General information
2. During engine operation, parts of the power plant, and in particular the gas distribution mechanism (timing), are heated to high temperatures, resulting in thermal expansion and a slight increase in the size of the parts. To compensate for thermal deformations, it is necessary to have a certain gap between the camshaft cams and the valve lifters.
3. At small gaps, the valves may not close completely, which will lead to a decrease in the efficiency of the engine, and in some cases to deformation of the valves or burning of their seats.
4. With large gaps, the efficiency of the engine also decreases, increased mechanical noise occurs, and the engine becomes uneven.
5. When adjusting the size of the gaps, it is necessary to take into account the condition of the valves - the seal in the valves is satisfactory, the valves do not have excessive gaps in the guides, and the ends of the valve stems are not broken. If these conditions are not observed, it is not possible to correctly adjust the thermal gaps.
6. Checking and adjusting the valves is carried out as necessary, as a rule, during the next scheduled maintenance, as well as after repair / disassembly of the timing or if there is noise during the operation of the valves.
Note: The valve clearances are checked and adjusted according to «cold» engine - engine cooled to ambient temperature.
7. When performing the clearance check procedure, it is recommended to draw up a plate / diagram with the valve numbering in advance for the convenience of recording the measurement results.
8. Before starting work, disconnect the battery and remove the right front wheel
Note: Each time the battery is disconnected, the steering wheel angle sensor must be adjusted.
Z19DT engine
Clearance check
9. Raise the car on a lift and remove the engine crankcase protection.
10. Lower the car and remove the engine cover.
11. Turn out bolts of fastening and disconnect 2 vacuum hoses (see illustration).
9.11 Vacuum hose bolts are indicated by arrows (Z19DT engine)
12. Disconnect the 2 hoses by first loosening and sliding the clamps back completely (see illustration).
9.12 Loosen clamps (1) and remove the hoses (Z19DT engine)
13. Turn away bolts of fastening and remove a cover of the case of a camshaft (see illustration).
9.13 Bolts of fastening of a cover of the case of a camshaft are designated by arrows (Z19DT engine)
14. Turn the crankshaft so that the cams of the first pair (see illustration) were directed upward.
9.14 Pairs of cams for checking gaps (Z19DT engine)
15. Check the gaps of the indicated cams using a set of blade feeler gauges - the appropriate feeler gauge should fit into the gap very tightly with a slight «snacking», otherwise the clearance needs to be adjusted. If the gap value deviates from the standard values, it is necessary to determine the actual gap value - write down the measured value.
16. Turn the crankshaft half a turn in the direction of engine rotation and check the valve clearances at the second (see illustration 9.14) pairs of cams (cams should be pointing up). If the gap value deviates from the reference value, record the result of actual measurements. Then turn the crankshaft another half turn and check the valve clearance at the third and fourth (see ibid) pair of cams.
Gap adjustment
17. Turn the crankshaft so that the drive cam of the valve to be adjusted is turned with the heel towards the pusher.
Note: Make sure the engine is not at the TDC position of the corresponding valve, as changing the shim will require compressing the valve spring, which can cause the valve to stop against the piston crown.
9.18 Turning the cup pusher
18. Rotate the cup pusher with the groove out (see illustration).
19. In the absence of a special device at hand Opel-EN46797 and EN-46799 insert a large flat-bladed screwdriver between the end of the pushrod and the base of the camshaft. Carefully, using a screwdriver as a lever, drown the pusher until it is possible to remove the adjusting washer. Removing the washer is easiest to do with a magnetized rod (see illustration).
9.19 Removing the shim is best done with a magnetized rod
20. Wipe the washer and measure its thickness with a micrometer.
9.20 The thickness of shims is usually stamped on one of their end faces (washers should be installed with markings to the pusher)
Note: Washers are marked (see illustration).
21. The calculation of the thickness of the new shim is made according to the formula:
N = T + A - S
T = thickness of the removed washer, (for example - 3.15 mm)
A = measured valve clearance (for example - 0.45 mm)
S = valve clearance adjustment value (for example - 0.35 mm)
For this example, the thickness of the new shim is N= 3.25 mm.
Note: Adjusting washers can be reused if they do not show obvious signs of wear. It may be possible to make the required adjustment by simply moving the washers from one pusher to another. Record and save for possible future adjustments to the thickness of all washers. If the washer thickness marking is worn out and cannot be read, further use of the washer is not recommended.
22. Prepare a washer of the required thickness, lubricate it with clean engine oil. Squeeze out the pusher and put the washer into it with the marking down.
23. Turn the crankshaft in the direction of engine rotation (clockwise) half a turn and proceeding in a similar manner, adjust the gaps for the second pair of cams, then rotate the crankshaft another half a turn and adjust the gaps of the remaining valves that need adjustment.
24. Turn the crankshaft several times to seat the washers on the tappets, then check the clearances before installing the camshaft housing cover, repeat the adjustment if necessary. Clean the sealing surfaces and install the cover on a new gasket. Torque tighten 7 bolts 10 Nm.
25. Replace all removed elements. Install the crankcase guard and wheel, then lower the vehicle to the ground and tighten the wheel bolts to the correct torque. Connect the battery.
Y30DT engines
26. The procedure for adjusting the valve clearances on the Y30DT engine is the same as described above.
Note: Another special tool is used to remove washers.
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