2010 MERCURY MOUNTAINEER

Typical onset: 80,000-150,000 mi

Symptoms: Rattling on cold start that fades after 10-15 seconds, Check engine light with cam/crank correlation codes (P0340, P0344), Rough idle and power loss as wear progresses, Catastrophic engine failure if chain jumps timing

Fix: Replace both timing chain cassettes, tensioners, guides, cam phasers, and oil pump drive. Requires front cover removal and often new water pump while you're in there. 10-14 labor hours. This is THE killer on these V6s—the plastic cassette guides break apart.

Estimated cost: $2,200-3,800

Typical onset: 70,000-120,000 mi

Symptoms: Transmission fluid in coolant (strawberry milkshake in overflow tank), Coolant in transmission pan (death sentence for clutches), Sudden slipping, no reverse, or complete transmission failure, Overheating transmission after cooler leak starts

Fix: Requires radiator replacement, external cooler installation, transmission flush or rebuild depending on contamination severity. If coolant entered trans, you're looking at rebuild/replacement (12-16 hours). Many shops now install auxiliary cooler as preventive on these 5R55S units.

Estimated cost: $800-1,200 radiator only, $3,500-5,500 with transmission rebuild

Typical onset: 60,000-100,000 mi

Symptoms: Clunking over bumps from front end, Wandering steering or loose feel on highway, Uneven tire wear on inside edges, Visible cracking or tearing on rubber bushings during inspection

Fix: Replace both lower control arms as assemblies (bushings alone are a nightmare on these). 3-4 hours plus alignment. This platform eats bushings faster than the older Explorers due to revised geometry.

Estimated cost: $600-900

Typical onset: 80,000-140,000 mi

Symptoms: Gear oil drips on driveway under rear axle, Visible wetness around pinion yoke and driveshaft connection, Whining noise from rear if fluid level drops significantly, Burnt gear oil smell on highway driving

Fix: Replace pinion seal, check pinion bearing preload, refill with correct friction modifier synthetic. 2-3 hours. Must get pinion torque right or you'll be back in there for bearing noise. Check axle breather tube—if clogged, it'll blow the seal again.

Estimated cost: $350-550

Typical onset: null

Symptoms: Misfire on single cylinder after plug change, Compression loss on one cylinder, Hissing sound from valve cover area under load, Plug feels loose or won't torque properly during installation

Fix: HeliCoil or TIME-SERT thread repair kit installation. If caught early, 1.5-2.5 hours per hole with head on vehicle. These aluminum heads strip easily if plugs are over-torqued or cross-threaded. Anti-seize and proper torque (13 ft-lbs) are critical.

Estimated cost: $250-450 per cylinder

Typical onset: null

Symptoms: Rear climate control only works on high speed, No air flow from rear vents on lower settings, Intermittent rear blower operation, Burning smell from rear cargo area (less common)

Fix: Replace rear blower motor resistor module located behind right rear quarter trim panel. 1-1.5 hours. Check blower motor itself—if drawing excessive current due to worn bearings, it'll burn out resistors repeatedly.

Estimated cost: $200-350

Typical onset: null

Symptoms: Driver or passenger seat back collapses rearward unexpectedly, Recliner handle feels loose or doesn't engage, Seat back won't lock in upright position, Grinding or clicking from seat frame when adjusting

Fix: Covered under NHTSA recall 14V-355 for certain VINs—check recall status first. If not covered, requires seat frame recliner mechanism replacement. 2-3 hours labor. Ford used updated parts with stronger pawl springs.

Estimated cost: $0 if recall applies, $400-650 if not