Poly V-belt — inspection and replacement (Audi A4 B6)

The poly V-belt, with longitudinal ribs, is wider than the old V-belts. This belt drives all the important units: the generator, the oil pump for the power steering, the coolant pump and the air conditioning compressor. A belt break would mean the most dangerous accident for the engine, so the belt is made very strong. It is not prescribed to check the belt, but it is a good idea to look at it sometimes, since the belt with a V-shaped cross-section is subject to quite high loads. The belt runs over pulleys, i.e. over wheels with a deep groove located around the circumference. The side walls of the groove touch the sides of the belt. Due to this, the force is transmitted, for this the belt must be taut. The belt tension should not be too strong, otherwise the bearings of the driven units will be destroyed. However, the tension should not be too weak, otherwise the belt will slip with a terrible squeal. Over time, the sides of the poly V-belt wear out, the belt sinks deeper into the groove, and the belt tension decreases. The change in tension is corrected by an automatic tensioner, but it is still worth checking the belt.

Checking the belt surface

1. Turn the engine over several times, this is the only way you can see all the surfaces of the V-belt. Often there is one, but deep crack on the belt, when checking this crack can get right on the pulley.

2. If, when checking the V-belt, uneven traces of wear are found on the side surfaces of the belt, a porous or frayed surface, or even cracks in the belt, the V-belt must be replaced with a new belt or a belt in good condition.

Checking the belt tension

1. Press firmly with your thumb (with a force of approximately 5 kg) on a stretched belt in the middle between two pulleys. The belt should deflect no more than 1.5 cm.



2. Press the belt with more force. The belt should bend with resistance, and the tension roller should move to the side. When you release the belt, the roller returns to its previous position and tightens the belt. If the belt lies loosely on the wheels, this indicates a defective tension roller. The second possible reason: You may have forgotten to remove the locking pin from the tensioner.

Replacing and tensioning the poly V-belt

4-cylinder engines

1. Dismantling: Using a felt-tip pen or wax pencil, draw an arrow on the belt in the direction of belt rotation. When viewed from the belt side, the engine rotates to the right, i.e. clockwise. Marking the direction of rotation is important if the same belt is to be installed later. Installing in the opposite direction increases belt wear and may cause the belt to break.



2. To loosen the poly V-belt, turn the tensioner (shown by arrow).

3. Using a marking mandrel (for example, T10060) lock the tensioner in the place indicated by the arrow.





4. Remove the poly V-belt.

5. The belt is installed in the reverse order. Pay attention to the reliability of the installation of all units (generator, vane pump, air conditioning compressor). Pay attention to the direction of the belt movement, as well as the correct placement of the belt on the pulleys. The belt is first placed on the air conditioning compressor.

6. Start the engine and check the belt operation.

6-cylinder engines

1. Dismantling: Remove the top engine cover. Using a felt-tip pen or wax pencil, draw an arrow on the belt in the direction of belt rotation. When viewed from the belt side, the engine rotates to the right, i.e. clockwise. Marking the direction of rotation is important if the same belt is to be installed later. Installing in the opposite direction increases belt wear and may cause the belt to break.





2. To loosen the belt, use the lever (it is recommended to use lever 3299 with attachment 3299/1) turn the tensioner for the poly V-belt in the direction of the arrow.



3. Remove the belt from the power steering pump pulley.

4. Install the belt in the reverse order. First, place the poly V-belt on the crankshaft pulley. The belt routing ends on the tension roller. Make sure the belt is seated correctly on the pulleys. Start the engine and check the belt movement.



If the vibration damper was removed, then during installation you should pay attention to the following:

4-cylinder engines

The lock mounting bracket is in the service position, the poly V-belt is removed. The vibration damper (pulley) must be installed using original screws only. Installation is possible in only one position. The hole (arrow) of the vibration damper must be above the protrusion on the toothed belt wheel.

6-cylinder engine

The lock mounting bracket is in the service position, the poly V-belt is removed. (To remove the vibration damper, it is not necessary to loosen the central screw). Installation using original screws only. The notches (arrows) in the vibration damper must match the locking protrusions on the toothed belt wheel.



[Text provided by the online resource: AudiManual.ru]