The 2013 Ford Flex with the 3.5L EcoBoost is a comfortable family hauler with serious powertrain durability issues. The direct-injection EcoBoost engine suffers from catastrophic carbon buildup and timing chain problems, while the 6F50/55 transmission has a well-documented oil cooler design flaw that leads to internal contamination and failure.
PTU (Power Transfer Unit) Seal Leak and Failure
Common · high severity
Typical onset: 60,000-100,000 mi
Symptoms: Grinding or whining noise from front of vehicle during turns, Fluid leak visible on garage floor near front differential area, Binding sensation when turning at low speeds, Check AWD warning light
Fix: PTU seal leaks lead to fluid loss and bearing failure. If caught early, seal replacement is 3-4 hours. If run low on fluid, PTU replacement required at 6-8 hours. Often done with right axle seal and axle shaft (recalls exist for shaft failures). Many techs now replace PTU and rear diff fluid every 30k as prevention.
Symptoms: Transmission slipping or shuddering, Milky or strawberry-colored transmission fluid, Coolant in transmission or transmission fluid in coolant, Overheating or erratic shifting, Check engine light with transmission codes
Fix: The internal transmission oil cooler in the radiator fails, allowing coolant and ATF to cross-contaminate. Requires new radiator, complete transmission flush (often multiple flushes), and frequently a transmission rebuild or replacement because coolant destroys clutch packs. This is a 12-16 hour job when trans needs rebuild. Cooler-only repair if caught immediately: 4-5 hours plus extensive flushing.
Estimated cost: $1,200-5,500
EcoBoost Carbon Buildup and Intake Valve Coking
Common · medium severity
Typical onset: 50,000-90,000 mi
Symptoms: Rough idle and misfires, Loss of power and hesitation on acceleration, Check engine light with misfire codes (P0300-P0306), Poor fuel economy, Engine runs rough when cold
Fix: Direct injection means no fuel washing intake valves—carbon builds up heavily. Requires walnut blasting or manual cleaning of intake valves: 6-8 hours with manifold removal. Catch-can installation recommended as prevention (2 hours). Some engines develop severe buildup requiring head removal for proper cleaning, adding another 8-10 hours.
Estimated cost: $800-2,200
Timing Chain Stretch and Cam Phaser Failure
Occasional · high severity
Typical onset: 100,000-150,000 mi
Symptoms: Rattling noise on cold start that goes away when warm, Check engine light with cam/crank correlation codes (P0016, P0017, P0018), Rough running or stalling, Metal shavings in oil, Loss of power
Fix: EcoBoost engines stretch timing chains and wear cam phasers, especially if oil changes were extended. Requires timing chain replacement on both banks, new phasers, guides, and tensioners. This is a 16-20 hour job. Oil pump chain often replaced simultaneously. If chain jumped time, valve and piston damage likely—then you're looking at head work or short block replacement adding 25+ hours total.
Estimated cost: $3,500-8,000
Water Pump and Coolant Intrusion into Engine
Occasional · high severity
Typical onset: 70,000-110,000 mi
Symptoms: White smoke from exhaust on startup, Coolant loss with no external leaks, Rough idle and misfires, Coolant in oil (milky dipstick), Overheating
Fix: Internal water pump can fail and leak coolant into the cylinders through the timing cover. Pump replacement is 8-10 hours (requires timing cover removal). If coolant entered cylinders significantly, you need head gasket work or full engine rebuild depending on damage—30+ hours for short block replacement. Early catch crucial.
Estimated cost: $1,800-7,500
Fuel Pump Driver Module Failure
Occasional · medium severity
Symptoms: No start or extended crank time, Engine stalling while driving, Loss of power under load, Intermittent starting issues, Check engine light with fuel pressure codes
Fix: Fuel pump driver module (FPDM) mounted to the frame rail fails due to corrosion or component failure. Module replacement is 1-2 hours. Sometimes fuel pump itself also needs replacement (add 3 hours for in-tank pump). Recalls exist for fuel delivery issues—check VIN first.
Estimated cost: $400-1,200
Owner tips
Change oil every 5,000 miles maximum with quality synthetic—EcoBoost engines are hard on oil and timing components
Service PTU and rear differential every 30,000 miles regardless of manual recommendations
Install aftermarket transmission cooler bypass to eliminate internal radiator cooler risk—$300-500 investment that saves transmissions
Consider dual catch-can setup for PCV and CCV systems to reduce carbon buildup—about $400 installed
Monitor coolant level religiously; unexplained loss means internal water pump leak investigation immediately
Avoid unless you're getting it cheap and have a $5,000 repair fund—the EcoBoost and transmission issues are deal-breakers for most used buyers, and preventive maintenance costs are high.
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.
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Ford Motor Company (Ford) is recalling certain 2013-2018 Lincoln MKT and Ford Flex and Taurus vehicles with the Police Interceptor or SHO Performance Pack. The rear suspension toe links may fracture due to stress on the rear suspension.
Consequence: A fractured rear toe link will cause a sudden change in vehicle handling and increase the risk of a crash.
Remedy: Ford will notify owners, and dealers will replace the rear suspension toe links, free of charge. Remedy parts are not currently available. Owners were notified about the recall on March 3, 2020. A second notice will be mailed when remedy parts become available, which is currently expected to be the end of September 2020. The recall began October 28, 2020. Owners may contact Ford customer service at 1-866-436-7332 or Lincoln customer service at 1-800-521-4140. Ford's number for this recall is 20S04.
Ford Motor Company (Ford) is recalling certain model year 2013-2015 Ford Taurus, Ford Flex, Lincoln MKS and Lincoln MKT vehicles equipped with 3.5L GTDI Ecoboost engines and 2013-2015 Ford Taurus Police Interceptor vehicles. A component within the fuel pump electric module (PEM) may overheat causing a loss of electrical power to the fuel pump.
Consequence: A loss of power to the fuel pump will cause the engine to stall or prevent the vehicle from starting, increasing the risk of a crash.
Remedy: Ford will notify owners, and dealers will inspect the fuel PEM part number and replace the fuel PEM, as necessary, free of charge. The recall began on December 1, 2016. Owners may contact Ford customer service at 1-866-436-7332. Ford's number for this recall is 16S31.
FUEL SYSTEM, GASOLINE · 15V812000
2015-12-02
Ford Motor Company (Ford) is recalling certain model year 2013 Explorer, Explorer Police Utility, Taurus, Taurus Police Interceptor, Flex, Lincoln MKS, and Lincoln MKT vehicles. In the affected vehicles, the fuel delivery module may crack, allowing fuel to leak.
Consequence: A fuel leak in the presence of an ignition source may result in a fire.
Remedy: Ford will notify owners, and dealers will replace the fuel delivery module, free of charge. The recall began on December 21, 2015. Owners may contact Ford customer service at 1-866-436-7332. Ford's number for this recall is 13S04-S1.
STEERING:ELECTRIC POWER ASSIST SYSTEM · 15V340000
2015-06-02 · PE14030
Ford Motor Company (Ford) is recalling certain model year 2011-2012 Ford Fusion vehicles without a 3.5L engine and Lincoln MKZ hybrid electric vehicles, 2011 Mercury Milan vehicles, 2011-2012 Ford Taurus, Ford Flex, Lincoln MKS, and Lincoln MKT vehicles equipped with a 3.5L GTDI engine and 2013 Ford Taurus, Ford Flex, Lincoln MKS, and Lincoln MKT vehicles equipped with any available engine. The affected vehicles have electric power steering assist systems that may shut down as a result of a steering motor sensor fault.
Consequence: If the vehicle experiences a loss of power steering assist, extra steering effort will be required at lower speeds, increasing the risk of a vehicle crash.
Remedy: Ford will notify owners, and dealers will check the Power Steering Control Module (PSCM) for Diagnostic Trouble Codes (DTC). If dealers find any loss of steering assist DTCs, the steering gear will be replaced, free of charge. If, no codes are found during the PSCM inspection, the PSCM software will be updated, free of charge. The recall began on July 21, 2015. Owners may contact Ford customer service at 1-866-436-7332. Ford's number for this recall is 15S18.
POWER TRAIN:AXLE ASSEMBLY:AXLE SHAFT · 14V393000
2014-07-02
Ford Motor Company (Ford) is recalling certain model year 2012-2014 Ford Edge and Lincoln MKX vehicles manufactured September 2, 2010, to November 30, 2013; 2013-2014 Ford Taurus and Lincoln MKS vehicles manufactured August 25, 2011, to November 30, 2013; and 2013-2014 Ford Flex and Lincoln MKT vehicles manufactured September 12, 2011, to November 30, 2013. In the affected vehicles, the halfshaft retention circlip may not have been properly installed, and as a result, the halfshaft may move outward and disengage from the linkshaft while driving and without prior warning.
Consequence: If the halfshaft and linkshaft become disengaged while driving, power will no longer be transmitted to the wheels, increasing the risk of a vehicle crash. Additionally, if the parking brake is not applied before exiting the vehicle, the vehicle may roll away despite the transmission being placed in 'Park', increasing the risk of injury to exiting occupants and bystanders.
Remedy: Ford will notify owners, and dealers will inspect the vehicles to make sure that the halfshaft is properly retained. If it is not, dealers will replace the linkshaft and also replace the halfshaft if it shows evidence of spline damage, free of charge. The recall began on August 4, 2014. Owners may contact Ford customer service at 1-800-392-3673. Ford's number for this recall is 14S10.
FUEL SYSTEM, GASOLINE · 13V227000
2013-05-31
Ford is recalling certain model year 2013 Explorer, Taurus, Flex, Fusion, Police Interceptor Sedan and Police Interceptor Utility vehicles; and certain model year 2013 Lincoln MKS, MKT, and MKZ vehicles. In the affected vehicles, the fuel delivery module may develop a crack, allowing fuel to leak.
Consequence: A fuel leak in the presence of an ignition source may result in a fire.
Remedy: Ford will notify owners, and dealers will replace the fuel delivery module, free of charge. The recall began on July 20, 2013. Owners may contact Ford Motor Company Customer Relationship Center at 1-866-436-7332. Ford's recall campaign number is 13S04.
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