2010 LINCOLN NAVIGATOR

Typical onset: 80,000-150,000 mi

Symptoms: Cold-start rattle for 2-5 seconds that sounds like marbles in a can, Check engine light with P0340-P0349 cam sensor codes, Rough idle and reduced power, Metal shavings in oil if severely degraded

Fix: Requires front engine tear-down to replace both cam phasers, timing chains, guides, and tensioners. Often done with spark plugs since you're already there. 12-16 labor hours depending on whether you need special tools to break the notorious spark plugs loose without snapping them.

Estimated cost: $2,800-4,500

Typical onset: 70,000-120,000 mi

Symptoms: Transmission fluid looks pink and milky (coolant mixing), Engine coolant looks reddish or oily, Transmission slipping or delayed engagement, Overheating transmission, Strawberry milkshake appearance in either fluid

Fix: The internal transmission cooler in the radiator fails and cross-contaminates fluids, which destroys the transmission rapidly. Requires radiator replacement, complete transmission fluid system flush (including torque converter and lines), often a new transmission if not caught immediately. External aux cooler should be added. 8-12 hours for cooler/flush, add 18-24 hours if transmission needs rebuild.

Estimated cost: $1,200-2,000 (caught early) or $4,500-7,000 (transmission damaged)

Typical onset: 60,000-100,000 mi

Symptoms: Not a failure itself but becomes one during maintenance, Misfire codes if plugs are overdue, Rough idle and poor fuel economy when plugs age out

Fix: The 2-piece spark plug design is infamous for breaking the ceramic portion off in the cylinder head during removal. Requires special extractors and adds 2-4 hours labor if multiple break. Some techs pre-soak with penetrant overnight. If it drops into cylinder, you're pulling the head. Plugs should be changed at 60k-70k max to avoid carbon buildup bonding them in.

Estimated cost: $400-600 (normal change) or $800-1,500 (with extractions)

Typical onset: 90,000-140,000 mi

Symptoms: Gear oil leak at pinion yoke (front of differential), Whining or howling noise from rear that changes with speed, Clunking on acceleration if bearing play is severe

Fix: The pinion seal leaks first, then bearing wears if driven low on fluid. Seal alone is 2-3 hours, but if bearing is worn you're looking at differential disassembly and carrier bearing/pinion bearing replacement. 6-8 hours for full bearing service. Many shops replace seal and bearings together since you're already in there.

Estimated cost: $400-700 (seal only) or $1,200-1,800 (bearings included)

Typical onset: 80,000-130,000 mi

Symptoms: Humming or grinding noise from front that increases with speed, ABS/traction control warning lights, Wheel play when jacked up and rocked top to bottom

Fix: The integrated hub bearing units fail, often one side first then the other within 20k miles. Straightforward bolt-on replacement. 2-2.5 hours per side. Do both sides if one fails at high mileage to avoid a second visit soon.

Estimated cost: $500-800 per side

Typical onset: 100,000-150,000 mi

Symptoms: Rear sags overnight or after sitting, Suspension warning light, Compressor runs constantly or won't run at all, Hissing from air lines under vehicle

Fix: The air suspension system develops leaks at bag connections or the compressor wears out. Compressor replacement is 3-4 hours, air springs are 2-3 hours each, lines vary. Many owners convert to traditional coil springs to eliminate ongoing air suspension costs. Conversion kits run $800-1,200 installed.

Estimated cost: $800-1,400 (compressor) or $1,500-2,500 (multiple components)