The 2000 Mercury Mountaineer shares the Ford Explorer platform and its well-documented weaknesses: catastrophic 4.0L SOHC timing chain failures, transmission cooler line corrosion leading to trans death, and 4.6L V8 spark plug ejection issues. These aren't minor inconveniences—they're engine and transmission killers that often total the vehicle.
4.0L SOHC Timing Chain Cassette Failure
Common · high severity
Typical onset: 80,000-150,000 mi
Symptoms: Loud rattling on cold start that quiets after warmup, Engine misfires and rough running as guides disintegrate, Check engine light with cam/crank correlation codes, Catastrophic valve damage if chain jumps timing
Fix: Requires front engine disassembly to replace timing chains, cassettes, guides, tensioners, and water pump while you're in there. 12-16 hours labor. Often find piston/valve damage requiring head work or complete engine replacement if driven after symptoms appear.
Estimated cost: $2,800-5,500
Transmission Oil Cooler Line Corrosion and Cross-Contamination
Common · high severity
Typical onset: 90,000-140,000 mi
Symptoms: Strawberry milkshake appearance in coolant reservoir, Transmission slipping or erratic shifting, Overheating transmission or engine, Coolant loss with no visible external leaks
Fix: Steel cooler lines rust through inside the radiator, mixing coolant and ATF. Requires radiator replacement, complete transmission fluid system flush (often ineffective), and frequently a replacement transmission since coolant destroys clutches and seals. 8-10 hours if trans survives, 16-22 hours for trans replacement.
Estimated cost: $1,200-4,800
4.6L V8 Spark Plug Blowout
Occasional · high severity
Typical onset: 60,000-120,000 mi
Symptoms: Sudden loud hissing or popping sound from engine bay, Severe misfire on one cylinder, Loss of power and rough running, Visible spark plug and coil blown out of head
Fix: Two-piece spark plugs break on removal, and insufficient thread engagement allows plugs to blow out, destroying threads. Prevention: never let plugs go past 60k mi. Repair requires HeliCoil insert (2-3 hours per hole) or cylinder head removal for TimeSert repair (10-14 hours). If multiple cylinders affected, often cheaper to replace heads.
Estimated cost: $500-3,200
Front Control Arm Bushing and Ball Joint Failure
Common · medium severity
Typical onset: 70,000-110,000 mi
Symptoms: Clunking over bumps from front suspension, Wandering steering and poor alignment retention, Uneven tire wear on inside edges, Steering wheel vibration at highway speeds
Fix: Lower control arm bushings deteriorate and ball joints wear. Most shops replace entire control arms rather than pressing bushings. Both sides should be done together. 4-5 hours labor plus alignment.
Estimated cost: $800-1,400
Rear Axle Seal and Differential Bearing Failure
Occasional · medium severity
Typical onset: 100,000-160,000 mi
Symptoms: Gear oil dripping from rear axle seals onto brake drums, Howling or whining noise from rear on acceleration or deceleration, Clunking when shifting from park to drive, Contaminated rear brakes causing poor stopping
Fix: Axle seals leak, contaminate brakes, and if ignored, differential bearings fail. Requires axle seal replacement (2-3 hours) or full differential rebuild if bearings are gone (6-8 hours). Always replace rear brake shoes when seals leak.
Estimated cost: $600-2,200
4R70W Transmission Overdrive Band and Servo Failure
Common · high severity
Typical onset: 120,000-180,000 mi
Symptoms: Transmission slips or flares between 2nd and 3rd gear, No overdrive engagement or falls out of overdrive under load, Harsh 3-4 shift or no 3-4 shift at all, Burnt transmission fluid smell
Fix: Overdrive servo bore wears, causing band failure. Requires transmission removal and rebuild including servo bore repair kit, new band, and usually full clutch pack replacement. 12-16 hours labor.
Estimated cost: $2,200-3,800
Transfer Case Mode Selector Switch and Shift Motor Failure
Occasional · low severity
Typical onset: 80,000-140,000 mi
Symptoms: 4WD won't engage or disengage, Blinking 4WD lights on dash, Grinding or clicking from transfer case when selecting modes, Stuck in 4WD or 2WD mode
Fix: Electronic shift motor or dash switch fails. Shift motor replacement requires dropping exhaust and transfer case access (3-4 hours). Dash switch is simpler (1 hour). Verify which component failed before ordering parts.
Estimated cost: $400-900
Owner tips
If buying a 4.0L V6, verify timing chains were replaced with updated parts after 2002 TSB—if not done, budget for it immediately
Check coolant reservoir for any pink/brown discoloration indicating trans cooler failure—walk away if present
4.6L V8 owners: replace spark plugs every 50,000 miles maximum, use anti-seize, and let engine cool completely before removal
Flush transmission every 30,000 miles with Mercon V—the 4R70W does not have a lifetime fill despite what the manual says
Inspect rear axle seals during every brake job—catching leaks early prevents differential damage
Hard pass unless you're getting it nearly free and can wrench yourself—the timing chain and transmission cooler failures are budget-killers that strike without warning, and parts availability is declining fast.
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.
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ON CERTAIN PICKUP TRUCKS, PASSENGER VEHICLES, SPORT UTILITY VEHICLES, AND MOTOR HOMES CHASSIS, THE SPEED CONTROL DEACTIVATION SWITCH MAY, UNDER CERTAIN CONDITIONS, LEAK INTERNALLY AND THEN OVERHEAT, SMOKE, OR BURN.
Consequence: THIS COULD RESULT IN AN UNDERHOOD FIRE.
Remedy: DEALERS WILL INSTALL A FUSED WIRING HARNESS. OWNERS OF THE PASSENGER CARS INCLUDED IN THIS CAMPAIGN WILL BE INSTRUCTED TO RETURN THEIR VEHICLES TO THEIR DEALERS TO HAVE THE SPEED CONTROL DEACTIVATION SWITCH DISCONNECTED AS AN INTERIM REPAIR. AS SOON AS REPAIR PARTS ARE AVAILABLE (EXPECTED OCTOBER 2007), OWNERS WILL BE INSTRUCTED TO RETURN TO THE DEALERS FOR INSTALLATION OF A FUSED WIRING HARNESS. THE RECALL BEGAN ON AUGUST 13, 2007, AND MAILING COMPLETED BY SEPTEMBER 19, 2007. OWNERS MAY CONTACT FORD AT 1-888-222-2751.
FUEL SYSTEM, GASOLINE · 06E056000
2006-06-13
CERTAIN AFTERMARKET FUEL FILTERS SOLD UNDER THE PUROLATOR BRAND NAME, P/N F65277, SHIPPED FROM JANUARY 16 THROUGH JUNE 2, 2006, FOR USE ON THE ABOVE LISTED PASSENGER VEHICLES. DUE TO INCORRECT DESIGN, THE QUICK CONNECTORS MAY NOT FULLY SEAT WITH THE TUBE INTERFACE, EVEN THOUGH THE PERSON MAKING THE CONNECTION MAY BELIEVE THAT THE QUICK CONNECTOR IS FULLY ATTACHED.
Consequence: FAILURE OF THIS CONNECTION COULD LEAD TO FUEL SPILLAGE AND, IN THE PRESENCE OF AN IGNITION SOURCE, A FIRE COULD OCCUR.
Remedy: UFI WILL NOTIFY OWNERS AND REPLACE THE FILTERS FREE OF CHARGE. THE RECALL BEGAN ON AUGUST 4, 2006. OWNERS MAY CONTACT UFI FILTERS USA AT 800-230-5876.
VEHICLE SPEED CONTROL:CABLES · 03V280000
2003-08-05
ON CERTAIN SPORT UTILITY VEHICLES EQUIPPED WITH SPEED CONTROL AND 4.0L SOHC ENGINES, IF THE STRAND COVER ON THE SPEED CONTROL CABLE BECOMES FLARED AT THE END, THE SPEED CONTROL CABLE MAY BIND WHEN THE SPEED CONTROL IS ACTIVATED.
Consequence: THE THROTTLE RETURN SPRING FORCE MAY NOT BE SUFFICIENT TO OVERCOME THE BINDING CONDITION WHEN THE SPEED CONTROL IS DISENGAGED. BRAKING FUNCTION WOULD BE MAINTAINED THOUGH STOPPING DISTANCES MAY BE INCREASED.
Remedy: DEALERS WILL INSPECT THE SPEED CONTROL CABLE AND, IF NECESSARY, REPLACE IT. OWNER NOTIFICATION BEGAN AUGUST 29, 2003. OWNERS SHOULD CONTACT FORD AT 1-800-392-3673.
SEATS:FRONT ASSEMBLY:RECLINER · 03V281000
2003-08-05 · PE03020
ON CERTAIN SPORT UTILITY VEHICLES EQUIPPED WITH HIGH BACK SEATS, THE UPPER BOLT ON THE DRIVER'S SIDE HIGH BACK SEAT, THAT ATTACHES THE SEAT RECLINER MECHANISM TO THE SEAT BACK FRAME, COULD FRACTURE. IF THE BOLT FRACTURES AND DOES NOT JAM IN THE SEAT BACK FRAME, THE SEAT BACK MAY RECLINE UNTIL IT MAKES CONTACT WITH AN OBJECT BEHIND THE SEAT, SUCH AS THE SECOND ROW SEAT CUSHION.
Consequence: THE DRIVER COULD POTENTIALLY LOSE CONTACT WITH THE STEERING WHEEL OR FOOT PEDALS DURING SUCH AN EVENT, INCREASING THE RISK OF A CRASH.
Remedy: DEALERS WILL REPLACE THE DRIVER SEAT UPPER BOLT WITH A METAL SPACER AND BOLT. IN ADDITION, SEATS WITH TUBULAR BACK FRAMES WILL HAVE THE FULLY THREADED LOWER RECLINER BOLT REPLACED WITH A PARTIALLY THREADED BOLT. OWNER NOTIFICATION BEGAN ON AUGUST 29, 2003. OWNERS SHOULD CONTACT FORD AT 1-800-392-3673.
TIRES:TREAD/BELT · 00T005000
2000-08-21 · PE00020
TIRE DESCRIPTION: FIRESTONE WILDERNESS AT, SIZE P235/75R15, PRODUCED AT THE DECATUR, ILLINOIS TIRE PLANT AND ALL FIRESTONE RADIAL ATX AND RADIAL ATX II TIRES, SIZE P235/75R15. OPERATION OF THESE TIRES AT LOW INFLATION PRESSURES, HIGH SPEED, AND IN HOT WEATHER, CAN CONTRIBUTE TO SEPARATION OF THE TIRE TREAD.
Consequence: IF THE TREAD SEPARATES FROM THE TIRE, THE DRIVER CAN LOSE CONTROL OF THE VEHICLE, POSSIBLY RESULTING IN A CRASH CAUSING INJURY OR DEATH.
Remedy: THE REPLACEMENT/REIMBURSEMENT PROGRAM FOR THIS CAMPAIGN EXPIRED ON AUGUST 29, 2001. HOWEVER, CUSTOMERS SHOULD CONTACT FIRESTONE CUSTOMER SERVICE AT 1-800-465-1904 FOR POSSIBLE ASSISTANCE.
SEAT BELTS · 00V228001
2000-08-18
VEHICLE DESCRIPTION: PASSENGER VEHICLES, LIGHT DUTY TRUCKS, SPORT UTILITY VEHICLES, AND MINI VANS EQUIPPED WITH TRW SEAT BELT BUCKLE ASSEMBLIES. THE BUCKLE BASE OF THESE SEAT BELT ASSEMBLIES WERE NOT PROPERLY HEAT TREATED AND THEREFORE DO NOT PASS THE LOAD BEARING REQUIREMENT OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 209, "SEAT BELT ASSEMBLIES."
Consequence: IN THE EVENT OF A VEHICLE CRASH, THE OCCUPANT MAY NOT BE PROPERLY RESTRAINED.
Remedy: DEALERS WILL INSPECT THE DATE CODE ON CERTAIN SEAT BELT BUCKLES OF YOUR VEHICLE AND REPLACE ALL SEAT BELT BUCKLES THAT FALL WITHIN THE SUSPECT DATE CODE RANGE. OWNER NOTIFICATION BEGAN OCTOBER 26, 2000. OWNERS WHO TAKE THEIR VEHICLES TO AN AUTHORIZED DEALER ON AN AGREED UPON SERVICE DATE AND DO NOT RECEIVE THE FREE REMEDY WITHIN A REASONABLE TIME SHOULD CONTACT FORD AT 1-800-392-3673.
AIR BAGS:SIDE/WINDOW · 00V179000
2000-07-05
VEHICLE DESCRIPTION: 4-DOOR SPORT UTILITY VEHICLES EQUIPPED WITH SIDE AIR BAGS. THE SUBJECT VEHICLES HAVE A REVISED LEVEL SIDE CRASH SENSOR THAT COULD DEPLOY THE SIDE AIR BAG IF THE IGNITION KEY IS IN THE "RUN" POSITION AND THE SEATBELT WEBBING IS FORCIBLY EXTRACTED FROM A LOCKED RETRACTOR WITH A JERKING MOTION.
Consequence: INADVERTENT SIDE AIR BAG DEPLOYMENT COULD CAUSE PERSONAL INJURY TO THE SEAT OCCUPANT.
Remedy: DEALERS WILL REPLACE THE SIDE CRASH SENSORS WITH A REVISED DESIGN THAT WILL REDUCE THE LIKELIHOOD OF AN UNEXPECTED SIDE AIR BAG DEPLOYMENT.
ELECTRICAL SYSTEM:WIRING:FUSES AND CIRCUIT BREAKERS · 00V072000
2000-03-07 · PE99049
VEHICLE DESCRIPTION: MULTI-PURPOSE VEHICLES EQUIPPED WITH 4.0L ENGINES AND ALL-TIME 4-WHEEL DRIVE (A4WD) POWERTRAINS. THE GENERIC ELECTRONIC MODULE (GEM) COULD EXPERIENCE A CONDITION REFERRED TO AS "LOCK-UP" IN WHICH THE GEM CONTROLLED ELECTRONIC FUNCTIONS (E.G., FRONT WINDSHIELD WIPERS, INTERIOR LIGHTS, 4X4 SYSTEM, ETC.) COULD NOT BE TURNED ON OR, IN SOME CASES IF THE FUNCTION IS ON, COULD NOT BE TURNED OFF.
Consequence: AN INOPERATIVE WINDSHIELD WIPER SYSTEM COULD AFFECT DRIVER VISIBILITY, INCREASING THE RISK OF A CRASH.
Remedy: DEALERS WILL INSTALL A RESISTOR IN THE GEM CIRCUIT.
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