The 2015 LS 460 is generally reliable, but the 4.6L V8 has a known carbon buildup issue that can escalate to catastrophic engine failure if ignored. Transmission cooling system leaks are also noteworthy on higher-mileage examples.
Carbon Buildup Leading to Engine Knock and Failure
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Cold-start engine knock or rattle that disappears when warm, Reduced power and fuel economy, Check engine light with lean codes or misfire codes, Catastrophic failure: spun bearings, damaged pistons, scored cylinder walls
Fix: Early stage: walnut blasting intake valves and decarb service (4-6 hours labor). Advanced stage with internal damage requires full engine rebuild or short block replacement (25-35 hours labor). This V8 uses direct injection only, so intake valves get heavy carbon deposits that break loose and score cylinder walls or cause detonation damage.
Estimated cost: $800-1,500 for decarb service; $12,000-18,000 for engine rebuild/short block
Transmission Oil Cooler Line Leaks
Occasional · medium severityTypical onset: 100,000-140,000 mi
Symptoms: Transmission fluid dripping from front of vehicle or onto exhaust, Low transmission fluid warning on dash, Burnt smell from fluid on hot components, Delayed or harsh shifts if fluid level drops significantly
Fix: Replace transmission oil cooler lines and inspect external cooler for leaks. The steel lines rust at junctions or flex points. Requires removing undercovers and draining transmission. 3-4 hours labor plus fluid refill and system flush.
Estimated cost: $600-1,200
Transmission Mount Failure
Occasional · low severityTypical onset: 90,000-130,000 mi
Symptoms: Clunk or thud when shifting from Park to Drive or Reverse, Vibration at idle in Drive with foot on brake, Excessive driveline movement visible when rocking vehicle
Fix: Replace rear transmission mount. The hydraulic mount deteriorates and allows excessive drivetrain movement. Requires supporting transmission and removing crossmember. 2-3 hours labor.
Estimated cost: $400-700
Fuel Pump and Filter Assembly Failure
Occasional · medium severityTypical onset: 120,000-160,000 mi
Symptoms: Extended cranking before engine starts, especially when hot, Intermittent stalling or hesitation under acceleration, Fuel pump whine audible from rear seat area, Check engine light with fuel trim or pressure codes
Fix: Replace in-tank fuel pump assembly including integrated filter (not separately serviceable). Requires dropping fuel tank or removing rear seat and access panel depending on access method chosen. 3-4 hours labor.
Estimated cost: $800-1,400
Water Pump Bearing Failure
Rare · high severityTypical onset: 100,000-140,000 mi
Symptoms: Grinding or squealing noise from front of engine, Coolant leak from water pump weep hole, Overheating if pump fails completely, Belt-driven accessory noise that increases with RPM
Fix: Replace water pump, timing belt, and all tensioners/idlers as assembly. This is a timing belt engine, so water pump access requires full timing service. 8-10 hours labor if done preventively; add diagnostics and potential head gasket work if overheated.
Estimated cost: $1,800-2,800 preventive; $5,000+ if overheated
Buy one under 80,000 miles with documented decarb service and full maintenance records; avoid high-mileage examples with cold-start knock, as engine damage may already be present.
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.