156120 Removing and Installing Valve on 4.8-Litre DFI Engines
WM 156120 Removing and installing valve on 4.8-litre DFI engines
Tools
Preliminary work
1. Remove cylinder head. -> 157019 Removing and installing cylinder head on 4.8-litre DFI engines 157019 Removing and installing cylinder head on 4.8-litre DFI engines
2. Remove the camshafts. -> 150520 Removing and installing camshafts on 4.8-litre DFI engines 150520 Removing and installing camshafts on 4.8-litre DFI engines
3. Take hydro-tappets out of the cylinder head and lay them on a clean surface, arranged according to cylinders and valves. Do not confuse components. For details, see -> 155920 Removing and installing hydro-tappets on DFI engines Removal and Replacement
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 feature 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. The spark plugs must be removed and the valve lock screwed in before the valves are removed => Screwing in tool. The valve lock prevents the valves from being opened while being pressed down. Alternatively, a rubber plate placed underneath helps if the cylinder head surface is smooth -2-.
Screwing in tool
Locking valves
2. Fit and set the tool on the cylinder head
2.1. Screw -1- a holder with the appropriate thread into its matching thread on the cylinder head. The hooking piece -2- is pre-fitted in the holder.
Fit the hook
2.2. Insert the appropriate plastic guide -1- in place of the tappet.
Insert plastic guide
2.3. Insert assembly cartridge -1- for the valve keys into the plastic guide.
Insert assembly cartridge
2.4. Hook the lever (assembly bar) -1- into the hook and place correctly onto the assembly cartridge. Make sure that the tool and equipment can be effective directly.
Correctly fit the tool
3. Remove the valve keys
3.1. Press the assembly cartridge with the lever (assembly bar) against the force of the valve-spring and keep pressed => Press down the tool. The knurled screw of the assembly cartridge pushes forward -1-.
Press down the tool
Press down the 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 forth -1- until the valve keys snap into place and are held there -2- in the assembly cartridge. The knurled screw retracts.
Turn the knurled screw back and forth
3.3. Remove the assembly cartridge and check correct position of both valve keys -1-.
Valve keys in assembly cartridge
3.4. Pull out the knurled screw from the assembly cartridge -1- and knock out the valve keys -2-.
Remove the 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 in the valve using the commercially available valve grinding tool (with rubber suction cup) by means of rotary movements. To do this, hold the valve grinder between the palms of both hands and press against the valve seat with 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. Details at -> 156319 Removing and installing valve-stem seals on 4.8-litre DFI engines 156319 Removing and Installing Valve-Stem Seals on 4.8-Litre DFI Engines
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 valve keys into the assembly cartridge.
8.1. Press the spring washer of the assembly fixture downwards -1- and insert the valve key -2- with the narrow end pointing downwards.
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 washer automatically locks the valve keys in place.
8.3. Place the assembly cartridge -2- onto the centre of the assembly fixture. Observe installation position of the valve keys -1-.
Fit the assembly cartridge
8.4. Press the assembly cartridge against the spring force onto the assembly fixture. The knurled screw moves forward. When doing so, turn the knurled screw back and forth until the valve keys snap into place. Repeat as required. => Assembly cartridge accepts the valve keys
Assembly cartridge accepts the valve keys
8.5. Make sure the valve keys are held symmetrically in place 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 with the lever (assembly bar) against the force of the valve-spring and keep pressed. The knurled screw moves forward. When doing so, turn the knurled screw back and forth until the valve keys snap into place => Install valve keys. Repeat as required.
Install valve keys
11. When installing the valve keys, check their correct positioning.
Subsequent work
1. Install cylinder head. -> 157019 Removing and installing cylinder head on 4.8-litre DFI engines 157019 Removing and installing cylinder head on 4.8-litre DFI engines
2. Install hydro-tappets. Do not confuse components. -> 155920 Removing and installing hydraulic tappets on DFI engines Removal and Replacement
3. Install camshafts. -> 150520 Removing and installing camshafts on 4.8-litre DFI engines 150520 Removing and installing camshafts on 4.8-litre DFI engines