Note 1: Broken valve springs and valve stem seals can be replaced without removing the cylinder head from the engine. This operation will require several special tools and a source of compressed air, so please read the entire paragraph to assess your ability to handle this job.
Note 2. On engines produced since 1998, before starting the operation, check the valve clearances (see chapter 1), since clearance adjustment can be combined with this procedure.
1. Remove the camshaft (see paragraph 7). Remove the tappets from the faulty valve drive. Store the tappets in the order they were installed in the engine. When assembled, they should be pressed back into their previous position.
2. Remove the spark plug from the cylinder with the faulty valve. If you plan to replace all valve caps, remove all spark plugs.
3. Rotate the crankshaft until the corresponding piston is at TDC in the compression stroke (see paragraph 3). If all valve stem seals need to be replaced, start with cylinder #1 and proceed to the next cylinders in turn in accordance with the cylinder firing order (see Technical data at the beginning of this chapter).
4. Screw a long adapter into the spark plug hole, and connect a hose from a compressed air source to the other end (figure 5.4) (compressed air in the cylinder will hold the valves in the up position until the spring is removed from them).
5. Supply compressed air to the cylinder. Be careful: under the action of compressed air, the piston can go down and suddenly turn the crankshaft. If the wrench you used to turn the crankshaft is still on the crankshaft end bolt, it could cause injury or significant damage to the vehicle when turning the crankshaft.
6. The valves should now be held closed using compressed air.
7. Fill all the holes in the cylinder head around the valves with clean rags to prevent any foreign objects from falling into the cylinder. Using a tool, compress the valve spring and remove the crackers from the upper spring plate (figure 5.7).
Note: To compress the springs, you will need a special device that can be secured in the desired location without removing the cylinder head.
8. Remove the upper plate, spring and spring support washer. Note the depth of the cap in the head and pull out the cap (figure 5.8). Label the parts or store them so that the set of parts is in the same place when reassembled.
Note: If the compressed air does not hold the valve closed during this operation, the valve itself or its seat may be damaged. In this case, the cylinder head will have to be removed.
9. Inspect the valve spring for cracks or other damage. Measure the length of the spring in its free state and compare it with the value specified in Technical data of chapter 2B.
10. Lubricate the valve stem with engine oil and insert the new valve stem seal into its seat. Recess the cap to its original depth using a special adapter or a long socket wrench (figure 5.10).
11. Insert the thrust washer and spring (figure 5.12). Install the spring with the coils close together towards the cylinder head.
12. Install the upper valve plate. Compress the spring and carefully insert the crackers into the valve stem groove. To prevent the crackers from falling out during installation, apply a small amount of grease to them (figure 5.12).
13. Slowly release the spring compressor, ensuring that the crackers are securely in place.
14. Turn off the compressed air, disconnect the hose and unscrew the adapter from the spark plug hole,
15. Insert the tappets and install the camshaft (see paragraph 7).
16. Install the remaining parts in the reverse order of removal.
17. Start the engine, check for leaks and unusual noises from the valves.
Note: On pre-1998 models, the hydraulic lifters may make noise initially. This noise should gradually disappear as the lifters fill with oil.