The 2019 Z4 M40i shares the excellent B58 engine with the Supra but uses the ZF 8HP transmission that can develop cooler and mount issues. The catastrophic engine failures listed (pistons, bearings, rebuilds) are rare but often trace to oil starvation during aggressive track use or severely neglected maintenance.
ZF 8HP Transmission Oil Cooler Failure
Occasional · high severityTypical onset: 50,000-90,000 mi
Symptoms: transmission overheating warnings, limp mode during spirited driving, burnt ATF smell, slipping or delayed shifts when hot
Fix: Replace transmission oil cooler and flush ATF; requires dropping the transmission pan and sometimes subframe work depending on accessibility. 4-6 hours labor.
Estimated cost: $1,200-2,000
Transmission Mount Deterioration
Common · medium severityTypical onset: 40,000-70,000 mi
Symptoms: clunking on shifts especially reverse to drive, excessive driveline vibration at idle, rough engagement from stops
Fix: Replace transmission mount and often engine mounts while you're in there; each mount is 1-2 hours, but doing all three at once is 4-5 hours total.
Estimated cost: $800-1,500
B58 Catastrophic Bearing/Piston Failure
Rare · high severitySymptoms: sudden metallic knocking from engine bay, loss of oil pressure, engine seizure, metal shavings in oil
Fix: Almost always requires complete engine rebuild or short block replacement. Root cause is typically oil starvation from extended high-RPM track sessions without baffled pan, or running severely overdue on oil changes. 30-50 hours labor for rebuild, 20-25 for short block swap.
Estimated cost: $8,000-15,000
High-Pressure Fuel Pump (HPFP) Failure
Occasional · high severityTypical onset: 60,000-100,000 mi
Symptoms: long crank before starting especially when hot, misfires under heavy load, limp mode with fuel system codes P0087/P0088, rough idle and hesitation
Fix: Replace HPFP and fuel filter; BMW revised the pump design in later production. Located on engine side, accessed from top. 3-4 hours labor.
Estimated cost: $1,800-2,800
Coolant System Leaks (Expansion Tank and Hoses)
Occasional · medium severityTypical onset: 50,000-80,000 mi
Symptoms: coolant smell in cabin or engine bay, low coolant warnings, visible drips under car after parking, slow overheating in traffic
Fix: Plastic expansion tank cracks at mounting tabs; upper radiator hose connections also fail. Replace tank, pressure test system, replace any aging hoses. 2-3 hours labor.
Estimated cost: $600-1,100
Convertible Top Hydraulic System Issues
Occasional · low severityTypical onset: 30,000-60,000 mi
Symptoms: top moves slowly or stops mid-cycle, hydraulic pump runs excessively, creaking during operation, top won't latch properly
Fix: Usually hydraulic fluid leak from rams or pump; sometimes just needs bleeding and topping off. Full ram replacement is 6-8 hours, pump is 3-4 hours. Diagnosis critical here.
Estimated cost: $1,200-3,500
Buy one if you can verify religious oil change history and it hasn't been tracked hard without proper oiling mods—the B58 is bulletproof when maintained, but the transmission and top will need attention as it ages.
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.