Note: Broken valve springs and defective piston rod seals can be replaced without removing the cylinder head. This operation usually requires two special tools and a source of compressed air.
1. According to the recommendations section 3 remove the timing cover from the desired cylinder head. If you are replacing all valve stem seals, remove both timing covers.
2. Remove the spark plug from the defective cylinder. If all valve stem seals are being replaced, all spark plugs must be removed.
3. Turn the crankshaft until the piston in the cylinder is at TDC in the compression stroke (see instructions in section 11). If you are replacing the seals on all the valve stems, start with cylinder #1 and work on the valves of each cylinder one at a time. Go from cylinder to cylinder in the firing order (1 - 4 - 2 - 5 - 3 - 6).
4. Screw the adapter into the spark plug hole and connect an air hose from a compressed air source to it.
5. Remove the bolt, hinge pin and lever from the defective valve and pull out the rod. If the seals of all valve stems are being replaced, then all levers and rods must also be removed (see section 4).
6 Apply compressed air to the cylinder. The valves should be held in place by the air pressure. If the valve surfaces or seats are in poor condition, leaks may prevent the valves from being held by the pressure, in which case use the recommendations below.
7. If you do not have access to compressed air, use an alternative method. Set the piston to just before TDC on the compression stroke, then thread a long piece of nylon rope through the spark plug hole until it fills the entire combustion chamber. Make sure the other end of the rope hangs out so that it can be pulled out easily. Use a long socket wrench to rotate the crankshaft in its normal direction of rotation until you feel a slight resistance.
8. Place a clean rag in the holes in the cylinder heads above and below the valves to prevent parts and tools from falling into the engine, then use a valve spring compressor to compress the spring. Remove the crackers with small needle-nose pliers or a magnet (see illustration).
Note: There are a couple of different types of tools available to compress the valve springs without removing the head. One of them grips the lower spring rings and presses on the retainer when turning the handle; the other, shown in this manual, uses the valve lever bolt as the lever arm. Both types have proven themselves to be good.
9. Remove the spring retainer screen and valve spring assembly, then remove the valve stem umbrella seal in the guides (see illustration).
Note: If the valve is not held closed by air pressure, its working surface or seat is damaged. In this case, the cylinder head should be removed for additional repair.
10. Tie a rubber band or tape around the top of the valve stem to prevent the valve from falling into the combustion chamber, then turn off the air.
Note: If using a string instead of air pressure, turn the crankshaft slightly in the opposite direction to its normal rotation.
11. Check if the valve stem is damaged. Rotate the valve in the guides; if its end moves along an eccentric trajectory (deviates from the axis of rotation), it means it is bent.
12. Move the valve up and down the guides and make sure it does not stick. If the valve stem sticks, then either the valve is bent or the guides are damaged. In either case, the head must be removed and repaired.
13. Apply compressed air to the cylinder to keep the valve closed, then remove the rubber band or tape from the stem. If a rope was used instead of compressed air, turn the crankshaft in the direction of its normal rotation until a slight resistance is felt.
14. Lubricate the valve stem with engine oil and install a new umbrella guide seal (see illustration). On 3.0L engines, the seals on the intake have a silver rim, on the exhaust - a red rim.
15. Install the spring assembly and spring seat (where necessary) in position above the valve (see illustration).
16. Install the valve spring retainer. Compress the valve spring assembly.
17. Install the crackers into the grooves. You can apply a small amount of grease to the holders to secure them in place. Release the pressure and make sure the holders are in place.
18. Disconnect the air supply hose and remove the adapter from the spark plug hole. If a rope was used instead of air, remove it from the cylinder.
19. Install the valve levers and pushrods as recommended in section 4.
20. Install the spark plugs and connect the wires to them.
21. Install the timing cover as recommended section 3.
22. Start and warm up the engine, then check for oil leaks and listen for any unusual sounds coming from the timing cover area.