The 2001 RX 300 is generally reliable but suffers from catastrophic transmission oil cooler failures and engine oil sludging issues that can destroy the 1MZ-FE V6. When maintained religiously, it's solid; when neglected, it's expensive scrap.
Transmission Oil Cooler Line Failure (Internal to Radiator)
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Pink or milky fluid in transmission dipstick (coolant mixing with ATF), Transmission slipping or delayed engagement, Strawberry milkshake appearance in coolant overflow, Sudden transmission failure after coolant contamination
Fix: Replace radiator with external transmission cooler setup, flush transmission multiple times, often requires transmission rebuild or replacement if contamination went unnoticed. 8-12 hours labor for full job including trans R&R if damaged.
Estimated cost: $2,500-5,500
Engine Oil Sludge (1MZ-FE V6)
Common · high severityTypical onset: 90,000-140,000 mi
Symptoms: Check engine light with VVT codes (P1349, P1346), Valve train noise on cold start, Oil pressure warning light, Rough idle and reduced power, Catastrophic engine failure if oil starvation occurs
Fix: If caught early, aggressive flush treatments may help. Advanced cases require complete teardown, head gasket replacement, new pistons/rings, bearings, and oil pump. 25-35 hours for proper engine rebuild.
Estimated cost: $4,500-7,500
Lower Engine Mount (Rear) Failure
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Clunking when shifting from Park to Drive or Reverse, Excessive engine movement visible from engine bay, Vibration through chassis during acceleration, Metallic knock during hard throttle
Fix: Replace rear transmission mount, often do front engine mount at same time as preventive. 2-3 hours labor, straightforward job but requires supporting engine/trans.
Estimated cost: $400-700
Valve Cover Gasket Leaks
Common · low severityTypical onset: 80,000-130,000 mi
Symptoms: Burning oil smell from engine bay, Oil visible on valve covers or spark plug tubes, Oil-soaked spark plug wells causing misfires, Minor oil drips on driveway
Fix: Replace both valve cover gaskets and spark plug tube seals. Access is tight, especially rear bank. 4-5 hours labor. Do spark plugs at same time.
Estimated cost: $600-1,000
Oxygen Sensor Failures (Bank 1 Sensor 2)
Occasional · low severityTypical onset: 100,000-150,000 mi
Symptoms: Check engine light P0141 or P0138, Slight decrease in fuel economy, Failed emissions test
Fix: Replace downstream O2 sensor, bank 1 (front) is easier access than bank 2 (rear). 0.5-1.0 hour labor each.
Estimated cost: $250-400
Power Steering Rack Leaks
Occasional · medium severityTypical onset: 120,000-180,000 mi
Symptoms: Power steering fluid leaking onto subframe, Groaning noise when turning at low speed, Requiring frequent PS fluid top-offs, Tight or notchy steering feel
Fix: Replace steering rack assembly, requires subframe drop for proper access. 6-8 hours labor, alignment required after.
Estimated cost: $1,200-2,000
Rear Differential Fluid Leak
Occasional · low severityTypical onset: 100,000+ mi
Symptoms: Drips or puddles under rear of vehicle, Whining noise from rear on acceleration (if run low), Visible fluid seepage at pinion seal or axle seals
Fix: Replace pinion seal or axle seals as needed. Pinion seal requires driveshaft removal and pinion nut torque setup. 2-3 hours labor.
Estimated cost: $350-600
Buy only with full service records proving frequent oil changes and recent radiator replacement; otherwise it's a $5k repair gamble waiting to happen.
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.