The 2000 NB Miata (1.8L) is mechanically solid but suffers from a notorious crankshaft nose issue and typical transmission mount failures. The engine itself is durable if maintained, but catastrophic crank keyway failures can destroy the motor without warning.
Crankshaft Keyway Failure (Woodruff Key Shear)
Occasional · high severityTypical onset: 80,000-150,000 mi
Symptoms: sudden loss of power, rough idle or no-start after the key shears, timing off despite good belt condition, metallic noise from front of engine
Fix: The Woodruff key that locates the crank pulley can shear, letting the pulley spin freely and destroying timing. Requires crank removal, keyway repair or replacement crank, often short block if debris circulated. 15-25 hours labor for short block swap.
Estimated cost: $3,500-6,000
Transmission Mount Collapse
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: clunking on shifts, especially 1st to 2nd, excessive shifter vibration, visible sag or torn rubber on PPF mount, driveline lash on throttle tip-in
Fix: The power plant frame (PPF) mount deteriorates and causes driveline slop. Aftermarket mounts are stiffer and last longer. 1.5-2 hours labor for PPF mount replacement.
Estimated cost: $200-400
Cam Position Sensor (CAS) O-Ring Leak
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: oil seeping from back of valve cover onto firewall, rough idle or stalling when hot, check engine light with cam/crank correlation codes, oil smell in cabin with heat on
Fix: The CAS at the rear of the head uses an O-ring that hardens and leaks. Easy fix but requires intake manifold removal for access. 2-3 hours labor, replace O-ring and reseal.
Estimated cost: $250-450
Rear Main Seal Leak
Occasional · medium severityTypical onset: 100,000-150,000 mi
Symptoms: oil spots under the bell housing area, clutch contamination causing slip or chatter, visible wetness between engine and transmission, oil consumption without external leaks elsewhere
Fix: Rear main seal weeps and can soak the clutch. Requires transmission removal. Often done during clutch jobs. 6-8 hours labor if doing seal only, add 2 hours if bundling with clutch.
Estimated cost: $800-1,200
Short Nose Crank Pulley Bolt Loosening
Occasional · high severitySymptoms: harmonic squealing or wobble at idle, vibration felt through chassis, pulley visibly off-center or wobbling, check engine light with crank position codes
Fix: Early 1.8L short-nose cranks can have the main pulley bolt back out if not properly torqued or if Loctite fails. Catch it early: retorque with Loctite and fresh bolt. If it wobbles too long, keyway damage occurs—see crank failure above. Preventive retorque: 1 hour labor.
Estimated cost: $100-200
Valve Cover Gasket and Spark Plug Tube Seals
Common · low severityTypical onset: 80,000-130,000 mi
Symptoms: oil pooling in spark plug wells, burning oil smell, ignition misfire on one or more cylinders, oil weeping down side of engine
Fix: Gasket and tube seals harden over time. Straightforward job: replace gasket, tube seals, and half-moon seals. 2-3 hours labor.
Estimated cost: $300-500
Transmission Oil Cooler Line Leaks
Occasional · medium severityTypical onset: 90,000-140,000 mi
Symptoms: gear oil dripping near front crossmember, low transmission fluid causing hard shifts, visible wet lines running to small cooler behind bumper, burnt gear oil smell
Fix: Steel lines rust through or rubber sections crack. Replace lines and top off fluid. 1.5-2 hours labor, parts are inexpensive but fiddly to route.
Estimated cost: $200-350
Buy it if the crank pulley is tight and no oil leaks are present—mechanically stout and cheap to maintain, but budget for a short block if the crank has been neglected.
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.