M20 engine (520i, 525i models before April 1990)
1 high voltage distributor
2 Nozzle
3 intake valve
4 viscous coupling
5 toothed belt
6 V-belt
7 Oil pump
8 intake manifold
9 Idle speed regulator
10 Flywheel
M50 engine (models 520i, 525i since May 1990)
1 ignition coils (6 items)
2 Camshafts
3 Hydraulic pusher
4 intake manifold
5 Drive chains
6 Oil filter
7 Thermostat
8 Water pump
9 V-ribbed belt
10 Oil pump (chain driven)
M30 engine (530i, 535i models before August 1992)
1 rocker
2 Drive chain
3 High voltage distributor
4 Viscous coupling
5 Water pump
6 Air mass meter
7 Air accumulator
8 Nozzle
9 Starter
10 Oil dipstick guide tube
11 Oil pump
M21 engine (model 524TD produced before August 1990)
1 Camshaft
2 toothed belt
3 Thermostat
4 Viscous coupling
5 High pressure fuel pump sprocket
6 Vacuum pump
7 Nozzle
8 Glow plug
9 Starter
10 Flywheel
11 Intermediate shaft
12 Generator
M51 engine (Model 525 TD/TDS since September 1990)
1 Camshaft
2 Hydraulic pusher
3 Valve
4 Exhaust turbocharger
5 Thermostat
6 Water pump
7 Oil pump
8 intake manifold
9 Vacuum pump
10 Drive chains
11 Drive belt tensioner
12 V-ribbed belt
13 Viscous coupling