The 2021 Nautilus shares the CD6 platform with Ford Edge and inherits some serious Ford EcoBoost vulnerabilities, particularly catastrophic internal engine failures on the 2.7L twin-turbo V6. The 2.0L EcoBoost is more reliable but still has cooling system weaknesses.
2.7L EcoBoost V6 Catastrophic Engine Failure
Occasional · high severityTypical onset: 40,000-80,000 mi
Symptoms: sudden loss of power under load, metallic knocking from engine bay, oil pressure warning light, engine seizure without warning, coolant mixing with oil
Fix: Complete engine replacement or full internal rebuild required. Ford issued TSB 21-2316 for piston ring land fractures and carbon buildup causing rod bearing failure. 18-25 labor hours for short block replacement, up to 35 hours for complete teardown rebuild with head work.
Estimated cost: $8,500-15,000
Transmission Oil Cooler Line Leaks
Common · medium severityTypical onset: 50,000-90,000 mi
Symptoms: transmission fluid puddles under vehicle, burnt transmission fluid smell, slipping between gears, overheating transmission, low fluid warning messages
Fix: The quick-connect fittings on cooler lines crack or the cooler itself develops pinhole leaks where lines connect. Replace both lines and cooler assembly as a set to prevent repeat failures. 2.5-3.5 hours labor. Often requires dropping subframe for access.
Estimated cost: $650-1,200
PTU (Power Transfer Unit) Fluid Leak and Failure
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: grinding noise during acceleration, AWD malfunction warning, fluid leak at front of transmission, vibration at highway speeds, binding sensation in tight turns
Fix: The PTU on AWD models runs hot and Ford's service intervals are inadequate. Seal leaks lead to low fluid and bearing destruction. If caught early, reseal and fluid change (1.5 hours). If bearings are damaged, complete PTU replacement required (4-5 hours). Must drop front subframe.
Estimated cost: $400-2,800
Coolant Intrusion into Cylinders (2.0L EcoBoost)
Occasional · high severityTypical onset: 70,000-110,000 mi
Symptoms: white smoke from exhaust on cold start, repeated coolant loss with no visible leaks, rough idle when cold, misfires on cylinders 2 or 3, oil looks milky on dipstick
Fix: Head gasket failure where coolant passages meet combustion chambers, common on cylinder 2. Requires cylinder head removal, resurfacing, new head gasket and head bolts. If caught late, cylinder wall scoring requires bore and oversize pistons. 12-16 hours labor for head gasket job alone.
Estimated cost: $2,800-4,500
Rear Transmission Mount Collapse
Common · low severityTypical onset: 45,000-75,000 mi
Symptoms: clunk when shifting from park to drive, excessive vibration at idle in gear, loud bang during hard acceleration, visible drooping of rear of engine
Fix: The hydraulic rear motor mount separates internally. Common on all Ford CD6 platform vehicles. Straightforward replacement, but requires supporting transmission. 1.5-2 hours labor.
Estimated cost: $350-550
Fuel System Carbon Buildup (Direct Injection)
Common · low severityTypical onset: 60,000-90,000 mi
Symptoms: rough idle, hesitation on acceleration, reduced fuel economy, misfires at startup, check engine light with multiple misfire codes
Fix: Direct injection means no fuel washing intake valves. Carbon accumulates on valve backs. Requires walnut blasting of intake ports with manifold removed. 4-5 hours labor. Preventive service, not a hard failure.
Estimated cost: $500-800
Active Park Assist and Camera Failures
Occasional · low severitySymptoms: park assist unavailable message, frozen or distorted camera image, parking sensors false alarms, system completely non-functional in rain
Fix: Water intrusion into front camera module or rear parking assist module. Camera modules fail internally and require replacement (1 hour). Parking sensor modules need reprogramming after replacement. NHTSA recall 21V-624 addresses backup camera software but hardware failures still occur.
Estimated cost: $400-900
Pass on 2.7L V6 models entirely due to engine grenading risk; 2.0L EcoBoost versions are acceptable if PTU and cooling system have documented maintenance, but factor $2,000-3,000 repair budget into purchase price.
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.