The 2024 Sienna is still very new to the market, but early patterns mirror issues seen in the 2021-2023 hybrid models. The hybrid powertrain is generally solid, but transmission oil cooler failures and engine oil consumption problems are emerging as the primary concerns.
Transmission Oil Cooler Failure
Occasional · high severityTypical onset: 40,000-80,000 mi
Symptoms: Transmission fluid leaking into coolant or vice versa (milky fluid in either system), Transmission slipping or harsh shifts, Engine overheating, Check engine light with transmission temperature codes
Fix: Replace transmission oil cooler, flush both cooling system and transmission. Requires partial transmission disassembly and coolant system purge. 4-6 hours labor plus parts.
Estimated cost: $1,200-2,000
Excessive Oil Consumption / Piston Ring Failure
Occasional · high severityTypical onset: 30,000-70,000 mi
Symptoms: Burning a quart of oil every 1,000-2,000 miles, Blue smoke from exhaust on startup or acceleration, Fouled spark plugs, Low oil warning light despite recent oil change
Fix: Toyota has a pattern of oil consumption issues on some A25A-FXS engines. Repair requires engine teardown to replace piston rings or full short block replacement in severe cases. 18-24 hours labor for short block swap.
Estimated cost: $5,000-8,500
Transmission Mount Failure
Common · medium severityTypical onset: 50,000-90,000 mi
Symptoms: Clunking noise when shifting from park to drive or reverse, Excessive vibration at idle, Visible sagging or torn rubber on mount inspection
Fix: Replace failed transmission mount. The hybrid CVT and electric motor assembly is heavy, causing accelerated wear. 2-3 hours labor.
Estimated cost: $400-700
Fuel System Contamination / Fuel Filter Clogging
Rare · medium severitySymptoms: Hard starting or extended cranking, Loss of power under acceleration, Check engine light with fuel pressure or lean codes, Rough idle
Fix: Related to fuel tank manufacturing debris or poor fuel quality. Requires fuel filter replacement and sometimes fuel system cleaning or tank drop. 2-4 hours depending on contamination extent.
Estimated cost: $300-900
Hybrid System Inverter Cooling Issues
Rare · high severityTypical onset: 60,000-100,000 mi
Symptoms: Hybrid system warning light, Reduced power mode, Intermittent loss of electric motor assist, Overheating warnings in hot weather or under load
Fix: Inverter cooling pump or coolant passages can fail. Requires diagnosis with Toyota Techstream scanner, replacement of cooling pump or inverter assembly. 3-6 hours labor.
Estimated cost: $1,500-3,500
Wait another year for the oil consumption and transmission cooler issues to shake out—the 2025+ models should have these addressed under warranty campaigns.
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.