2000 INFINITI Q45

Typical onset: 80,000-140,000 mi

Symptoms: Sudden knocking or rattling from lower engine, usually starts cold then worsens, Loss of compression on one or more cylinders, Metal shavings in oil, sometimes visible during oil change, Severe cases: complete piston skirt separation, hole punched through block

Fix: Factory piston skirts were too thin on many VH41DE engines, leading to cracking and ring land failure. Fix requires complete teardown and rebuild with updated pistons, rings, bearings, and often machine work. Expect 25-35 hours labor for a proper rebuild. Many owners opt for used low-mileage JDM engines (8-12 hours swap) but risk inheriting same defect.

Estimated cost: $4,500-8,500

Typical onset: 90,000-150,000 mi

Symptoms: Transmission fluid leaking from radiator area or cooler lines, Transmission overheating, especially under load or in hot weather, Harsh or delayed shifts after extended highway driving, Pink or milky fluid if cooler fails internally and mixes with coolant

Fix: The external transmission cooler and hard lines corrode and fail, or the internal radiator cooler clogs. Replace all cooler lines, external cooler, and flush transmission thoroughly. If coolant contaminated trans fluid, expect full transmission rebuild. 4-6 hours for lines and cooler, 18-24 hours if trans needs rebuild.

Estimated cost: $800-1,200 (lines/cooler only), $3,500-5,000 (with trans rebuild)

Typical onset: 70,000-120,000 mi

Symptoms: Clunk or thud when shifting from Park to Drive or Reverse, Vibration through chassis at idle in gear, Excessive driveline movement visible when engine rocks under throttle, Harsh engagement into gear

Fix: The rear transmission mount's rubber deteriorates and separates, allowing excessive driveline movement. Replacement requires supporting transmission, removing crossmember, and installing new mount. 2-3 hours labor. OEM mount recommended as aftermarket units fail prematurely.

Estimated cost: $350-550

Typical onset: 60,000-100,000 mi

Symptoms: Hesitation or stumbling under acceleration, especially uphill, Intermittent stalling at idle after spirited driving, Rough idle and poor fuel economy, Check engine light with lean codes (P0171/P0174)

Fix: In-tank fuel filter and inline filter both clog over time, especially if tank has accumulated sediment. Replace both filters as a set. In-tank requires dropping fuel tank. 3-4 hours labor. While tank is down, inspect fuel pump and sender unit for corrosion.

Estimated cost: $450-700

Typical onset: 100,000-160,000 mi

Symptoms: Oil weeping from cylinder head to block mating surface, Valve cover area appears oily but covers aren't leaking, Slow oil consumption without visible drips on ground, No coolant mixing, no overheating—strictly external seepage

Fix: VH41DE head gaskets can weep oil externally at high mileage without failing internally. If caught early and not mixing fluids, can monitor and top off. Full fix requires heads-off job: 16-20 hours labor, includes new gaskets, ARP studs recommended, valve job, and resurfacing. Only worth doing if engine is otherwise healthy (see problem #1).

Estimated cost: $2,800-4,200

Typical onset: 80,000-130,000 mi

Symptoms: Battery light intermittent or steady on dash, Voltage gauge reading low (below 13V) or erratic, Electrical accessories dimming at idle, Dead battery after short sits, battery tests good

Fix: Mitsubishi-built alternators have internal voltage regulator failures. Rebuild kits available but most shops replace entire unit. 2-3 hours labor due to tight engine bay access. Use OEM or quality reman (Bosch, Denso), cheap alternators fail within a year on this chassis.

Estimated cost: $550-850