2002 TOYOTA SIENNA

Typical onset: 90,000-150,000 mi

Symptoms: Check engine light with VVT codes (P1349, P1346), Rough idle and hesitation, Ticking or knocking from valve train, Sudden loss of oil pressure, Complete engine seizure in worst cases

Fix: The 3.0L 1MZ-FE is infamous for oil sludge buildup in the cylinder heads that starves the VVT gears and eventually destroys bearings. Once sludge is advanced, no additive or flush will save it—you're looking at either a full engine teardown with head gaskets, new VVT gears, oil pump, and cleaning (18-24 hours labor), or more commonly a used/rebuilt engine swap (12-16 hours). Many shops won't touch an internal clean on a sludged engine—too much liability—so replacement is the realistic path.

Estimated cost: $3,500-6,500

Typical onset: 100,000-180,000 mi

Symptoms: Transmission slipping or delayed engagement, Pink or milky transmission fluid, Transmission overheating, Hard shifts or shuddering

Fix: The steel cooler lines rust through where they connect to the radiator's internal ATF cooler, allowing coolant and ATF to mix. This contaminates the transmission and often destroys it within weeks if not caught early. Proper fix requires new cooler lines, external add-on cooler, complete transmission flush (sometimes a full fluid exchange machine cycle repeated 3-4 times), and often a transmission rebuild or replacement if contamination went too far (10-14 hours for full repair with rebuild). Do NOT just replace lines and top off fluid—that kills transmissions.

Estimated cost: $2,000-4,200

Typical onset: 80,000-130,000 mi

Symptoms: Clunking when shifting from Park to Drive or Reverse, Excessive vibration at idle, Visible engine/transmission movement when accelerating, Banging noise over bumps

Fix: The rear transmission mount (dogbone mount) deteriorates and separates, letting the powertrain rock excessively. It's a straightforward replacement but requires supporting the transmission and may need subframe bolts freed up if corroded. 2-3 hours labor typically.

Estimated cost: $250-450

Typical onset: 120,000-180,000 mi

Symptoms: White smoke from exhaust, Coolant loss with no visible leaks, Overheating, Milky oil on dipstick or oil cap, Rough running and misfires

Fix: The 1MZ-FE can blow head gaskets, especially if overheated or if oil sludge caused localized hot spots. Requires both heads off, machining if warped, new gaskets, timing belt, water pump while you're in there, and thorough cleaning if sludge is present. 14-18 hours labor. Often this job reveals sludge damage that makes you question doing the gaskets at all versus swapping the engine.

Estimated cost: $2,800-4,500

Typical onset: 100,000-160,000 mi

Symptoms: Hard starting, especially when hot, Loss of power under load, Sputtering or stalling at highway speeds, Check engine light with lean codes

Fix: The in-tank fuel pump strainer clogs with sediment, especially if cheap gas or old tank crud is present. Toyota didn't make this a regular service item, so many pumps wear prematurely. Requires dropping the tank, replacing pump assembly. 3-4 hours labor.

Estimated cost: $600-950

Typical onset: 60,000-120,000 mi

Symptoms: Clunk or knock felt in steering wheel when turning at low speeds, Noise from steering column area when going over bumps while turning

Fix: The universal joint in the intermediate shaft wears and develops slop. Replacement shaft with updated design fixes it. 1.5-2 hours labor. Annoying but not dangerous.

Estimated cost: $250-450