Withdrawal
1. Relieve fuel pressure on all fuel injected engines (see chapter Supply system).
2. Disconnect the negative battery cable. Where the battery is located in the engine compartment, it can be completely removed from the vehicle (see chapter Ignition system).
If your car's radio is equipped with an anti-theft system, make sure you have entered the correct code before disconnecting the battery.
If, after connecting the battery, the inscriptions on the instrument panel appear in the wrong language, refer to Section Anti-theft audio system and instrument panel language, for instructions on how to set the desired language.
3. Remove the air cleaner assembly (see chapter Supply system).
4. Disconnect the wiring from the ignition distributor (if necessary, first mark the location of all wires) and BB wire from the ignition coil (see chapter Ignition system).
5. Disconnect the wire from the coolant temperature sensor block (see chapter Cooling system).
6. Disconnect the fuel lines from the fuel line or carburetor as provided (see chapter Supply system).
7. Drain the cooling system (see chapter Cooling system).
8. Clearly label and then disconnect all other hoses from the throttle body, intake manifold, carburetor and cylinder head as provided.
9. Disconnect the exhaust manifold from the cylinder head (see Section Removal and installation of a final collector). Depending on the type of engine, you may not have to disconnect the manifold from the exhaust pipe; however, on right-hand drive models, the intermediate steering column shaft may block access to the cylinder head clearance screws.
10. Disconnect all remaining hoses and tubes from the intake manifold, including the ignition timing vacuum tubes, as well as the heater and cooling system hoses.
11. On early carbureted models, disconnect the wiring from the alternator and starter.
12. Remove the inlet pipeline (see Section Removal and installation of the inlet pipeline). Do not disassemble or remove any fuel injection system components unless absolutely necessary.
13. Remove the fan drive belt and the fan itself (see chapter Cooling system).
14. Remove the cylinder head cover and its gasket (see Section Removal and installation of a cover of a head of cylinders). Remove the semi-circular rubber seal from the front of the cylinder head where it is not integrated into the cover gasket.
15. Bring the piston No. 1 to the TDC position of the compression stroke (see Section Bringing the piston of the first cylinder to the top dead center position (TDC)).
16. Remove timing belt or chain (see Section Removal, inspection and installation of the distribution chain and sprockets of its tensioner or Replacing the front seals).
If you want to save time removing and installing the timing belt or chain and re-arranging the engine, you can detach the camshaft sprocket and hang it off to the side with a piece of rope without removing the chain or belt. The rope should leave the chain or strap taut so that it cannot slip off the sprockets.
17. Loosen the cylinder head bolts gradually, a quarter of a turn each time, in the reverse order of tightening (see photo 6, 7, 8, or 9). On engines M10, M20 and M30 this time do not disassemble or remove rocker assembly.
18. Remove the cylinder head by lifting it straight up from the cylinder block. Do not push anything between the cylinder head and cylinder block, as the sealing surfaces of the gasket may be damaged. Instead, place a blunt rod into the inlet to gently release the head.
19. Remove any remaining external components from the head so that it can be thoroughly cleaned and inspected. The cylinder head maintenance procedure is described in Part Engine Component Overhaul Procedures. On M40 engines, remove the rubber o-ring from the groove in the top of the oil pump housing/front cover.
Installation
1. When installing the cylinder head, the mating surfaces of the head and cylinder block must be absolutely clean.
2. Use a scraper to remove all traces of charcoal and old gasket material, then clean the mating surfaces with a suitable solvent. If there is oil on the mating surfaces when the head is installed, the gasket will not seal properly and leaks may occur. When working on the cylinder block, pack the cylinders with a clean rag to prevent dirt from entering them. Use a vacuum cleaner to remove material residues trapped in the cylinders.
3. Check the mating surfaces of the head and block for nicks, deep scratches and other damage. If the damage is minor, they can be eliminated with a file; if they are serious enough, then only mechanical processing can correct them.
4. With a suitable size tap, go through the threads in the head bolt holes, then clean the holes with compressed air - make sure that nothing is left in the holes (including oil, water, etc.).
5. BMW experts recommend replacing the head bolts, but if you still use old bolts, clamp each of them in a vise and go through it with a lerk. To remove traces of corrosion and restore the thread. Dirt, corrosion, traces of sealant, and damaged threads affect bolt torque readings.
6. If bolts or their threads are damaged, use new bolts.
7. Install all components removed from the head before cleaning and inspecting it. On M40 engines, install a new O-ring into the groove in the top of the oil pump housing/front cover.
8. Make sure that the sealing surfaces of the gasket between the cylinder block and the head are clean and free of grease. Install the head gasket on the block with the side specified by the manufacturer facing up (usually written on it «UP», «OPEN» or something similar). Use the dowel pins on the top of the block to properly position the gasket.
9. Carefully install the cylinder head on the block. Use guide pins for proper alignment.
10. On models where the engine is slightly tilted (e.g. M40 engine), Installing guide rods to more accurately align the position of the head on the block can help. To do this, use two old head bolts screwed into both ends of the block. Cut off the bolt heads and use a hacksaw to make slots in their tops so that after installing the cylinder head they can be removed.
11. Fit the cylinder head bolts.
12. Tighten the head bolts in the sequence below to the correct torque.
TIGHTENING sequence for cylinder head bolts for M10 four-cylinder engines.
TIGHTENING sequence for cylinder head bolts for M20 six-cylinder engines.
TIGHTENING sequence for cylinder head bolts for M30 six-cylinder engines.
TIGHTENING sequence for cylinder head bolts for four-cylinder M40 engines.
13. Please note that on some engines the final tightening step occurs after the engine has been run.
14. Perform the rest of the installation in the reverse order of removal. On engines M10, M20 and M30, before installing the cylinder head cover, adjust the valve clearances (see chapter Car maintenance) - Check them again after warming up the engine. Start the engine and check for leaks.