The crankshaft of a six-cylinder engine is rotated by the central bolt of the crankshaft belt pulley. As a tool, you need to use an overhead wrench with an internal dodecagon SW 24 with a ratchet or lever.
Top dead center (TDC) found if mark «ABOUT» on the flywheel will be under the base edge on the gearbox housing (arrow).
Another TDC marking is located in a six-cylinder engine on a belt pulley or on the bottom cover of the toothed belt (arrows).
With cylinder No. 1 at TDC, the large holes in the locking plates on both flywheels of the camshafts face the center of the engine (arrow).
The 1.8 liter engine cover is attached to the right with two clips (1 and 2). Left lining in two places (3 and 4) put on two fastening fingers
The facing of the V-ribbed belt of the six-cylinder engine is put on two fingers at the bottom (1 and 2), at the top it is in two places (3 and 4) screwed.
The arrows show four quick-acting closures, which, when removing the lining of a six-cylinder engine, must be turned to the left by 90°.
In a six-cylinder engine, the toothed belt cover is fastened with two clips (arrows). To dismantle the right toothed belt cover, you must additionally remove the tension roller of the V-ribbed belt (large hex socket bolt).
The arrows show the mounting bolts on the cylinder head cover of the engine with a displacement of 1.6 liters. Bolts become accessible only after dismantling of facing of the engine.
Here, the cylinder head cover of the engine with a displacement of 1.8 liters was dismantled. The arrows mark the position of the mounting bolts.
Too low pressure
Equally low compression pressure readings are nothing to worry about; the reason for low readings may be measurement tolerances that are different for different instruments. But if, when measured on different cylinders, the difference is more than 3 bar, it is worth considering. This could mean the following:
- wear of pistons and piston rings;
- piston rings tightly seated in the grooves as a result of contamination;
- non-circular cylinders as a result of piston jamming;
- deposits on valve stems or valve seats due to combustion products and lubricants;
- burnt valves. In most cases, insufficient compression pressure is caused by leaky valves and therefore reduced engine power. Only the repair of the cylinder head can help.
Troubleshooting
To localize the defect when the compression pressure is too low, a technique is used: a little engine oil is dripped into the spark plug socket with a manual oiler and the compression pressure is measured again.
- If the readings are still below normal, the valves are not in order.
- If the indicators are higher, the point is in the piston rings and, maybe, in the cylinders. The filled oil briefly acted as a gasket between the piston and the cylinder walls, so that the compressed gas found almost no way out.
Pressure loss test (for tightness)
More accurate results are obtained by a tightness test, which can be carried out by some workshops. If the combustion chamber under test loses pressure, this is indicated on the tester scale.
A larger leak can be determined by listening:
- A hiss in the exhaust pipe indicates a leaky exhaust valve.
- Air leaking from the air filter housing indicates a defective intake valve.
- In the event of a defective cylinder head gasket or a crack in the cylinder head, compressed air flows through an adjacent spark plug socket or from an open coolant expansion tank to the outside.
- Worn cylinder walls, piston guides, or piston rings are letting pressure into the crankcase and it is coming out of the open oil filler or dipstick tube.
Engine cranking
1. To do this, place the car with a manual transmission in fourth gear on a flat surface.
2. On a four-cylinder engine, install an SW-24 bent spanner on the center nut of the alternator pulley and now turn the engine over the ribbed V-belt.
3. In a six-cylinder engine, dismantle the lower lining of the engine compartment (chapter Body parts), fit a SW 24 spanner on the central bolt of the crankshaft pulley and turn it using a ratchet or lever.
4. Never rotate the engine using the camshaft timing belt pulley mounting bolt with the timing belt cover removed! The toothed belt may jump over as a result - risk of engine damage.
Setting cylinder No. 1 to the top dead center of the ignition moment
In a four-stroke engine, the piston reaches top dead center twice during four strokes (TDC): once when the intake mixture ignites, the second time after the emission of exhaust gases, with the intake of the fuel-air mixture starting immediately after that. Usually, for various adjustment work, the TDC position of cylinder No. 1 is required.
1. Four-cylinder engine: remove the timing belt cover (described earlier in this chapter). Rotate the crankshaft so that the marking on the timing belt pulley is aligned with the corresponding marking on the cylinder head cover or rear timing belt cover.
2. For greater accuracy, move the crankshaft slightly back and forth so that in the inspection hole on the left in the gearbox bell (hard to reach) marking «ABOUT» on the flywheel stood opposite the edge of the inspection hole.
3. Six-cylinder engine: Remove the right and left toothed belt cover (described in the chapter below).
4. Rotate the crankshaft until the large holes on the fixing plates of both camshaft pulleys are on the inside against each other.
5. If necessary, move the crankshaft back and forth a little or turn it towards you so that the marking in the inspection hole of the gearbox bell «ABOUT» on the flywheel stood opposite the edge of the inspection hole.
Removing the engine cover
1. Four-cylinder engine with a displacement of 1.6 liters: use a large screwdriver to turn the two quick-release fasteners 90°to the left. Remove from hooks and remove lining.
2. Four-cylinder engine with a displacement of 1.8 liters: loosen the two fastening clips on the right side of the trim. Take out facing from the left hook and remove.
3. Raise the trim at the rear edge above the injection valves and pull it out of the plug connection at the front.
4. Six-cylinder engine: use a large screwdriver to turn the four quick-release fasteners 90°to the left.
5. Remove facing.
Removing the V-ribbed belt cover
6 cylinder engine
The V-ribbed belt in the six-cylinder engine runs under the trim on the front of the engine.
1. Remove the engine cover.
2. Loosen the two hexagon socket bolts next to the ignition coil pack.
3. Remove facing upwards from both fixing bolts.
4. When assembling, first put the cladding on the fixing pins.
Removing the cylinder head cover
1. Engine with a displacement of 1.6 liters: remove the retaining clip, remove the crankcase ventilation hose.
2. Dismantle facing of the engine as it is described above.
3. If necessary, remove the cable harness from the clamps.
4. Loosen the fixing nuts.
5. Remove the reinforcing bars (together with high voltage wire brackets).
6. Remove the rear toothed belt cover.
7. Lift the cover.
8. If necessary, remove the oil deflector.
9. Four-cylinder engine with a displacement of 1.8 liters: remove the engine lining as described.
10. Remove ignition coils (chapter Ignition system).
11. Loosen the nine cylinder head cover mounting bolts.
12. Lift the cover.
13. If necessary, remove the oil deflector.
14. Six-cylinder engine: Remove the engine lining.
15. Loosen the mounting bolts.
16. Lift the cover.
17. If necessary, remove the oil deflector.
18. When installing, use a new gasket if possible.
19. 1.6L 4-cylinder engine: Don't forget the shield reinforcing bar under the mounting nuts.
20. 1.8L 4-cylinder engine: Check the two-piece gasket for accuracy.
21. Six-cylinder engine: lightly grease the inside and outside of the cylinder head cover gasket with silicone grease D 007 000 04 (from spare parts).
22. Apply a little Silimate AMV 174 004 01 from Audi Parts to all four lips between the sealing surface of the cylinder head and the camshaft bearing cap. Make sure that the grease hole under the camshaft bearing cap is not clogged.
23. For all models: starting from the middle of the cover, tighten the nuts and bolts crosswise with a tightening torque of 10 Nm.
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