The 1991 Q45 was Infiniti's flagship with a brilliant 4.5L V8, but suffers from predictable failure patterns around the cooling system, transmission cooling, aging rubber mounts, and occasionally catastrophic internal engine wear if maintenance was deferred.
Transmission Oil Cooler Line Failure and Cooler Leaks
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: transmission fluid pooling under vehicle, pink fluid dripping from radiator area, transmission overheating or slipping, burnt transmission smell
Fix: Replace transmission cooler lines (they corrode where they pass through subframe) and often the radiator-mounted cooler itself. 3-5 hours labor depending on whether radiator comes out. Flush transmission thoroughly after repair to prevent damage from contaminated fluid.
Estimated cost: $600-1,200
Engine Rebuild Due to Piston Ring and Bearing Wear
Occasional · high severityTypical onset: 120,000-180,000 mi
Symptoms: excessive oil consumption (quart per 500-1000 miles), blue smoke on startup or acceleration, rod knock or main bearing noise, loss of compression, metal shavings in oil
Fix: VH45DE engines with poor maintenance history develop worn rings, scored cylinders, and bearing failure. Full rebuild includes pistons, rings, bearings, head gaskets, timing components, seals. 35-50 hours labor for complete tear-down and rebuild. Some opt for used JDM engines instead at 20-25 hours swap time.
Estimated cost: $4,500-8,000
Collapsed or Torn Engine and Transmission Mounts
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: clunking on acceleration or deceleration, excessive vibration at idle, visible engine movement when revving in park, shifter vibration
Fix: Hydraulic mounts fail internally; rubber tears or fluid leaks out. Front engine mount and transmission mount are most common. Replace all mounts as a set for best results. 4-6 hours labor for all four mounts.
Estimated cost: $800-1,400
Head Gasket Failure (Both Banks)
Occasional · high severityTypical onset: 90,000-140,000 mi
Symptoms: coolant loss with no external leaks, white exhaust smoke, overheating, milky oil, bubbles in coolant reservoir
Fix: VH45DE head gaskets fail between coolant and oil passages or into cylinders, often due to overheating history. Must do both banks. Resurface heads, replace timing components while open. 18-24 hours labor.
Estimated cost: $2,800-4,200
Fuel Filter Clogging and Fuel Pump Wear
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: hard starting when hot, stumbling under acceleration, loss of power above 3500 RPM, rough idle, stalling
Fix: In-tank fuel pump strainers clog, pumps wear out. External inline filter also clogs if never changed. Replace pump assembly and both filters together. Tank must be dropped. 4-5 hours labor.
Estimated cost: $650-1,100
Front Lower Control Arm Bushing Deterioration
Common · low severityTypical onset: 80,000-130,000 mi
Symptoms: clunking over bumps, steering wander, uneven tire wear on inside edges, vibration at highway speed
Fix: Rubber bushings crack and tear. Replace complete control arms with new bushings pressed in (easier than pressing bushings separately). Alignment required. 3-4 hours labor both sides.
Estimated cost: $700-1,100
Alternator Failure
Occasional · medium severityTypical onset: 90,000-150,000 mi
Symptoms: battery light on, dimming lights, electrical accessories cutting out, battery repeatedly dying, whining noise from alternator area
Fix: 110-amp alternator fails due to worn brushes or regulator. Replacement is straightforward on this engine. 1.5-2 hours labor. Use quality rebuilt unit.
Estimated cost: $400-650
Fantastic highway cruiser if maintained properly, but a well-documented service history is mandatory—deferred maintenance turns expensive fast on the VH45DE engine.
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.