Opel Corsa B 1993–2000 Service and Repair Manual: Cylinder head - overhaul

1. With the cylinder head removed, clean away external dirt.

2. Remove the valves, springs and associated components. Note that both inlet and exhaust valve springs have seats, but they are different (see illustration).

Exhaust valve spring rotator seat (A) and inlet valve spring seat (B)

3. Inspect the valves, valve seats, guides and springs. Regrind or renew as necessary.

4. Check the head sealing surface for warping by placing in on a piece of plate glass, or using a straight-edge and feeler blades. Slight distortion, or corrosion, may be corrected by machining. Seek expert advice if this is necessary: the removal of too much metal will render the head useless.

5. Check the valve lifter bores in the cylinder head for wear which, if evident, will mean renewal of the cylinder head. Also check the valve lifter oil supply holes in the cylinder head for any sign of contamination.

6. On engines which have covered a high mileage, or for which the service history (particularly oil changes) is suspect, it is possible for the valve lifters to suffer internal contamination, which in extreme cases may result in increased engine top-end noise and wear. To minimise the possibility of problems occurring later in the life of the engine, it is advisable to dismantle and clean the hydraulic valve lifters as follows whenever the cylinder head is overhauled. Note that no spare parts are available for the valve lifters, and if any of the components are unserviceable, the complete assembly must be renewed (see illustration).

Hydraulic valve lifter components

1. Collar
2. Plunger
3. Ball
4. Small spring
5. Plunger cap
6. Large spring
7. Cylinder

7. Carefully pull the collar from the top of the valve lifter cylinder. It should be possible to remove the collar by hand-if a tool is used, take care not to distort the collar.

8. Withdraw the plunger from the cylinder, and recover the string.

9. Using a small screwdriver, carefully prise the cap from the base of the plunger. Recover the spring and ball from under the cap, taking care not to lose them as the cap is removed.

10. Carefully clean all the components using paraffin or a suitable solvent, paying particular attention to the machined surfaces of the cylinder (internal surfaces), and piston (external surfaces). Thoroughly dry all the components using a lint-free cloth. Carefully examine the springs for damage or distortionthe complete valve lifter must be renewed if the springs are not in perfect condition.

11. Lubricate the components sparingly with clean engine oil of the correct grade, then reassemble as follows.

12. Invert the plunger, and locate the ball on its seat in the base of the plunger (see illustration).

Locate the ball (1) on its seat (2) in the base of the plunger

13. Locate the smaller spring on its seat in the plunger cap, then carefully refit the cap and spring, ensuring that the spring locates on the ball. Carefully press around the flange of the cap, using a small screwdriver if necessary, until the flange is securely located in the groove in the base of the plunger (see illustrations).

Spring (1) located in plunger cap, and ball (2) located on seat in plunger

Locate the cap flange in the plunger groove

14. Locate the larger spring over the plunger cap, ensuring that the spring is correctly seated, and slide the plunger and spring assembly into the cylinder (see illustrations).

Locate the spring over the plunger cap . . .

. . . then slide the plunger and spring assembly into the cylinder

15. Slide the collar over the top of the plunger, and carefully compress the plunger by hand, until the collar can be pushed down to engage securely with the groove in the cylinder (see illustration).

Slide the collar (1) over the top of the plunger and engage with the groove (2)

16. On some engines an oil pressure regulating valve in the head stabilises the oil pressure applied to the valve lifters (see illustration). To renew the valve, access is gained via the circular plug covering the end of the valve. The old valve must be crushed and its remains extracted, and a thread (M10) cut in the valve seat to allow removal using a suitable bolt. A new valve and plug can then be driven into position. Care must be taken to keep foreign matter and swarf out of the oilways; it is probably best to have the valve renewed by a GM dealer if necessary.

Cylinder head oil pressure regulating valve (arrowed)

17. Refit the valves, springs etc. Remember to fit new valve stem seals.

18. On 1.6 (16SH), 1.8 and 2.0 litre engines, take the opportunity to renew the thermostat housing sealing ring whilst the head is removed.