General information (BMW 3 Series E46)

How to use the information in this chapter

This part of Chapter 2 describes the types of repair work that can be performed without removing the engine from the vehicle. If the engine has already been removed and disassembled as described in Part B, all previous disassembly operations can be ignored.

Keep in mind that while repairs to components such as the piston and connecting rod assembly can be performed without removing the engine from the vehicle, such procedures are not usually performed in isolation from other operations. Other engine components and parts usually require replacement and repair by this point (not counting cleaning of parts and oil channels). Therefore, all such operations are classified as major repairs, and their content is disclosed in Chapter 2B.

Chapter 28 describes the procedures for removing the engine from the vehicle and all repair procedures that can be performed after that.

Engine Description

All 4-cylinder engines have the camshaft located at the top, in the cylinder head. The engine itself is mounted longitudinally, with the gearbox bolted to the rear. The car can be equipped with one of two engine models. The M43TU engine with a displacement of 1.9 liters and a single camshaft was installed from the start of the 3 series until 1998. Since 2001, all cars have been equipped with the N42 engine with a displacement of 1.8 or 2.0 liters, and with two overhead camshafts.

On the M43TU model, a single camshaft is driven from the crankshaft by a chain. The camshaft cams control the valves via rocker arms with hydraulic supports. The camshaft is located in bores made directly in the cylinder head.



The N42 has two camshafts that control 16 valves. The valve timing mechanism has an automatic valve timing adjustment device, known as Valvetronic, which allows adjustment of the phases of both the intake and exhaust valves. The change in phases is achieved by hydraulic devices located between the camshafts and the sprockets, which can change their relative position during engine operation. The design of the valve timing mechanism also allows for changing the lift and duration of the open state of the intake valves using an electromechanical device that changes the position of the fulcrum of the lever located between the cam and the rocker arm of the valve.

The crankshaft has 5 main bearings with liners. The end play of the crankshaft is adjusted by linings installed on the 4th or 5th main bearing (depending on the model). Both engine models are equipped with two balancing shafts rotating in opposite directions.

Engine pistons are selected by weight. The pistons are connected to the upper heads of the connecting rods by floating pins, secured from axial movement in the pistons by spring rings.

The oil pump is located at the front of the cylinder block and is driven by the crankshaft.

Repair operations that can be performed without removing the engine from the car

The following operations can be performed without removing the engine from the vehicle:

• a) Removing and installing the cylinder head.
• b) Removing and installing the timing chain and sprockets.
• c) Removal and installation of camshafts.
• d) Removing and installing the pallet.
• d) Removal and installation of lower connecting rod heads, connecting rods and pistons *
• e) Removing and installing the oil pump
• g) Replacement of power unit supports
• c) Removing and installing the flywheel/faceplate

*These procedures can be performed without removing the engine from the vehicle. However, for better access and cleanliness, they should be performed after the engine is removed.

Information obtained from this online resource: «BMWMAN.ru»