Removal and installation / tensioning the poly V-belt (BMW 5 Series E39)

A wide poly V-belt from the crankshaft drives the coolant pump, the fan with a viscous coupling and the generator. If there is an air conditioning system, the compressor is driven by an additional poly V-belt on all models of cars. Since the poly V-belts are located in parallel planes one behind the other, then to remove the belt located behind, it is necessary to dismantle the belt located in front of it. The poly V-belt is subject to replacement if the following defects are present:

• fragility and presence of cracks;
• noises (for example, if grease gets in);
• transverse cracks in the wedges, destruction of the wedges, deposits of dirt and small stones between the wedges, fringing or wear on the side surfaces of the wedges, see also p. 194.

Note: If the belt being removed is to be reinstalled, mark the direction of its movement with chalk before removing it. This will allow the belt to maintain its previous direction of movement after installation.

Replacing the poly V-belt of the air conditioning compressor (all models)

The air conditioning compressor is driven by a wide poly-V belt with automatic tensioning.

Raise the car. Remove the lower engine compartment cover.



Insert a hex key into the head of the tensioner roller mounting bolt. Slowly turn the key clockwise to compress the hydraulic tensioner "1" and remove the poly V-belt.



In accordance with the diagram shown, place a new poly V-belt on the belt pulleys, while the tension roller, as when removing the belt, is turned to the right until it stops. Pay attention to the incorrect position of the belt in the grooves of the belt pulleys.

Release the tension roller by turning the key counterclockwise. The tension force is set by the tension element. The tension value is not adjustable.

Install the lower casing in the engine compartment. Lower the car.

Replacing the poly V-belt, models 520i/523i/528i

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

Remove the fan with viscous coupling.



Remove the tension roller cover.



Insert a hex key into the head of the tensioner pulley mounting bolt. Slowly turn the key clockwise to compress the hydraulic tensioner and remove the poly V-belt.





In accordance with the diagram shown, place a new poly V-belt on the belt pulleys, while turning the tension roller, as when removing the belt, to the right until it stops. Pay attention to the correct position of the belt in the grooves of the belt pulleys.

Release the tension roller. The tension force is set by the tension element, the tension value is not adjustable.

Install a fan with a viscous coupling.

Replacing the poly V-belt, model 525tds

The poly V-belt in a diesel engine drives the generator, coolant pump and power steering pump.

Remove the fan with viscous coupling.



Place a powerful screwdriver or a suitable lever against the tensioner, see figure. Press the screwdriver down to compress the tensioner and remove the poly V-belt.





In accordance with the diagram shown, place a new poly V-belt on the belt pulleys, while compressing the tensioner as when removing the belt. Pay attention to the correct position of the belt in the grooves of the belt pulleys.

Release the tension roller. The tension force is set by the tension element, the tension value is not adjustable.

Install a fan with a viscous coupling.

Replacing the poly V-belt, model 520d

The poly V-belt in a diesel engine drives the generator, coolant pump and power steering pump.

If necessary, remove the radiator shutters.



Insert the 1/2-inch outer tetrahedron of the end head extension as a lever into the arrow hole.

Caution: Never use a screwdriver for this, as this may damage the hole.

Slowly turn the extension clockwise to compress the hydraulic tensioner. In the compressed position, secure the tensioner with a pin or drill shank, inserting it through hole "1" into the hole in the bracket.

As with the 525tds engine, put a new poly V-belt on the pulleys, while squeezing the tension roller, as when removing the belt. Pay attention to the incorrect position of the belt in the grooves of the belt pulleys.

Release the tension roller and remove the lever. The tension force is set by the tension element, the tension value is not adjustable. If inserted, pull out the locking pin.

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