The 2000 Mitsubishi Diamante with the 3.5L V6 is a comfortable front-wheel-drive sedan plagued by catastrophic engine failure and transmission cooling problems. When the engine hasn't grenaded itself, it's a decent highway cruiser, but the odds aren't in your favor past 100k miles.
Catastrophic Engine Bearing Failure (6G74 V6)
Common · high severityTypical onset: 80,000-140,000 mi
Symptoms: Metallic knocking from engine at idle or acceleration, Sudden loss of oil pressure, Check engine light with low oil pressure code, Engine seizes without warning in severe cases
Fix: The 6G74 V6 has notorious oiling problems that starve the main and rod bearings, especially cylinders 1 and 6. Oil sludge buildup restricts passages even with regular changes. Requires complete engine rebuild with new bearings, rods, and pistons, or short block replacement. 18-24 labor hours for removal, rebuild, and reinstallation. Many shops won't rebuild these—they go straight to junkyard replacement.
Estimated cost: $3,500-6,500
Transmission Oil Cooler Line Failure and Fluid Contamination
Common · high severityTypical onset: 90,000-150,000 mi
Symptoms: Pink milky transmission fluid (coolant contamination), Transmission slipping or delayed engagement, Overheating transmission, External coolant leaks near radiator
Fix: The cooler lines corrode internally and externally, and the internal radiator transmission cooler can rupture, allowing coolant into the transmission. Once coolant mixes with ATF, the transmission is typically toast. Requires transmission rebuild or replacement, new radiator, all cooler lines, and complete flush. If caught early (just external line leak), replace all cooler lines and add external cooler. 12-16 hours for full transmission job.
Estimated cost: $2,800-4,800
Head Gasket Failure (Both Banks)
Occasional · high severityTypical onset: 110,000-160,000 mi
Symptoms: White smoke from exhaust, Coolant loss with no external leaks, Overheating under load, Rough idle and misfires, Oil contaminated with coolant (chocolate milkshake appearance)
Fix: The 6G74's multi-layer steel head gaskets fail between the coolant passages and combustion chambers, or externally. Both heads should be done simultaneously and resurfaced. While you're in there, timing belt, water pump, and valve cover gaskets get replaced. 14-18 labor hours for both sides.
Estimated cost: $2,200-3,800
Transmission Mount Collapse
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Severe clunk when shifting from park to drive or reverse, Excessive engine movement visible from engine bay, Vibration at idle in gear, Harsh acceleration jolt
Fix: The front and rear transmission mounts deteriorate and separate, allowing the transverse V6 and transmission assembly to rock excessively. The front mount is particularly prone to hydraulic fluid leakage and rubber separation. Replace both mounts as a pair. 2-3 labor hours.
Estimated cost: $350-650
Fuel Filter Clogging and Fuel Pump Wear
Occasional · medium severityTypical onset: 100,000-140,000 mi
Symptoms: Hard starting when engine is hot, Loss of power under acceleration, Engine stumbling or hesitation at highway speeds, Stalling in hot weather
Fix: The in-tank fuel pump and inline fuel filter see premature wear, especially if the filter wasn't changed at 60k intervals (which most owners skip). Pump strainer gets clogged with tank sediment. Replace fuel filter first (1.5 hours), then pump if symptoms persist (3-4 hours for tank drop and pump replacement).
Estimated cost: $400-900
Crankshaft Position Sensor Failure
Occasional · high severityTypical onset: 80,000-130,000 mi
Symptoms: No-start condition with cranking but no spark, Intermittent stalling while driving, Check engine light with P0320 or P0335 code, Engine cuts out suddenly then restarts after cooling
Fix: The crank sensor on the back of the engine (bellhousing area) fails due to heat cycling. When it dies, the engine won't start or will stall unexpectedly. Requires removing the intake manifold for access on this transverse setup. 3-4 labor hours.
Estimated cost: $450-750
Hard pass unless you're getting it free—the engine and transmission time bombs make this a losing proposition for anyone without a spare drivetrain on standby.
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.