Removal, Installation and Tensioning of V-Belt

The coolant pump with viscous coupling and the alternator are driven from the crankshaft by a wide V-belt. If air conditioning is fitted, its compressor is driven by an additional V-belt. The belts are arranged one behind the other. To remove the rear belt, the front belt must be removed first.

The V-belt must be replaced if:
a) The belt is brittle or cracked.
b) Noise occurs (for example, due to oil contamination).
c) Damage such as transverse cracks in the cord, cord breaks, dirt or small stones lodged between the cord elements, fraying, or lateral wear of the rubber. Refer to the Drive Belt Condition Check section.

* If the removed belt is to be reused, keep its direction of rotation. Before removing the belt, mark its direction of rotation with chalk.

Air Conditioning Compressor V-Belt Replacement

All models

The A/C compressor is driven by a wide V-belt, which is tensioned automatically.

PROCEDURE
1. Raise and support the vehicle on stands. Remove the bolts and the lower engine compartment cover. Refer to Lower Engine Compartment Cover Removal and Installation.
2. Fit a hexagon key onto the tensioner pulley bolt. Turn it clockwise slowly to compress the hydraulic tensioner element (1). Remove the V-belt. Refer to the accompanying illustration.

3. Fit the new belt according to the belt routing diagram. Turn the tensioner pulley fully to the right, as during removal. Make sure the belt is correctly routed.
4. Release the tensioner pulley by removing the hexagon key. Belt tension is not adjustable.
5. Install the lower engine compartment cover. Lower the vehicle to the wheels.

V-Belt Replacement

Models 520i/523i/528i

The V-belt drives the alternator, coolant pump and power steering pump.

PROCEDURE
1. Remove the fan clutch with fan. Refer to Fan and Fan Clutch Removal and Installation.
2. Remove the cover from the tensioner pulley. Refer to the accompanying illustration.

3. Insert a hexagon key into the bolt on the tensioner pulley. Slowly turn it clockwise to compress the hydraulic tensioner. Remove the V-belt.

4. Fit the new belt according to the belt routing diagram. Turn the tensioner pulley fully to the right, as during removal. Make sure the belt is correctly routed.

5. Release the tensioner pulley by removing the hexagon key. Belt tension is not adjustable by the tensioner pulley.
6. Install the fan clutch with fan. Refer to Fan and Fan Clutch Removal and Installation.

Model 520tds

The diesel engine of the 525tds model has a wide V-belt driving the alternator, coolant pump and power steering pump.

PROCEDURE
1. Remove the fan clutch with fan. Refer to Fan and Fan Clutch Removal and Installation.

2. Use a sufficiently strong screwdriver or a lever on the tensioner element. Press the lever to compress the belt tensioner and remove the belt. Refer to the accompanying illustration.
3. Fit the new belt according to the belt routing diagram. Turn the tensioner pulley fully to the right, as during removal. Make sure the belt is correctly routed.

4. Release the tensioner pulley. Belt tension is not adjustable by the tensioner pulley.
5. Install the fan with viscous coupling. Refer to Fan and Fan Clutch Removal and Installation.