Caution! If the camshafts have been removed from a 6-cylinder engine, take into account the recommended delay after installing them before starting the engine (see chapter 2B).
1. After installing the engine in the car, check the oil and coolant levels. Once again, make sure that everything is connected in the right places (hoses, fuel lines, electrical wiring, etc.). Remove all tools and rags from the engine compartment.
2. Disconnect the ignition and fuel supply system by removing the engine control relay (the relay is located in the engine electrical assembly block)and the fuel pump fuse (located in the main fuse box(see chapter 12). Turn on the starter and rotate the crankshaft until the oil pressure warning light goes out.
3. Replace the relay and fuse. Turn on the ignition and allow the fuel to fill the system.
4. Start the engine. Note that starting may take longer than usual because the fuel system components have been disturbed.
Warning: If you hear a rumbling sound from the camshafts when you first start the engine after a major overhaul, do not be alarmed. Some oil may have leaked from the rocker arm hydraulic mounts. If the rumbling continues, do not accelerate the engine above 2000 rpm until the rumbling stops.
5. While the engine is idling, inspect the engine for fuel, oil, and coolant leaks. Don't be alarmed if the engine smokes or smells bad. This is because the oil and solvents are burning off as the engine warms up.
6. If the engine runs normally, let it idle until hot water flows through the top hose into the radiator. Turn off the engine.
7. After a few minutes, check the oil and coolant levels. Top up if necessary.
8. If pistons, rings and crankshaft liners are replaced during repairs, the engine should be considered new and requires a minimum 800 km run-in. During the run-in, do not allow the engine to run at full throttle or at low revs while driving in any gear. At the end of the run-in, it is recommended to replace the oil and oil filter.
Information obtained from this online resource «BMWMan»