Balance shafts — general information, removal and installation (BMW 3 Series E46)

General information

1. To compensate for unbalanced engine sips and eliminate vibrations during its operation, 4-cylinder N42 engines are equipped with two balance shafts with counterweights at the ends. The shafts rotate in opposite directions and are driven by a chain from the crankshaft sprocket. The shafts are part of a common unit with the oil pump, so the removal and installation of the balance shafts is described in detail in paragraph 17 as part of the procedure for removing and installing the oil pump.

2. The M43Ti engines are also equipped with balance shafts, but they are also gear driven from the crankshaft. Unlike the N42 engine, the balance shafts can be removed and installed independently of the oil pump. Therefore, the following description applies only to the M43TU engine.

Removal (m43TU engines only)

3. Remove the oil pan as described in paragraph 1 3.

4. Turn the engine crankshaft so that pistons #1 and #4 are at TDC. Fix this position by inserting a rod into the engine flywheel (see paragraph 3).

5. In the reverse order to that shown in Fig. 16.8, unscrew the balance shaft housing mounting bolts. Remove the housing together with the shafts. Keep in mind that the housing is heavy. Remove the gasket between the shaft housing and the cylinder block.

Installation (m43TU engine)

6. Make sure that the camshaft housing dowel pins are in place in the cylinder block. Place spacers on them. Note: If the cylinder block, crankshaft or balance shaft housing has been replaced, the camshaft drive gear clearance will need to be checked and adjusted during installation. To prevent damage, install the thickest camshaft spacer (2.25 mm) first during the initial stage of this procedure.



7. Turn the balance shafts so that the holes in the front ends of the shafts are facing downwards (at the 6 o'clock position relative to the cylinder block) (Fig. 16.7).



8. Install the shaft housing on the pins and screw in the bolts. If the clearance in the engagement requires adjustment (see previous point), screw in the old bolts, as the housing may have to be removed and installed again to replace the spacers. If the engagement does not require adjustment, screw in the new bolts directly. Tighten the bolts to the specified torque in the sequence shown in Fig. 16.8.



9. To measure the clearance in the engagement of the drive shaft gears, install a dial indicator and press its feeler gauge to the side surface of the tooth of the driven gear. Turn the gear one way to select the clearance in the engagement and reset the indicator. Turn the driven gear the other way to again select the clearance and read the instrument reading. Remove the locking rod from the flywheel, turn the crankshaft 120° and measure the clearance again. Then do the same thing, turning the crankshaft 240°. Find the average clearance value by adding all three readings and dividing the sum by three. Compare the obtained value with the Technical Data. If the clearance requires adjustment, replace the spacer shim under the shaft housing. Reducing the shim thickness by 0.03 mm reduces the clearance in the engagement by 0.02 mm. Keep in mind that the shims under both sides of the shaft housing must be of the same thickness. After completing the adjustment, tighten the shaft housing mounting bolts to the required torque.



10 Install the oil pan as described in paragraph 13.

(Information obtained from this online resource «BMWMAN.ru»)