The 2020 Honda S660 is a Japan-domestic kei sports car with a mid-mounted 0.66L turbocharged three-cylinder. While charming and generally reliable by Honda standards, the small-displacement turbo engine runs hard and the CVT transmission requires careful maintenance—abuse or neglect accelerates wear significantly.
CVT Transmission Judder and Premature Wear
Common · medium severityTypical onset: 40,000-70,000 mi
Symptoms: Shuddering or hesitation during acceleration from a stop, Whining or grinding noises under load, Delayed engagement when shifting from Park to Drive, CVT fluid darkening or burnt smell earlier than service interval
Fix: CVT fluid and filter change often improves early symptoms (2.0 hours). Advanced cases need transmission overhaul or replacement unit (12-16 hours). Aggressive driving or towing (even light loads) kills these CVTs faster than normal kei-car use.
Estimated cost: $400-800 fluid service, $3,500-5,500 overhaul/replacement
Timing Chain Stretch and Tensioner Failure
Occasional · high severityTypical onset: 60,000-90,000 mi
Symptoms: Rattling noise on cold start that fades after 10-15 seconds, Check engine light with cam/crank correlation codes (P0016, P0017), Rough idle or hesitation at low RPM, Metallic ticking that worsens with RPM
Fix: Timing chain, guides, and tensioner replacement requires significant disassembly in the mid-engine bay (8-11 hours). Catch it early—if the chain jumps timing, valve-to-piston contact destroys the engine. Common on engines that see frequent high-RPM use or extended oil change intervals.
Estimated cost: $2,200-3,800
Valve Lifter Noise and Premature Wear
Common · medium severityTypical onset: 50,000-80,000 mi
Symptoms: Ticking or tapping from cylinder head, worse when cold, Noise persists or worsens after oil changes, Slight loss of power or throttle response at high RPM, Oil consumption increases gradually
Fix: Hydraulic lifters collapse due to oil quality issues or sustained high-RPM abuse. Replacing all lifters requires cylinder head removal (9-12 hours). Some techs attempt an engine flush and premium oil first (success rate ~30%). Head resurfacing often needed if caught late.
Estimated cost: $1,800-3,200 lifters only, $3,000-4,500 with head work
Transmission Oil Cooler Leaks
Occasional · medium severityTypical onset: 50,000-90,000 mi
Symptoms: CVT fluid drips or puddles under the engine bay, Transmission temperature warning light (rare, but possible), Burnt CVT fluid smell after spirited driving, Low fluid level on dipstick check
Fix: Small auxiliary cooler and lines corrode or crack from road salt and heat cycling. Replacement is straightforward (2-3 hours) but requires proper CVT fluid refill and air purge. Ignore it and you'll cook the CVT.
Estimated cost: $600-1,200
Harmonic Balancer Deterioration
Rare · high severityTypical onset: 70,000-100,000 mi
Symptoms: Vibration felt through chassis at idle or specific RPM ranges, Visible wobble on the crankshaft pulley during running, Squealing or chirping from accessory belt area, Rubber layer separating from pulley hub
Fix: The small three-cylinder's inherent imbalance stresses the balancer. When the rubber bond fails, it can grenade and take the accessory belt and timing components with it. Replacement requires front engine cover removal (4-5 hours). Inspect every 30k if driven hard.
Estimated cost: $800-1,400
Turbocharger Wastegate Rattle
Occasional · low severityTypical onset: 60,000-100,000 mi
Symptoms: Metallic rattling noise at idle, disappears under boost, Slight loss of boost pressure or sluggish acceleration, P0299 code (turbo underboost) in severe cases
Fix: Wastegate actuator rod or flapper develops play from heat cycling. Many owners live with the rattle; if boost control is affected, wastegate actuator replacement or turbo rebuild is needed (5-7 hours for turbo R&R).
Estimated cost: $1,200-2,200 actuator, $2,500-3,800 turbo rebuild
Buy one if you can verify CVT and timing chain health and commit to aggressive fluid maintenance—neglected examples are money pits, but cared-for S660s are delightful and scrappy.
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.