The 2018 Explorer sits on Ford's aging D4 platform in its final generation before the 2020 redesign. These are mechanically solid vehicles overall, but the 3.5L EcoBoost variants suffer from catastrophic engine failures due to coolant intrusion, while all models deal with PTU/transmission issues and some carbon monoxide cabin intrusion concerns.
3.5L EcoBoost Catastrophic Engine Failure (Coolant Intrusion)
Occasional · high severityTypical onset: 40,000-80,000 mi
Symptoms: White smoke from exhaust on cold start, Coolant loss with no visible leaks, Misfires and rough idle that progressively worsen, Milky oil on dipstick or oil cap, Sudden loss of power or engine seizure
Fix: Factory defect allows coolant to seep past cylinder head into combustion chamber, hydrolock and bearing damage follow. Requires complete engine replacement or full rebuild with updated head gaskets and machining. 18-24 labor hours for engine R&R plus rebuild time. Ford issued TSB 18-2327 but no recall despite class action lawsuit.
Estimated cost: $8,000-15,000
PTU (Power Transfer Unit) Failure
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: Grinding or whining noise from under vehicle center, Burning smell during operation, AWD malfunction warning light, Metal shavings in PTU fluid (check at every oil change), Complete loss of AWD or vehicle won't move
Fix: PTU runs hot and has inadequate fluid capacity for its workload, cooking itself to death. Ford has no dipstick or service interval despite 4,000-mile fluid life. Requires PTU replacement, cannot be rebuilt reliably. 4-6 hours labor. Preventive fluid changes every 30K miles extend life significantly.
Estimated cost: $1,800-2,800
Carbon Monoxide Cabin Intrusion
Occasional · high severitySymptoms: Exhaust smell inside cabin, Headaches or nausea during driving, CO detector alerts if you test the cabin, Worse with rear hatch open or in reverse
Fix: Design flaw allows exhaust gases to enter cabin through liftgate seal gaps and body panel seams. Multiple recalls and TSBs issued (18S32, 19S32). Ford drills drainage holes in liftgate and applies sealant to body seams, installs revised liftgate pivot brackets. 2-3 hours labor but effectiveness varies. Some owners never fully resolve it.
Estimated cost: $0-400
Transmission Shudder and Premature Wear (6F50/6F55)
Common · medium severityTypical onset: 50,000-90,000 mi
Symptoms: Vibration or shudder during light acceleration 25-45 mph, Harsh or delayed shifts, especially 3-4 and 4-5, Slipping sensation under load, Transmission overheat warnings
Fix: Six-speed automatic develops torque converter shudder and clutch pack wear. TSB 18-2388 calls for transmission fluid and filter change using Mercon ULV, often temporarily effective. Severe cases need torque converter replacement or full transmission rebuild. Fluid change: 2 hours, rebuild: 12-16 hours.
Estimated cost: $300-4,500
Water Pump Failure (All Engines)
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: Coolant leak from front of engine, Squealing or grinding noise from accessory belt area, Engine overheating, Coolant smell or visible drips under vehicle
Fix: Water pumps fail prematurely across all engine variants, plastic impellers and bearing seals deteriorate. Requires coolant drain, accessory removal, pump replacement. On 3.5L engines (especially EcoBoost) this is 4-5 hours due to tight packaging. Replace thermostat and hoses during same repair. Use OEM or premium aftermarket parts only.
Estimated cost: $600-1,100
Exhaust Manifold/Turbo Stud Failure (EcoBoost)
Occasional · low severityTypical onset: 60,000-120,000 mi
Symptoms: Loud ticking or tapping from engine bay that increases with RPM, Exhaust leak smell, Slight loss of power or boost, Visible soot around turbo/manifold junction
Fix: Exhaust manifold studs corrode and break due to heat cycles, creating exhaust leaks at turbo interface. Requires manifold removal, stud extraction (often broken flush), retapping threads. Driver side worse than passenger. 6-8 hours labor including broken stud extraction. Use high-quality stainless studs on reassembly.
Estimated cost: $800-1,400
Buy the naturally aspirated 3.5L V6 with documented PTU maintenance under 60K miles—skip the EcoBoost unless you enjoy engine replacement roulette.
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.