The 2004 Explorer is a body-on-frame SUV built on the UN152 platform. The 4.0L SOHC V6 is plagued by timing chain cassette failures and head gasket issues, while both engines share transmission cooler and 5R55 automatic weaknesses that can grenade the unit if ignored.
4.0L SOHC Timing Chain Cassette Failure
Common · high severity
Typical onset: 80,000-150,000 mi
Symptoms: rattling on cold start that quiets after warmup, check engine light with camshaft position codes, rough idle and loss of power, catastrophic engine damage if chain jumps timing
Fix: Requires front cover removal to replace both cassettes, guides, tensioners, and chains. Book time is 8-10 hours; most shops replace water pump and front seals while in there. Engine damage from jumped timing means rebuild or replacement.
Estimated cost: $1,800-2,800 for preventive replacement; $4,000-6,500 for engine rebuild if damage occurs
Transmission Oil Cooler Line Failure Inside Radiator
Common · high severity
Typical onset: 60,000-120,000 mi
Symptoms: transmission fluid in coolant (strawberry milkshake appearance), coolant in transmission fluid, slipping or no movement after radiator leak, overheating transmission
Fix: Internal cooler in radiator corrodes and allows fluid mixing. Requires radiator replacement, full trans flush, often filter and fluid. If coolant contaminated the trans, rebuild or replacement needed. 3-4 hours for radiator and flush; add 12-16 hours if trans rebuild required.
Estimated cost: $800-1,200 for radiator and flush only; $2,500-4,000 if transmission rebuild needed
5R55W/S Transmission Intermediate Servo Bore Wear
Common · medium severity
Typical onset: 90,000-140,000 mi
Symptoms: harsh 2-3 shift or slipping on 2-3 upshift, flare or delayed engagement into 3rd gear, transmission slipping under load, burnt fluid smell
Fix: Aluminum bore wears where servo piston rides, causing pressure loss. Requires transmission removal and case machining or sleeve kit installation. Quality rebuild includes all clutches and bands. 8-12 hours labor.
Estimated cost: $2,200-3,500
4.0L SOHC Head Gasket Failure
Occasional · high severity
Typical onset: 100,000-180,000 mi
Symptoms: white smoke from exhaust, coolant loss with no visible leaks, overheating, rough idle and misfires, oil in coolant or vice versa
Fix: SOHC heads are prone to warping and gasket failure between cylinders or into coolant passages. Requires both heads removed, machined, new gaskets, timing components. While apart, replace chains and guides. 14-18 hours labor.
Estimated cost: $3,200-5,000
Front Lower Control Arm Bushing Deterioration
Common · low severity
Typical onset: 70,000-110,000 mi
Symptoms: clunking over bumps from front end, steering wander and poor return to center, uneven tire wear on inside edges, vibration during braking
Fix: Rubber bushings crack and separate from control arms. Replace both lower control arms with bushings pressed in (most shops replace the whole arm vs. pressing bushings). 2-3 hours labor plus alignment.
Estimated cost: $500-800
Rear Axle Pinion Seal Leak
Occasional · low severity
Typical onset: 80,000-130,000 mi
Symptoms: gear oil drips or pooling under rear differential, whining noise from rear axle when low on fluid, visible oil on rear diff cover and around pinion yoke
Fix: Pinion seal hardens and leaks. Requires driveshaft removal, pinion nut torque measurement for preload, seal replacement, and fluid refill. Critical to maintain proper preload. 2-3 hours labor.
Estimated cost: $350-550
4.6L V8 Spark Plug Ejection (Coil-On-Plug)
Occasional · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: sudden misfire and check engine light, hissing sound from engine bay, loss of power, plug found sitting on top of valve cover or dangling by wire
Fix: Aluminum head threads strip and spark plug blows out under combustion pressure. Requires helicoil or time-sert thread repair kit. Single cylinder is 2-3 hours; multiple failures common if first one ignored. Some shops remove head for proper repair.
Estimated cost: $400-700 per cylinder with time-sert; $1,500-2,500 if head removal required
Owner tips
Replace transmission cooler lines and external cooler proactively at 60k mi to avoid the 'pink milkshake' trans death
On 4.0L V6, if you hear any cold-start rattle past 80k mi, replace timing chains immediately before they jump
Change transmission fluid every 30k mi with Mercon V—5R55 is sensitive to burnt fluid
For 4.6L V8, use quality spark plugs and torque to spec—overtorquing accelerates thread failure
Avoid the 4.0L V6 unless chains and cooler lines are documented as replaced; the 4.6L V8 is more reliable but prices reflect it—budget $2k/year for deferred maintenance on any high-mileage example.
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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Every control module on the 2002-2005 Ford Explorer — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
⚠️ Odometer programming required to transfer mileage. VIN and configuration must be programmed. PATS transceiver integrated in cluster.
Air Suspension Control Module (ASCM)1.0 hr R&Rrelearn only +0.2 hrWith rear air suspension option (discontinued after 2003)▸ programming details
📍 Rear cargo area, driver side behind trim panel
🔧 Self-calibration via ride height sensors
⚠️ Controls rear air springs and compressor. Height calibration auto-learns. Compressor located under vehicle near spare tire. Option dropped mid-generation.
Audio Control Module (ACM)0.8 hr R&Rrelearn only +0.2 hr▸ programming details
📍 Behind center stack, integrated with radio head unit
🔧 Clock and presets manual reset
⚠️ Premium sound systems (Audiophile) have external amplifier under passenger seat. Some models require radio code entry after battery disconnect.
⚠️ Controls seat position memory. Memory settings stored in module; lost on replacement. No programming required but settings must be manually re-entered.
Trailer Tow Module (TTM)0.7 hr R&Rno codingWith factory trailer tow package
📍 Behind rear bumper, driver side near hitch receiver
⚠️ Provides trailer lamp diagnostics and relay control. No programming required.
⚠️ Not a separate module; function split between PCM and IC. Key programming requires IDS. Two programmed keys needed to add additional keys via self-learn procedure.
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
DOPE, INC. IS RECALLING 42,540 COMBINATION CORNER AND BUMPER LAMP ASSEMBLIES OF VARIOUS PART NUMBERS SOLD FOR USE AS AFTERMARKET EQUIPMENT FOR VARIOUS PASSENGER VEHICLES. THESE HEADLAMPS FAIL TO CONFORM TO THE REQUIREMENTS OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 108, "LAMPS, REFLECTIVE DEVICES, AND ASSOCIATED EQUIPMENT." THESE LAMPS DO NOT CONTAIN THE REQUIRED AMBER SIDE REFLECTORS.
Consequence: DECREASED LIGHTING VISIBILITY MAY RESULT IN A VEHICLE CRASH.
Remedy: DOPE, INC. WILL NOTIFY OWNERS AND OFFER A FULL REFUND FOR THE NONCOMPLIANT COMBINATION LAMPS. THE SAFETY RECALL BEGAN ON JULY 28, 2009. OWNERS MAY CONTACT DOPE, INC. AT 1-626-272-1798.
VISIBILITY:GLASS, SIDE/REAR · 07E104000
2007-12-11
CERTAIN CURVED TEMPERED REPLACEMENT GLASS MANUFACTURED BY HANGZHOU SAFETY GLASS LTD AND SUPPLIED TO SAFELITE BY AUTO TEMP INC., IDENTIFIED AS DOT-430, AND SOLD FOR USE ON CERTAIN DOMESTIC AND FOREIGN VEHICLES MAY NOT BREAK INTO SMALL PIECES AS EXPECTED OF TEMPERED GLASS AND FAILS TO CONFORM TO FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 205, "GLAZING MATERIALS."
Consequence: IN THE EVENT OF A VEHICLE CRASH, THE OCCUPANT(S) MAY BE SERIOUSLY INJURED BY SHATTERED GLASS.
Remedy: SAFELITE WILL NOTIFY ITS RETAIL CUSTOMERS AND REPLACE THE GLASS FREE OF CHARGE. RETAIL CUSTOMERS CAN CONTACT SAFELITE TOLL FREE AT 1-888-843-2906. SAFELITE WILL NOTIFY ITS WHOLESALE CUSTOMERS AND REIMBURSE WHOLESALE CUSTOMERS FOR CURRENT INVENTORY AND AT A SPECIFIED RATE FOR REPLACING THEIR CUSTOMER'S GLASS. WHOLESALE CUSTOMERS CAN CONTACT SAFELITE'S WHOLESALE DIVISION, SERVICE AUTOGLASS TOLL FREE AT 1-888-246-6298. THE RECALL BEGAN ON JANUARY 15, 2008.
EXTERIOR LIGHTING · 06E049000
2006-05-24
CERTAIN CK MOTORSPORTS COMBINATION HEADLIGHTS, CLEAR CORNER, BUMPER, AND SIDE MARKER LIGHTS SOLD AS REPLACEMENT LAMPS FOR USE ON THE PASSENGER VEHICLES LISTED ABOVE. SOME COMBINATION LAMPS THAT ARE NOT EQUIPPED WITH AMBER SIDE REFLECTORS FAIL TO CONFORM TO FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 108, LAMPS, REFLECTIVE DEVICES, AND ASSOCIATED EQUIPMENT.
Consequence: WITHOUT THE AMBER REFLECTORS, THE VEHICLE WILL BE POORLY ILLUMINATED, POSSIBLY RESULTING IN A VEHICLE CRASH WITHOUT WARNING.
Remedy: CK MOTORSPORT WILL NOTIFY OWNERS AND REPLACE THE NONCOMPLIANT LAMPS FREE OF CHARGE. THE RECALL BEGAN ON JULY 1, 2006. OWNERS MAY CONTACT CK MOTORSPORT AT 1-909-610-7211.
EXTERIOR LIGHTING · 06E026000
2006-03-23
CERTAIN PRO-A MOTORS CORNER LAMPS, TURN SIGNALS, AND HEADLIGHTS SOLD AS REPLACEMENT LAMPS FOR USE ON CERTAIN PASSENGER VEHICLES LISTED ABOVE. SOME COMBINATION LAMPS THAT ARE NOT EQUIPPED WITH AMBER SIDE REFLECTORS FAIL TO CONFORM TO FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 108, LAMPS, REFLECTIVE DEVICES, AND ASSOCIATED EQUIPMENT.
Consequence: WITHOUT THE AMBER REFLECTORS, THE VEHICLE WILL BE POORLY ILLUMINATED, POSSIBLY RESULTING IN A VEHICLE CRASH WITHOUT WARNING.
Remedy: PRO-A MOTORS WILL NOTIFY OWNERS AND OFFER TO REPURCHASE THE LAMPS. THE RECALL BEGAN ON APRIL 3, 2006. OWNERS MAY CONTACT PRO-A MOTORS AT 323-838-2988.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2004 Ford Explorer 4.6L V8 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.