The 2018 Peugeot 308 with the 1.6L THP (Prince/EP6) engine is a competent European compact hampered by well-documented powertrain weaknesses—timing chain wear, carbon buildup, and fragile automatic transmission components that can turn expensive quickly if ignored.
1.6L THP Timing Chain Stretch and Failure
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: Rattling on cold start, especially first 10-15 seconds, Check engine light with cam/crank correlation codes (P0016, P0017), Rough idle and hesitation under acceleration, Metal fragments in oil during changes
Fix: Replace timing chain, tensioner, guides, and often VVT solenoids; requires front-end disassembly. 8-12 hours labor depending on additional damage. Failure to address early can grenade the engine requiring full replacement (25+ hours).
Estimated cost: $1,800-3,200
Carbon Buildup on Intake Valves (Direct Injection)
Common · medium severityTypical onset: 50,000-80,000 mi
Symptoms: Rough idle and misfires, especially when cold, Loss of power and sluggish throttle response, Increased fuel consumption, Check engine light with misfire codes (P0300-P0304)
Fix: Walnut blasting intake valves through removed intake manifold. 4-6 hours labor. Direct injection engines with no port injection get heavy carbon deposits that restrict airflow.
Estimated cost: $600-1,000
EAT6 Automatic Transmission Shuddering and Slipping
Common · high severityTypical onset: 70,000-120,000 mi
Symptoms: Shuddering or jerking during 2-3 or 3-4 upshifts, Hesitation or flare between gears under light throttle, Transmission overheating warnings on dash, Clunking when shifting into reverse
Fix: Early cases respond to fluid and filter change (3 hours), but worn clutch packs require rebuild or replacement. Oil cooler failure often contaminates fluid and accelerates wear. Full rebuild: 18-24 hours; used replacement: 12-16 hours.
Estimated cost: $800-1,200 fluid service; $3,500-5,500 rebuild
Transmission Oil Cooler Leaks and Contamination
Occasional · high severityTypical onset: 80,000-110,000 mi
Symptoms: Transmission fluid in coolant reservoir (milky or pink coolant), Transmission slipping or delayed engagement after cooler failure, Coolant leaks near transmission area, Sudden transmission overheating
Fix: Replace transmission oil cooler and flush both cooling system and transmission. If coolant entered trans, full rebuild often required. Cooler replacement alone: 3-4 hours; with trans rebuild: add 18-22 hours.
Estimated cost: $600-900 cooler only; $4,000-6,000 with contamination damage
Turbocharger Wastegate Rattle and Failure
Occasional · medium severityTypical onset: 90,000-130,000 mi
Symptoms: Rattling noise from engine bay at idle or light throttle, Loss of boost pressure and reduced power, Check engine light with underboost codes (P0299), Excessive black smoke under acceleration
Fix: Replace turbocharger assembly; wastegate arms seize or rattle loose on these units. 5-7 hours labor including coolant/oil line work and heat shield removal.
Estimated cost: $1,400-2,200
LED Headlight Module Failures
Occasional · low severitySymptoms: One or both headlights flickering or completely out, Dash warning for headlight malfunction, Intermittent operation—works when cool, fails when hot, Moisture visible inside headlight housing
Fix: Replace LED module or entire headlight assembly depending on design; Peugeot often doesn't sell modules separately. 1-2 hours per side labor.
Estimated cost: $800-1,500 per side for assembly
Engine Bay Fuse Box Water Intrusion
Occasional · medium severitySymptoms: Multiple electrical gremlins—wipers, windows, lights acting up, Corrosion visible on fuse box terminals, Intermittent no-start or crank-no-start, Water pooling in fuse box area after rain or car wash
Fix: Reseal fuse box housing, replace corroded fuses/relays, clean terminals. Some cases need full fuse box replacement. 2-4 hours labor depending on corrosion extent.
Estimated cost: $300-800
Buy only with documented timing chain replacement and recent transmission service, or budget $3-5k for inevitable powertrain work—good drive when healthy, but expensive when it's not.
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.