2. Remove the oil pipe from the top of the cylinder head. Make sure you remember the position of all gaskets and washers for assembly.
It is important to replace the glands under the tube mounting bolts.
M10, M20 and M30 engines
1. Adjust all valves to maximum clearance by rotating the eccentric on the valve side of the rocker towards the center of the head (if necessary, refer to the head Car maintenance).
2. Before removing the stop plate, measure the camshaft end play by placing a dial indicator on the front side of the cylinder head and a feeler gauge on the camshaft. Move the camshaft in the cylinder head back and forth. The indicator reading will be the axial play.
3. Compare the readings with the values given in Table of sizes and adjustment data at the end of the Guide.
4. Turn away bolts and remove a persistent plate of a camshaft.
There are two different thrust plate positions. On the M10 and M30 engines, it is fixed in front of the cylinder head behind the flange of the timing gear. On M20 and M40 engines, the thrust plate is located inside the head near the rocker shafts in front of the cylinder head.
5. Remove the cover from the rear surface of the cylinder head - when removing the cover, remember the location of all gaskets, washers and seals.
6. Remove the retaining clips from the rocker arms.
There are several types of clamps. Wire clamps are installed on both sides of the rocker arm; the spring clip is mounted on the rocker itself and covers it on one side.
7. Before removing the rocker shafts, measure the radial clearances of the rocker arms using a dial indicator and compare the results with the values given in Table of sizes and adjustment data at the end of the Guide. Rotate the rocker on the shaft in both directions without sliding it along the shaft. Full span at the end of the rocker arm facing the camshaft will be the radial clearance. If the clearance is too large, the rocker arm bushing or rocker shaft, or both, must be replaced.
8. Remove the retaining rubber or threaded plugs from the front of the cylinder head, depending on the application. There is a plug at the front of each rocker shaft.
If the engine has welded plugs at the front of the rocker shafts, send the cylinder head to a machine shop to remove them to avoid damage to the cylinder head or rocker shafts.
9. Rotate the camshaft until most of the possible rocker arms are free (will not compress the corresponding valve springs).
10. For the rest of the rocker arms, which remained compressing the valve springs, BMW suggests using a special tool in the form of a fork to press the rocker arms onto the springs (thereby removing the spring force from the camshaft cam). If this tool is not available, insert standard screwdrivers into the gaps above the eccentric adjusters on the valve side of the rocker arms. Using screwdrivers, press the rocker arms on the valve springs and hold them while removing the camshaft in this position (see next paragraph). This operation will require at least one assistant, as three or four valve springs usually need to be compressed. If the assistant is not available, then you can try to fix the screwdrivers that compress the valve springs on the board with a strong wire.
Make sure the wire is securely attached to the board and to the screwdrivers, otherwise the screwdrivers may pop out of the cylinder head and cause injury.
11. When all the rocker arms are out of contact with the camshaft cams, slowly and carefully remove the camshaft from the front of the cylinder head.
12. When removing, it may be necessary to rotate the camshaft.
Be very careful not to scratch the camshaft bearing journals when removing.
13. After removing the camshaft, carefully remove the rocker shafts. On models without threaded holes on the front of the shafts, remove the shafts through the rear of the cylinder head using a hammer and a hard wood rod that is slightly smaller in diameter than the rocker shaft.
14. For rocker shafts with threaded holes on the front, use a sliding hammer to remove the shaft.
15. After removing all the rocker shafts from the cylinder head, the rocker arms themselves are removed one by one.
16. Place each rocker in a labeled bag so that they are installed in their original places during assembly. When removing the rocker shafts, remember their position. Guide flat cuts and small oil holes point inward; the large oil ports face down towards the valve guides. Also mark the rocker shafts so that they can be installed in the cylinder head in the same position.
M40 engines
Keep the cylinder head upright until all hydraulic tappets have been removed. If this is not done, then the oil from the hydraulic pushers may leak and they will become inoperative.
1. Check that the camshaft bearing caps are numbered or their position is marked.
2. Therefore, unscrew and remove the bolts securing the camshaft bearing caps,..
... then remove the M40 engine camshaft covers
3. Lift the camshaft off the top of the cylinder head and remove the oil seal from the end facing the timing gear.
4. Prepare a box with compartments filled with engine oil to accommodate the hydraulic tappets so as to store them in accordance with their location. Also prepare another box for pushers.
5. Remove pushers...
...and thrust discs,..
... then remove the hydraulic pushers from the wells in the cylinder head.
All engines
1. Before removing valves, label and store them and their associated components so that they can be stored separately and reinstalled in the same guides.
2. Compress the spring compressor of the first valve and remove crackers. Carefully release the valve spring compressor and remove the retainer, spring and spring seat (if applied).
3. Remove from the valve head, then remove the oil deflector cap from the guide.
4. Repeat the operation for the remaining valves. Don't forget to store all parts of one valve together so they can be reinstalled in their original places.
5. When the valves and related components are removed and stowed in the required order, the cylinder head should be thoroughly cleaned and inspected. If a complete overhaul is being done, complete the engine disassembly before cleaning and inspecting the head.
6. If the valve is stuck in the guide (not retrieved), insert it back into the head and use a small file or abrasive stone to remove the burrs in the groove area under the crackers.