Engine M20 (models 520i, 525i produced before April 1990.)
1 High voltage distributor
2 Nozzle
3 Inlet valve
4 viscous coupling
5 Toothed belt
6 V-belt
7 Oil pump
8 Intake manifold
9 Idle speed control
10 Flywheel
Engine M50 (models 520i, 525i produced since May 1990.)
1 Ignition coils (6 pieces)
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)
Engine M30 (models 530i, 535i produced before August 1992.)
1 Rocker
2 Drive chain
3 High voltage distributor
4 Viscous coupling
5 Water pump
6 Air flow meter
7 Air accumulator
8 Nozzle
9 Starter
10 Guide tube of oil dipstick
11 Oil pump
Engine M21 (model 524TD produced before August 1990.)
1 Camshaft
2 Toothed belt
3 Thermostat
4 Viscous coupling
5 Toothed pulley of high pressure fuel pump
6 Vacuum pump
7 Nozzle
8 Glow plug
9 Starter
10 Flywheel
11 Intermediate shaft
12 Generator
Engine M51 (models 525 TD/TDS produced since September 1990.)
1 Camshaft
2 Hydraulic pusher
3 Valve
4 Exhaust gas 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
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