2021 LINCOLN MKX

Typical onset: 60,000-100,000 mi

Symptoms: rough idle and misfires on cold starts, loss of power under load, check engine light with P0300-series codes, excessive oil consumption

Fix: Direct injection engines accumulate intake valve carbon. Severe cases lead to valve seat recession and cracked cylinder heads requiring both heads replaced. Walnut blasting intake valves is 4-6 hours labor; head gasket job on both banks runs 18-24 hours with machining.

Estimated cost: $4,500-8,500

Typical onset: 80,000-120,000 mi

Symptoms: grinding or whining noise from front of vehicle during acceleration, AWD malfunction warning, burning smell from undercarriage, vibration at highway speeds

Fix: Ford's AWD system PTU has no drain plug and many owners never service it. Fluid breaks down, bearings seize, unit grenades. Replacement is 4-6 hours labor. Always service PTU fluid every 30k miles on these.

Estimated cost: $2,200-3,200

Typical onset: 70,000-110,000 mi

Symptoms: transmission slipping or delayed engagement, milky or strawberry-colored transmission fluid, overheating transmission, coolant loss with no external leaks

Fix: Internal cooler in the radiator fails, mixing coolant into transmission fluid and destroying clutch packs. Requires new radiator, full transmission fluid flush (possibly multiple flushes), and often transmission rebuild. Cooler replacement is 3-4 hours; if trans is damaged, add 12-18 hours for rebuild.

Estimated cost: $1,800-6,500

Typical onset: 60,000-90,000 mi

Symptoms: coolant leak from front of engine, overheating, squealing or grinding noise from timing cover area, steam from under hood

Fix: Water pump is internal, driven by timing chain. Failure dumps coolant into crankcase or causes overheating that warps heads. Requires timing chain cover removal, new pump, chains, and tensioners as preventive measure. 10-14 hours labor.

Estimated cost: $2,800-4,200

Typical onset: 50,000-90,000 mi

Symptoms: long cranking before starting, loss of power and bucking under acceleration, P0087 low fuel pressure codes, engine stalling at idle

Fix: High-pressure fuel pump on 2.7L fails, sometimes contaminating the entire fuel system. Requires pump replacement (3-4 hours), fuel filter, and potentially injector cleaning or replacement. Contamination cases double the cost.

Estimated cost: $1,200-3,500

Typical onset: 60,000-100,000 mi

Symptoms: clunk when shifting from park to drive, vibration at idle in gear, excessive movement felt during acceleration, rattling from under vehicle over bumps

Fix: Hydraulic transmission mount fails, causing driveline vibration and harsh shifts. Mount replacement is straightforward, 1.5-2.5 hours labor. Often accompanied by failing engine mounts on higher-mileage examples.

Estimated cost: $400-800