The 1998 Montero is a capable off-roader with solid mechanicals, but transmission cooling failures and V6 head gasket issues are the make-or-break concerns that define ownership cost. These aren't small repairs—budget accordingly.
Transmission Oil Cooler Failure Leading to Trans Destruction
Common · high severityTypical onset: 80,000-140,000 mi
Symptoms: Pink or milky transmission fluid (coolant mixing), Transmission slipping or delayed shifts after coolant contamination, Overheating transmission, especially when towing or climbing, Sudden catastrophic trans failure if cooler ruptures internally
Fix: The factory transmission cooler inside the radiator fails, allowing coolant and ATF to mix—this kills the transmission in days or weeks. Proper fix requires new radiator with external trans cooler bypass, full transmission flush or rebuild if contamination occurred, and all cooler lines replaced. Prevention is replacing radiator preemptively and adding external cooler. 8-15 hours labor depending on trans damage.
Estimated cost: $1,200-$4,500
Head Gasket Failure on 3.0L V6
Common · high severityTypical onset: 100,000-150,000 mi
Symptoms: White smoke from exhaust on cold start, Coolant loss with no visible leaks, Overheating under load or highway driving, Milky oil or oil in coolant reservoir, Rough idle or misfires in extreme cases
Fix: The 3.0L V6 is notorious for blown head gaskets, often both banks. Requires cylinder head removal, resurfacing, new gaskets, and timing belt replacement while you're in there. Many shops recommend new head bolts and complete coolant system refresh. 12-16 hours labor for both sides. The 3.5L is significantly better but not immune.
Estimated cost: $2,500-$4,000
Transfer Case and Transmission Mount Deterioration
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Clunking on acceleration or deceleration, Vibration at highway speeds (55-65 mph sweet spot), Difficulty shifting into gear or grinding, Visible droop or movement of transmission/transfer case
Fix: Rubber transmission and transfer case mounts fail from age and off-road use. Creates a domino effect—bad mounts stress driveshafts and U-joints. Replace all mounts as a set along with inspecting driveshaft components. 3-5 hours labor. Prevent by replacing at 100k regardless of symptoms.
Estimated cost: $400-$800
Crank Position Sensor Failure (No-Start Condition)
Occasional · high severityTypical onset: 90,000-160,000 mi
Symptoms: Sudden no-start with no warning (cranks but won't fire), Intermittent stalling when engine is hot, Engine dies while driving and won't restart until cool, No spark, no fuel pump activation
Fix: The crank position sensor fails from heat cycling and leaves you stranded—common failure point on these V6s. Sensor is buried near the bellhousing. Diagnosis is easy with scanner, replacement takes 1.5-2.5 hours due to access. Keep a spare in the glove box if you wheel it in remote areas.
Estimated cost: $200-$400
Front Axle Vacuum Disconnect System Failure
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: 4WD won't engage or intermittent engagement, Grinding or clunking when trying to engage 4WD, 4WD light flashing on dash, Hissing sound from front axle area
Fix: The vacuum-actuated front axle disconnect system uses brittle plastic lines and diaphragms that crack and leak. Many owners eliminate the system entirely with manual conversion kit or free-spin hub swap. Factory fix requires replacing vacuum lines, check valve, and actuator. 2-4 hours for OEM repair, 3-5 for manual conversion.
Estimated cost: $300-$800
Fuel Pump and Sending Unit Failure
Occasional · medium severityTypical onset: 100,000-180,000 mi
Symptoms: Hard starting after sitting, especially in heat, Sputtering or dying at low fuel levels (below 1/4 tank), Inaccurate fuel gauge or erratic needle movement, Loss of power under acceleration or uphill
Fix: The in-tank fuel pump and sending unit assemblies fail from age and ethanol fuel degradation. Requires fuel tank drop, which is labor-intensive on this chassis. Replace pump, strainer, and sending unit as complete assembly. 3-4 hours labor. Use OEM or quality aftermarket—cheap pumps fail quickly.
Estimated cost: $500-$900
Buy a 3.5L model with documented trans cooler bypass and head gasket history—otherwise you're inheriting $4k-6k in deferred maintenance, but a well-maintained example is bulletproof and vastly more capable than modern crossovers.
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.