (no dipstick, requires pump). Runs dry and grenades itself. Seal replacement is 3-4 hours but often discovered too late. PTU replacement runs 6-8 hours including fluid and seals.
Estimated cost: $800-2,800
Transmission Mounts Collapsing
Common · low severityTypical onset: 65,000-95,000 mi
Symptoms: clunk when shifting from park to drive, excessive vibration at idle, visible engine movement when accelerating, transmission seems to shift hard
Fix: Hydraulic transmission mount fails allowing excessive drivetrain movement. Simple replacement takes 2-3 hours. Often done with other work since symptoms are tolerable but annoying.
Estimated cost: $400-650
Water Pump Failure (3.5L EcoBoost)
Occasional · high severityTypical onset: 80,000-120,000 mi
Symptoms: coolant leak from front of engine, overheating, whining or grinding noise from belt area, steam from under hood
Fix: Water pump fails without warning and can cause severe overheating. Replacement requires significant disassembly on the EcoBoost due to tight packaging. Runs 5-7 hours labor. Critical to not drive when overheating to avoid head gasket damage.
Estimated cost: $1,200-1,800
Rear Suspension Lower Control Arm Bushings
Occasional · low severityTypical onset: 75,000-110,000 mi
Symptoms: clunking over bumps in rear, unusual tire wear on rear tires, vehicle feels unstable or loose in rear, alignment won't hold
Fix: Rear lower control arm bushings deteriorate causing alignment issues and handling problems. Usually replace entire arms rather than press bushings. Both sides run 3-4 hours labor.
Estimated cost: $800-1,200
Skip the EcoBoost model entirely due to engine failure risk; the 3.7L V6 is more reliable but still carries Ford AWD drivetrain baggage that requires diligent maintenance.
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.