Valve: Service and Repair
WM 156120 Removing and installing valves
Tools
Preliminary work
1. Remove cylinder head. -> 157019 Removing and installing cylinder head Service and Repair
2. Remove camshafts. -> 150520 Removing and installing camshafts Overhaul
3. Take hydraulic tappets out of the cylinder head and lay them on a clean surface, arranged according to cylinders and valves. Do not interchange components. For details, see -> 155920 Removing and installing valve lifters (hydraulic tappets) Service and Repair
Information
Component overview
In the Turbo, the exhaust valve is fitted with internal and external valve springs (set of valve springs) and adapted concave washers. The exhaust valve in the turbo engine has the same outer dimensions as the exhaust valve of the naturally aspirated engine. However, because of the sodium filling, the exhaust valve in the turbo engine is lighter and the shank over the shank entries is longer. For further details, please see Figures and Table entitled "Valve dimensions".
Valves (Figure, turbo cylinder bank 5 to 8)
Distinguishing features of exhaust valve on naturally aspirated and turbo engine
Difference between exhaust valve on naturally aspirated and turbo engine
Special tools
Special tools for valve
Valve dimensions
Removing valves
Information
- Secure the cylinder head on a level surface, which allows easy access to the valves from underneath.
- No valves should be hidden by the surface under the cylinder head.
- The cylinder head fastening must not tip over when tools are used.
1. Before removing the valves, remove the spark plugs and screw in the valve lock => Screwing in tool. The valve lock prevents the valves from opening when they are pressed down. Alternatively, a rubber plate placed underneath helps on a level cylinder head surface -2-.
Screwing in tool
Locking valves
2. Fit and set the tool on the cylinder head.
2.1. Screw a holder -1- with a suitable thread into the matching thread on the cylinder head. The hook -2- is pre-fitted in the holder.
Fitting hook
2.2. Insert a suitable plastic guide -1- instead of the cam follower.
Inserting plastic guide
2.3. Insert assembly cartridge -1- for the valve keys into the plastic guide.
Inserting assembly cartridge
2.4. Engage a lever (assembly fork) -1- into the hook and position it correctly on the assembly cartridge. Make sure that the tool and equipment can work straight.
Tool fitted correctly
3. Remove the valve keys.
3.1. Press the assembly cartridge down against the valve spring force using a lever (assembly fork) and keep it pressed => Pressing down tool. The knurled screw on the assembly cartridge moves forward -1-.
Pressing down tool
Pressing down lever and knurled screw
Information
The mechanic must practice for use of the assembly cartridge to be effective. Some repetitions must be made to ensure that the valve keys are correctly held in place.
3.2. Turn the knurled screw back and forward -1- so that the valve keys engage and are held in the assembly cartridge -2-. The knurled screw moves back again.
Turning knurled screw back and forward
3.3. Remove the assembly cartridge and check that the two valve keys are positioned correctly -1-.
Valve keys in assembly cartridge
3.4. Pull the knurled screw on the assembly cartridge -1- and disengage the valve keys -2-.
Removing valve keys
4. Remove valve springs, spring plate and valve keys from the cylinder head.
5. Remove valve locks and push the valves to the side of the combustion chamber.
Installing valves
NOTICE
Valve grinding paste not removed
- Risk of damage to sealing face on intake valve
-> Remove all valve grinding paste fully after grinding.
Information
- The valves cannot be touched up afterwards.
- The valves can be ground using commercially available valve grinding paste.
1. Apply a small a fit of valve grinding paste to the valve seat.
2. Oil the valve stem of a new valve and insert it into the valve guide from the combustion chamber. Push the valve in until it is seated securely in the valve seat of the cylinder head.
3. Grind down the valve with a commercially available valve grinder (with a rubber suction cup) using rotating movements. To do this, grip the valve grinder between the palms of your hands and press it against the valve seat in rotating movements => Grinding the valve seat.
Grinding the valve seat
4. Carry out the grinding operation for each valve that is replaced. Check for leaks using some fuel and installed spark plugs. The fuel must not escape through the valve seat. Carefully remove valve grinding paste.
5. Fit valve lock => Locking valves
Locking valves
6. Replace valve stem seals. For details, see -> 156355 Replacing valve stem seals Service and Repair
7. Fit valve springs, concave washer and valve keys. To do this, place valve springs (there are two in the exhaust valve in the turbo engine) on the bottom concave washer. Place top concave washer in position.
Information
The mechanic must practice for use of the assembly cartridge to be effective. Some repetitions must be made to ensure that the valve keys are correctly held in place.
8. Insert the valve keys into the assembly cartridge.
8.1. Press the spring-tensioned washer of the assembly fixture down -1- and insert the valve keys -2- with the narrow end down.
Valve key in assembly fixture
8.2. Ensure that the valve keys fit symmetrically and are inserted as far as they will go in the tool. The spring-tensioned washer automatically locks the valve keys in place.
8.3. Position the assembly cartridge -2- so that it is centered on the assembly fixture. Observe installation position of the valve keys -1-.
Fitting assembly cartridge
8.4. Press the assembly cartridge against the spring force onto the assembly fixture. The knurled screw moves forward. Turn the knurled screw back and forward until the valve keys engage. Repeat this several times if necessary. => Assembly cartridge grips the valve keys
Assembly cartridge grips the valve keys
8.5. Check that the valve keys are held symmetrically in the assembly cartridge -1-.
Valve keys inserted
9. Place the valve key assembly cartridge onto the cylinder head (same as removal of valve) and position it on the top spring plate.
10. Press the assembly cartridge down against the valve spring force using a lever (assembly fork) and keep it pressed. The knurled screw moves forward. Turn the knurled screw back and forward until the valve keys engage => Installing valve keys. Repeat this several times if necessary.
Installing valve keys
11. When installing the valve keys, check that they are positioned correctly.
Subsequent work
1. Install cylinder head. -> 157019 Removing and installing cylinder head Service and Repair
2. Fit hydraulic tappets. Do not interchange components. -> 155920 Removing and installing valve lifters (hydraulic tappets) Service and Repair
3. Install camshafts. -> 150520 Removing and installing camshafts Overhaul