Loosen the cylinder head bolts.
Unscrew the thermostat housing and remove the housing together with the thermostat.
Unscrew the camshaft position sensor and pull it out with the gasket.
Unscrew the top cover of the gear box and remove the cover. Remove the rubber seal from the bottom cover.
Cut from the inside out and remove the gasket between the cylinder head and the top edge of the bottom cover. The gasket must be replaced. Also available as a spare part is a separate gasket for the top cover of the gear box.
Crank the engine at the center bolt of the crankshaft pulley to the right until cylinder 1 is at top dead center. The arrow on the chain sprocket should point up.
Secure the camshafts with the BMW tool shown in the illustration.
Loosen the camshaft sprocket. Squeeze the tension roller at the hexagon and unload the chain. Remove chain sprocket.
Remove the guide rail and tensioner from the cylinder head.
Attention: Before loosening the cylinder head bolts, turn the crankshaft 45 degrees back. This eliminates the possibility of contact between valves and pistons. After installing the cylinder head, return the crankshaft to the top dead center position of cylinder 1.
Loosen cylinder head bolts in several passes from outside to inside. To loosen the bolts, a special Torx wrench is required, e.g. BMW 11 2 250.
Installation
Measure the flatness of the cylinder head and engine block with a steel ruler in the longitudinal and transverse directions and, if necessary, mill (service station work). The maximum allowable non-flatness is 0.03 mm.
Thoroughly clean the holes in the cylinder head from oil and other objects. Notice: Oil must not remain in the blind holes, otherwise the bolts will not fully tighten the cylinder head, although they will be tightened to the correct torque. In addition, the motor block may crack.
Position the cylinder head while pressing the pressure plate outwards.
Tighten the cylinder head bolts in three passes each time in sequence 1 to 10:
- 1st pass: tighten the bolts in sequence from 1 to 10 with a torque wrench to a tightening torque of 30 Nm.
- 2nd pass: Tighten the bolts with a rigid wrench by 90°.
- 3rd pass: Tighten the bolts with a rigid wrench by 90°.
Caution: Be very careful when tightening the cylinder head bolts. Before tightening the bolts, check the accuracy of the torque wrench. In addition, a protractor, such as HAZET 6690, is required to tighten the cylinder head bolts. If a protractor is not available, put the key on the bolt head, attach the square to the key handle and mark the desired angle with chalk. Subsequently, turn the key handle in one pass to the line marked with chalk.
Tighten the bolts for the guide and tensioner bars on the cylinder head.
Turn the crankshaft to the top dead center position of cylinder 1, while the locking pin must be inserted.
Press the hexagon and put on the sprocket with the chain. The arrow on the star should point up. Align the slots in the middle.
Tighten the 4 sprocket bolts to 10 Nm.
Caution: Remove the crankshaft retainer.
Clean the contact surfaces under the gear box top cover.
Check the integrity of the rubber gasket between the upper and lower covers of the gear box and, if necessary, replace. In this case, the convex part of the gasket must fit into the groove in the cylinder head.
Replace the paper gasket of the gear box covers. Cover the gasket joints on the cylinder head with sealing compound "3 Bond 1209".
Coat the upper side of the rubber seal and the BMW tool with a thin layer of grease. Before mounting the cover of the box, the collar is placed on the rubber gasket. In addition, 2 bolts BMW 11 4 110 are screwed in to guide them into the upper threaded hole. Instead of BMW bolts, you can also use a thin sheet of metal and 2 studs.
Push the cover of the gear box, insert the bolts and tighten until their heads fit. Unscrew accessories.
Fit cylinder head cover without gasket. Screw in the MB bolts with large washers -arrows-, while pressing the gear box covers down until the upper edge of the gear box covers is at the level of the cylinder head. In this position, tighten the cover bolts to 10 Nm. Remove the guide bolts and screw in the remaining bolts with a tightening torque of 10 Nm instead.
Unscrew the cylinder head cover and screw it back on, installing the gasket. Tighten the bolts crosswise to 10 Nm.