The 2015 Cayenne S with the 4.8L V8 (M48.02) is a capable luxury SUV, but it's known for catastrophic engine failures due to cylinder scoring and the cooling-system-related IMS bearing issues are gone, replaced by direct injection carbon buildup and aggressive transmission oil cooler failures that can cross-contaminate fluids.
Cylinder Bore Scoring / Engine Failure
Occasional · high severityTypical onset: 60,000-100,000 mi
Symptoms: Excessive oil consumption (more than 1 quart per 1,000 miles), Cold-start smoke from exhaust (blue-gray), Loss of compression, rough idle, misfires, Metallic noise from crankcase
Fix: Requires complete engine rebuild or short block replacement. 40-60 hours labor for R&R and rebuild with new Lokasil-coated cylinders, pistons, rings, bearings. Some shops opt for used low-mileage engine swap to save cost.
Estimated cost: $15,000-25,000
Transmission Oil Cooler Failure / Cross-Contamination
Common · high severityTypical onset: 70,000-110,000 mi
Symptoms: Transmission fluid in coolant expansion tank (milky pink coolant), Coolant in transmission pan (strawberry milkshake fluid), Harsh shifting or slipping after overheating, Check engine light with transmission fault codes
Fix: Replace transmission oil cooler, flush both cooling system and transmission multiple times, replace thermostat and coolant hoses. If contamination was severe, transmission may need rebuild. 8-12 hours for cooler and flushes, add 20-30 hours if trans needs rebuild.
Estimated cost: $2,500-4,500 (cooler only), $8,000-12,000 (with trans rebuild)
Direct Injection Carbon Buildup
Common · medium severityTypical onset: 50,000-80,000 mi
Symptoms: Rough idle, especially when cold, Misfires on one or more cylinders (P0300-P0308), Loss of power on acceleration, Increased fuel consumption
Fix: Walnut-blast cleaning of intake valves. Remove intake manifold, mask ports, blast each valve with crushed walnut media, vacuum out debris. 6-8 hours labor. Should be done every 50-60k miles as preventive maintenance on direct-injection engines.
Estimated cost: $800-1,400
Coolant Pipe / Crossover Pipe Leaks
Common · medium severityTypical onset: 80,000-120,000 mi
Symptoms: Coolant smell in cabin or under hood, Visible coolant leak at rear of engine (valley area), Low coolant warning light, Overheating if leak is severe
Fix: Replace plastic coolant crossover pipes in the valley between cylinder banks. Requires removing intake manifold and accessory components for access. Upgrade to updated revision pipes. 8-10 hours labor.
Estimated cost: $1,800-2,800
Transfer Case Actuator Motor Failure
Occasional · medium severityTypical onset: 90,000-130,000 mi
Symptoms: Transfer case fault warning on dash, Stuck in 2WD or AWD mode, Grinding or clicking noise from transfer case area, Inability to shift between drive modes
Fix: Replace transfer case actuator motor (shift motor). Requires raising vehicle, removing skid plates, and accessing actuator on transfer case. Motor replacement only, no case disassembly needed. 3-4 hours labor.
Estimated cost: $1,200-1,800
Engine/Transmission Mounts Deterioration
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: Clunk or thud when shifting from Park to Drive, Excessive vibration at idle, Engine movement visible during acceleration/deceleration, Driveline shudder during hard throttle
Fix: Replace worn hydraulic engine mounts and transmission mount. Typically front and rear engine mounts plus trans mount as a set. Requires supporting engine/trans with jack during replacement. 4-6 hours labor for all three.
Estimated cost: $1,500-2,200
Fantastic to drive but a financial gamble—only buy with impeccable service records, proof of preventive carbon cleaning, and a borescope-verified healthy engine, or budget $20k for worst-case engine replacement.
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.