1991 BMW 5 Series 520i M50B20 (E34)
E34 / Sedan / Europe / selected global markets
M50B20Registro exacto de año/versiónGold
Engine identity
Oils and fluids
Service and parts data
Common and chronic problems
- Cooling system plastic and hose aging
- Valve cover gasket oil leaks
- Intake boot and vacuum leaks
- Ignition coil/boot misfire
- Idle control valve contamination
First checks
- Confirm VIN/production date
- Confirm M50B20 engine code
- Check oil leaks around valve cover and filter housing
- Smoke-test intake for vacuum leaks
- Pressure-test cooling system
Antes de cambiar piezas
- Save fault codes and freeze-frame data before clearing anything.
- Check engine oil, coolant and transmission fluid using the correct temperature and service procedure.
- Verify power, ground, connectors, hoses, leaks and live data before replacing expensive parts.
Important notes
- 1991 520i is a transition-era E34; market and production month matter.
- Some catalogues separate 520i and 520i 24V; verify by engine code before buying parts.
- Older BMW diagnostic access may require the round 20-pin adapter rather than a normal OBD2 port.