The 2000 LHS shares the LH platform with the 300M and Concorde, pairing a generally reliable 3.5L V6 with the Achilles heel 42LE four-speed automatic transmission. Engine longevity is good if maintained, but transmission failures and secondary cooling system issues define ownership cost after 100k miles.
42LE Transmission Failure (Complete Internal Destruction)
Common · high severityTypical onset: 80,000-140,000 mi
Symptoms: Slipping between gears, especially 2nd-3rd shift, Delayed engagement when shifting from Park to Drive, Harsh downshifts or banging into gear, Metal shavings in pan, burnt fluid smell, Check Engine light with solenoid/pressure codes
Fix: Rebuild or replace transmission. Rebuild takes 8-12 hours and often fails again within 50k if not done by a specialist. Remanufactured unit is the safer bet. Many shops won't touch these anymore—limited parts availability and poor rebuild success rate.
Estimated cost: $2,200-3,800
Transmission Oil Cooler Line Corrosion and Leaks
Common · medium severityTypical onset: 90,000-150,000 mi
Symptoms: Transmission fluid puddles under front of vehicle, Visible rust and perforation on steel cooler lines near radiator, Low fluid level leading to slipping/overheating, Pink or red fluid mixing with coolant if internal radiator cooler fails
Fix: Replace corroded steel lines with new or aftermarket stainless. If radiator-mounted cooler is leaking internally (the 'pink milkshake'), you must flush transmission immediately and replace radiator. 2-3 hours labor for lines only, 4-5 if radiator involved.
Estimated cost: $350-900
Crankshaft Position Sensor Failure (No-Start Condition)
Occasional · high severityTypical onset: 70,000-120,000 mi
Symptoms: Intermittent stalling while driving, usually restarts after cooling, Crank no-start with no spark or fuel pump activation, P0320 or P0340 codes (crank/cam sensor circuit), Tachometer drops to zero while cranking
Fix: Replace crankshaft position sensor mounted on transmission bellhousing. Access requires raising vehicle and working from underneath. Common failure point on 3.5L engines. 1-1.5 hours labor, inexpensive part.
Estimated cost: $180-300
Engine Sludge Formation (Poor Maintenance History)
Occasional · high severityTypical onset: 100,000+ mi
Symptoms: Valve train noise (ticking/tapping) at startup, Low oil pressure warning light, especially when hot, Excessive oil consumption between changes, Visible black sludge in valve covers or oil filler neck
Fix: If caught early, aggressive flushing and short-interval oil changes (every 2,000 mi) may save it. Advanced cases need complete teardown: head removal, oil pan drop, pickup screen cleaning, possibly full rebuild. The 3.5L is susceptible if neglected or run on cheap conventional oil past 5k intervals. Prevention is everything here. Rebuild is 18-25 hours.
Estimated cost: $3,500-6,500
Water Pump and Timing Belt Failure
Common · high severityTypical onset: 90,000-110,000 mi
Symptoms: Coolant leak from front of engine, Squealing or grinding noise from timing cover area, Engine overheating, Catastrophic engine damage if belt breaks (interference engine)
Fix: This is an interference engine—timing belt failure destroys valves and pistons. Belt, water pump, tensioners, and seals must be done together as preventive maintenance at 100k or 7 years, whichever comes first. Non-negotiable. 4-6 hours labor for the complete job.
Estimated cost: $650-1,100
Front Transmission Mount Collapse
Common · low severityTypical onset: 80,000-130,000 mi
Symptoms: Excessive engine movement visible when shifting between Drive and Reverse, Clunking from engine bay during acceleration or deceleration, Vibration felt through steering wheel and floor at idle, Misalignment causing accelerated CV axle wear
Fix: Upper transmission mount (dogbone mount) deteriorates from heat and stress. Replacement is straightforward but requires supporting powertrain. Often done alongside lower mounts for best results. 1.5-2 hours labor.
Estimated cost: $220-380
Alternator Failure with Voltage Regulator Issues
Occasional · medium severityTypical onset: 90,000-140,000 mi
Symptoms: Battery light illuminated or flickering, Dimming headlights at idle, brightening with RPM, Electrical accessories acting erratically, Battery repeatedly dying or overcharging (bulging case), Voltage gauge showing below 13V or above 15V
Fix: Alternator replacement on 3.5L requires removing serpentine belt and working around tight engine bay. Original Nippondenso units last well; cheap replacements often fail within a year. 1.5-2 hours labor.
Estimated cost: $350-550
Buy only if transmission has already been replaced or rebuilt by a reputable shop with warranty, timing belt is documented fresh, and you have $2-3k set aside for the inevitable next transmission issue—otherwise walk away.
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.