The 2016 Navigator uses Ford's 3.5L EcoBoost V6 exclusively (the 5.4L Triton ended in 2014). While powerful and sophisticated, this twin-turbo engine has known weaknesses around timing components, carbon buildup, and cooling system stress that can lead to catastrophic internal failures if neglected.
Timing Chain Stretch and Phaser Failure Leading to Catastrophic Engine Damage
Occasional · high severityTypical onset: 80,000-150,000 mi
Symptoms: Cold-start rattle lasting 3-5 seconds that worsens over time, Check engine light with cam/crank correlation codes (P0008, P0017, P0018), Loss of power and rough idle as phasers fail, Catastrophic failure: metal shavings in oil, complete loss of power
Fix: If caught early (just noise), replace both timing chains, guides, tensioners, and variable cam phasers—roughly 18-22 hours labor. If internal damage occurred (piston/valve contact), you're looking at complete engine rebuild or replacement with short block. Many shops won't rebuild due to labor cost exceeding reman engine price.
Estimated cost: $4,500-7,500 preventive / $12,000-18,000 after internal damage
Carbon Buildup on Intake Valves Causing Misfires and Power Loss
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Rough idle and hesitation on acceleration, Multiple cylinder misfire codes (P0300 series), Reduced fuel economy (2-3 MPG drop), Turbo lag becomes more pronounced
Fix: Direct injection means fuel never washes intake valves. Requires walnut blasting intake ports with manifolds removed—8-10 hours labor. Some techs also clean turbos and throttle body while in there. Cannot be fixed with fuel additives despite marketing claims.
Estimated cost: $800-1,400
Turbocharger Wastegate Rattle and Eventual Turbo Failure
Occasional · high severityTypical onset: 90,000-130,000 mi
Symptoms: Rattling/buzzing noise on acceleration (wastegate actuator), Underboost codes P0299 or overboost codes P0234, Blue/white smoke from exhaust (turbo seal failure), Oil consumption increases significantly, Loss of power especially under load
Fix: Wastegate actuators can sometimes be replaced separately (6-8 hours per side), but most failures occur alongside bearing wear requiring full turbo replacement. With twins, many shops recommend doing both simultaneously despite added cost—one fails, the other is close behind. 12-16 hours for both turbos.
Estimated cost: $2,800-4,200 single turbo / $4,500-6,800 both
Transmission Oil Cooler Line Leaks and Cooler Failure
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: Pink or red fluid puddle under vehicle (transmission fluid in coolant), Transmission overheating warnings on dash, Milky/strawberry-colored fluid on dipstick (coolant mixing with trans fluid), Harsh shifts or delayed engagement after fluid contamination
Fix: The cooler is integrated into the radiator on these. If just lines are leaking, 2-3 hours to replace. If cooler itself fails and fluids mix, you need radiator replacement PLUS complete transmission flush (possibly filter/pan service)—8-10 hours total. Contaminated fluid can destroy clutch packs if not addressed immediately.
Estimated cost: $600-1,200 lines only / $1,800-2,800 with radiator and flush
Power Brake Booster Vacuum Pump Failure
Occasional · high severityTypical onset: 80,000-120,000 mi
Symptoms: Hard brake pedal requiring excessive force, Grinding or whining noise from engine bay, Check engine light with low brake booster vacuum codes, Brake pedal sinks slowly to floor when held at stop
Fix: EcoBoost doesn't generate enough vacuum at idle for traditional brake booster, uses electric vacuum pump. When pump fails, braking becomes dangerous. Pump replacement is 3-4 hours (tight quarters behind engine). This was subject to a TSB and extended warranty coverage through some periods—check with dealer before paying out of pocket.
Estimated cost: $800-1,400
PTU (Power Transfer Unit) Fluid Leak and Bearing Failure
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Whining or grinding noise during acceleration (AWD engaged), Fluid leak from front of transfer case area, Vibration through drivetrain at highway speeds, AWD malfunction warning on dash
Fix: The PTU transfers power to front axle and is known for seal leaks leading to low fluid and bearing damage. Seal replacement alone is 2-3 hours. If bearings are damaged, full PTU replacement required at 4-6 hours. Ford has no dipstick or service interval for this—must drop fill plug to check, and many owners never do until it's too late.
Estimated cost: $400-700 seal / $1,200-2,000 full unit
Only buy if you have $3,000-5,000 set aside for timing/turbo work and can commit to rigorous maintenance—powerful truck but the EcoBoost can grenade without warning if neglected.
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.