The toothed belt on a 6-cylinder engine is correctly tensioned if it can be rotated no more than 90°between the toothed belt drive gear and the upper guide roller with your fingers.
In the engine with a displacement of 1.8 liters, the top cover of the toothed belt is also fastened with clips (2 and 3). When mounting, the protrusions (1) on the bottom of the lid must be correctly inserted into the bottom of the lid.
A lot of effort is required to remove the bottom cover of the toothed belt in an engine with a displacement of 1.8 liters. in numbers (1–4) the location of the mounting bolts is indicated.
Shown here are both pistons (1 and 2) toothed belt tensioner in four-cylinder engines.
Toothed belt tensioner for 4-cylinder engine. The numbers indicate:
- 1 - wrench with two holes for setting the toothed belt tension (text at the top);
- 2 - fixing bolt.
The tensioner pulley with a six-cylinder engine is located in a rather hidden place on the right front on the engine block. The arrow indicates the clamping bolt.
On a dismantled engine with a displacement of 1.8 liters, the location of some nodes is visible
- 1 - crankshaft belt pulley;
- 2 - a tension roller of a toothed belt;
- 3 - camshaft timing belt pulley;
- 4 - Hall sensor;
- 5 - toothed belt;
- 6 - device for tensioning the V-ribbed belt;
- 7 - radiator fan bearing;
- 8 - water pump V-belt pulley.
Engine with a displacement of 1.8 liters. TDC mark (2) on the camshaft timing belt pulley and the mark corresponding to it (1) on the cylinder head cover must be opposite each other in the same way as the TDC mark (4) on the crankshaft pulley and the corresponding arrow (3) on the bottom cover of the toothed belt.
With an engine with a displacement of 1.6 liters, the mark on the pulley (2) camshaft toothed belt must correspond to the mark in the form of an arrow (1) on the back cover of the toothed belt. TDC of the crankshaft in the same position as in the engine with a displacement of 1.8 liters.
As a silent drive element located (s) on top of the camshaft (ov), serves as a toothed belt driven by a crankshaft.
The timing rubber belt with steel wire insert runs without wear, while the timing belt rubber compound provides dry lubrication of the belt pulleys. In a 6-cylinder engine, the toothed belt drives the water pump in addition to the camshaft. In a 4-cylinder engine, the belt additionally drives the intermediate shaft, which in turn drives the oil pump and ignition distributor (only in 1.6 l engine).
Tip: To carry out work on the toothed belt, the vehicle with the four-cylinder engine must be brought into the so-called service position (head body parts). In this case, the front part is removed from the car and retracted to a certain distance with the help of bolts. In order to improve access, we recommend that you also remove the toothed belt in the 6-cylinder engine.
Removing the toothed belt cover
1. Four-cylinder engine: Remove the air intake hose by unscrewing the two Phillips head screws on the front of the vehicle.
2. Wring out two fixing collars at the top of the cover.
3. Lift up the top of the cover.
4. When installing, make sure that the bottom edge of the cover is correctly inserted into the opposite part, otherwise it will not be securely fixed.
5. In most cases, it is enough to dismantle the top part of the cover. It is also more difficult to dismantle the lower part of the cover.
6. Bring the front of the car to the service position (chapter Body parts).
7. Remove the viscous fan (chapter Cooling system).
8. Remove the V-ribbed belt and unscrew the belt tensioner.
9. Unscrew the V-ribbed belt pulley at the crankshaft and the water pump V-ribbed belt pulley.
10. Loosen the fixing bolts or nuts of the lower toothed belt cover and remove it.
11. During installation, the bolts are tightened as follows: V-ribbed belt pulley at the crankshaft with a tightening torque of 25 Nm (follow the fix), V-ribbed belt pulleys at the water pump 20 Nm, nuts or bolts of the toothed belt cover 10 Nm.
12. 6-cylinder engine: remove the viscous fan.
13. Remove the ribbed V-belt with the ribbed V-belt tensioner.
14. Loosen the top and bottom of each half of the toothed belt cover, one tie-down collar.
15. Carefully remove the cover from the rest of the hooks.
Checking the condition of the toothed belt
1. Remove the toothed belt cover.
2. The toothed belt must not be oily or cracked.
3. The sides of the teeth must be in good condition and show no signs of wear.
4. So that you can inspect the belt along its entire length, turn the crankshaft as described in the chapter below.
5. Be sure to replace the damaged toothed belt.
Checking the toothed belt tension
The four-cylinder engine has a spring-loaded toothed belt tensioner that automatically sets the correct belt tension. In this regard, only the belt tension mechanism is checked. The six-cylinder engine has a static belt tension.
1. Four-cylinder engine: remove the top timing belt cover.
2. Press the belt between the pulleys and watch the spring tension roller: the tension roller should be pressed out and return to its original position when the belt is released. In this case, the belt tensioner is in order.
3. Use a mirror to check in which range of the scale the edge of the piston is located.
4. Range «A»: Everything is fine.
5. Range «IN»: normal wear area; adjustment can be saved.
6. Range «WITH»: mechanism needs to be adjusted (see next section) or there is a defect in the toothed belt or tensioner pulley.
7. Six-cylinder engine: remove the toothed belt cover.
8. Take a measurement between the camshaft pulley and the top take-off roller on the right side of the cylinders when viewed in the direction of travel.
9. A cold toothed belt should rotate 90°when properly tensioned (= right angle) only thumb and forefinger.
Setting the toothed belt tension
4 cylinder engine
Installation is carried out with a cold and warm engine using a two-hole wrench, such as Hazet 2587.
1. Remove the top cover of the toothed belt, loosen the fixing bolt.
2. Turn the toothed belt tensioner with a wrench so that the piston «1» fully extended and the piston «2» raised the tensioner about 1 mm.
3. Tighten the fixing bolt of the tension roller first by hand.
4. Rotate the crankshaft two turns in the direction of travel (right).
5. Check if the range is located «A» on the scale opposite the top edge of the piston «2».
6. If this cannot be done due to poor access, then it can be measured «D» = 25–29 mm.
7. If installation still does not correspond to norm, then tighten still and for check again turn a cranked shaft.
8. When properly installed, tighten the tensioning roller mounting bolt with a tightening torque of 25 Nm.
9. Rotate the crankshaft one revolution and recheck the toothed belt tension.
Setting the toothed belt tension
6 cylinder engine
1. First remove the toothed belt cover.
2. Remove the V-ribbed belt and its tensioner.
3. Loosen clamping bolt (with hexagon socket 8 mm) on the tension roller.
4. Turn the tension roller to the right with an 8 mm Allen key and turn it down until the belt tension is correct.
5. Hold the idler in this position.
6. Using an 8 mm Allen key, tighten the tension roller clamping bolt (45 Nm).
7. Rotate the crankshaft one revolution and recheck the toothed belt tension.
Replacing the toothed belt, setting the valve timing
The description of the process of replacing the toothed belt refers not only directly to this work, but also to the dismantling and installation of the cylinder head, while the toothed belt must inevitably be removed.
The installation of a toothed belt, logically, also involves the installation of valve timing. But in order to avoid confusion, it must be remembered that the valve timing does not change as a result of wear. Installation is carried out only once, if the toothed belt was previously removed.
Tip: Only with the correct installation of the gas distribution phases is the coordinated operation of the valves and the gas distribution mechanism ensured. Incorrectly set valve timing causes low engine power and in extreme cases can even lead to severe engine damage when the piston base hits untimely closed valves. Installation in different types of engines is done in different ways.
Audi no longer provides for the replacement of the toothed belt as part of the vehicle's regular maintenance. However, we would still change the belt after 150,000 km. If the toothed belt breaks, a new motor will be needed. Compared to this, a preventive replacement of a toothed belt costs a penny.
Is it possible to do this on your own?
Timing belt replacement poses different problems depending on the engine model:
- With a four-cylinder engine, changing the toothed belt is a laborious job in general, but professionally it is not too much of a problem. It does not require special tools.
- With a six-cylinder engine for setting the valve timing (what becomes necessary after dismantling the toothed belt and cylinder head) you need to absolutely accurately fix the camshafts and crankshaft in the TDC position using special tools (tools 3242 and 3243). You must purchase the mentioned tools.
Toothed belt replacement
4 cylinder engine
1. Bring the front of the car often to the service position (chapter Body parts).
2. Remove the viscous fan.
3. Remove the V-ribbed and V-ribbed belts, unscrew the belt tensioner (chapter Generator).
4. Remove the V-ribbed belt pulley at the crankshaft after loosening the hexagon socket bolt (not center bolt).
5. Unscrew the water pump V-belt pulley.
6. Remove the top part of the toothed belt cover.
7. Loosen the fixing bolts and nuts of the toothed belt bottom cover and remove it.
8. Put the piston in cylinder 1 in the ignition position at TDC, see earlier in this chapter.
9. Mark the direction of travel on the toothed belt for later assembly. Keep the same direction of movement of the used belt.
10. Loosen the tension roller mounting bolts and remove the toothed belt.
11. Apply a new toothed belt. If the position of the crankshaft pulley and camshaft has not changed, then the valve timing is still set correctly. For the sake of safety, they still need to be checked before the final assembly:
12. Turn the camshaft timing belt pulley so that the pulley marking is under the arrow on the back cover of the timing belt (engine with a displacement of 1.6 liters) or under the mark on the cylinder head cover (engine with a displacement of 1.8 liters).
13. If you now need to turn the camshaft, then this can only be done when the piston is in the TDC position, otherwise the valves or piston bases can be damaged.
14. The TDC mark of the crankshaft is checked through the inspection hole on the gearbox.
15. At the engine with a working volume of 1,6 l check up also position of an intermediate shaft. To do this, remove the cover of the ignition distributor and check if the distributor finger points to the mark in the edge of its housing. If not, turn the intermediate shaft so that the marks match.
16. Fit the toothed belt, making sure that the position of the various pulleys does not change.
17. Tension the toothed belt as described above.
18. For all models: turn the crankshaft fully two times and check the installation again.
19. Screw the bottom cover of the toothed belt with a tightening torque of 10 Nm.
20. Fasten the camshaft poly V-belt pulley with a tightening torque of 25 Nm. At the same time, make sure that the cover is in the correct position: depending on the engine model, either the fixing pin must enter the belt pulley, or the mounting holes of the belt pulley are located asymmetrically. In this case, all mounting holes must match the holes on the crankshaft.
21. The rest of the assembly is carried out, respectively, in the reverse order of dismantling.
22. 1.6 L engine: adjust the ignition.
Toothed belt replacement
Six-cylinder engine
1. Remove the V-ribbed belt together with the tensioner (chapter Generator).
2. Remove the toothed belt covers on both sides.
3. Turn the crankshaft to the ignition position at the TDC of cylinder 1. The marks on the crankshaft pulley and timing belt cover must match, the large holes on the fixing plates on the camshaft pulleys must face each other towards the center of the engine.
4. Unscrew the ignition timing sensor from the crankcase and screw in the special tool instead «Crankshaft mount 3242». Tighten lightly.
5. Remove the crankshaft V-ribbed belt pulley, unscrew the bottom cover of the toothed belt.
6. Mark the direction of movement of the toothed belt for subsequent installation. Keep the same direction of movement of the used belt.
7. Loosen the toothed belt tensioner, remove the toothed belt.
8. Installation: special tool «Camshaft Mount 3243» install on the camshaft fixing plates.
9. Loosen the camshaft pulley bolts only about three turns.
10. Remove special tool 3243 again.
11. Remove both camshaft pulleys from the cone. Use tongs for this purpose. Install clamps on the reverse side of the toothed belt pulley hub; bolt stays the same (loosened by three turns).
12. After completing the preliminary work, the installation now begins:
13. For further work, a new timing belt must now be applied. When applying a used belt, take into account the direction of its movement.
14. Reinstall the special tool on the camshaft fixing plates «Camshaft Mount 3243».
15. Check again that the special tool is installed correctly.
16. The camshaft pulleys must be put on a cone so that they rotate on the shaft, but do not swing (screw is screwed by hand).
17. Now tighten the timing belt (see chapter above).
18. Tighten the camshaft pulleys with a tightening torque of 30 Nm and then finally tighten the bolts another 1/2 turn (180°).
19. Remove the special tool.
20. Reassemble the dismantled parts.
The figure shows the installation of special tool 3243 for fixing the camshafts in the TDC position for a six-cylinder engine.
Shown here is tool 3242 and where it is screwed into the cylinder block to secure the crankshaft.
In order to install special tool 3243, you need to unscrew from the crankcase (1) ignition timing sensor (2) six-cylinder engine.
Removing the camshaft timing belt pulley using a puller with the fixing bolt loosened.
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