BMW i8 I12

The B38B15 is BMW's modular three-cylinder turbo — 1.5 liters, lively character despite only three pots. Design-inherent vibrations are normal, not a defect. Timing chain is a real concern on 2014–2018 builds (Gen1) — early failures from 50,000 km documented, significantly improved from 2019. Crankshaft pilot bearing was undersized on manual transmission cars before April 2015 — BMW quietly revised it. Plastic thermostat housing cracks, water pump is a classic BMW wear item. Reliable daily driver with proper maintenance, compression loss threatens with neglect.

• !! Timing chain elongation from 70,000 km

  Same timing chain issue as N20 and B48. Plastic guide rails wear out, chain elongates. Slightly less loaded on the 3-cylinder.

  Symptoms: Rattling on cold start, engine check light, rough idle
  900–2,800 $
  Ad BMW B38 timing chainBMW B38 chain tensioner
• !! Crankshaft bearing half-shell undersized (early production) from 60,000 km

  Early B38 engines (manual gearbox, built before April 2015) had an undersized crankshaft half-shell bearing. BMW switched to 360° bearings and replaced affected engines as a goodwill gesture (up to 120,000 km / 5 years).

  Symptoms: Knocking or hammering from the engine block under load; oil pressure drop; in extreme cases engine seizure due to spun bearing
  300–5,600 $
  Ad BMW B38 crankshaftnlagerBMW B38 Lagerschale
• !! Compression loss from piston ring wear from 120,000 km

  With neglected maintenance, piston rings and cylinder walls wear. On a three-cylinder, compression loss in one cylinder leads to stalling faster than on a four-cylinder. Replacement engine €4,600–5,600.

  Symptoms: Heavily increased oil consumption, blue smoke, power loss, rough running, misfires.
  1,500–5,600 $

+ 5 more engine weaknesses + vehicle weaknesses