Overhaul
WM 158220 Removing and installing cylinder head cover - engine removed
Preliminary work
Preliminary work
1. Remove engine.
Removing cylinder head cover
Removing cylinder head cover on M97.20 and M97.21
Caution
Risk of damage due to particles of dirt.
^ Danger of material damage due to blocked oil bores/oil ducts.
-> Absolute cleanliness is essential when working on the engine.
-> Lay removed engine parts on a clean base and make sure to cover them.
-> Use the cover for dust protection when fitting the engine NR.165 on the engine assembly support.
Note
The coated screws for the bearing surfaces of the camshaft in the cylinder head cover must be replaced when installing.
Note
Replace O-ring on the oil suction pump or tandem pump.
Cylinder bank 1-3:
1. Disconnect oil pressure switch cable plug.
2. Disconnect and remove cable plugs for ignition coils. Remove ignition coils -1-. To do this, unscrew each of the two Torx screws (M6 x 25) and remove the ignition coils from the spark-plug recess.
3. Remove holder and retainer plates (with integrated seal) for the solenoid hydraulic valves (camshaft adjustment and valve lift control) -2-.
If the valves do not have to be replaced, these can remain in the cylinder head (side 1-3 both, side 4-6 camshaft adjustment only).
3.1. Replace retainer plate (with integrated seal) during assembly.
4. If the solenoid hydraulic valve for camshaft adjustment is removed, the oil strainer -1- must be checked for damage and contamination, and replaced if necessary.
5. Remove oil suction pump 1-3. Unscrew four M6 x 20 Torx screws (micro-self-locking), remove oil suction pump, replace O-ring and screws.
6. Unclip oxygen sensor line from the brackets.
Caution
Damage when levering off the cylinder head cover.
^ Cast lugs could break.
-> Perform work steps carefully and gently.
7. Remove cylinder head cover. Unscrew 20 M6 x 30 Torx screws from the cylinder head cover. To loosen the cylinder head cover, raise the cover carefully at the two protruding cast edges with a screwdriver or mounting lever. Remove cylinder head cover.
8. Remove the plastic caps.
Note
Make sure that it is cleaned thoroughly and that residual sealing compound is removed completely. Even the smallest particles can block up oil bores.
9. Clean the sealing faces on the cylinder head cover and cylinder head thoroughly (use a brass or nylon brush, a clean and lint-free cloth soaked in acetone). All residual sealing compound in the cylinder head and on the cover must be removed before assembly.
Additional work steps on cylinder bank 4-6:
- A tandem pump is installed on side 4-6 instead of the oil suction pump. Pull off the vacuum line on the pump -2-. Replace O-rings and micro-self-locking screws -1-.
Installing cylinder head cover
Installing cylinder head cover on M97.20 and M97.21
Caution
Risk of damage due to particles of dirt.
^ Danger of material damage due to blocked oil bores/oil ducts.
-> Absolute cleanliness is essential when working on the engine.
-> Lay removed engine parts on a clean base and make sure to cover them.
-> Use the cover for dust protection when fitting the engine NR.165 on the engine assembly support.
Note
The coated screws for the bearing surfaces of the camshaft in the cylinder head cover must be replaced when installing.
1. Insert three new seals for the spark-plug recesses.
Only the following sealants may be used to seal the cylinder head cover:
^ "Drei Bond" silicone - type 1209
^ Loctite 5900
2. Prepare cylinder head cover for assembly. Apply a thin bead of sealant on the cylinder head cover (not more than 1.5 mm high).
3. Coated screws on the camshaft bearing surfaces -1- must be replaced.
4. Place the cylinder head cover carefully onto the cylinder head. The bead of sealing compound must not be wiped off or broken.
5. Position 20 Torx screws (eight of these should be new, coated screws -1-4 and 7-10-) on the cylinder head cover and tighten according to the specified tightening sequence. Only lightly screw in the two screws in the area of the oil suction pump/tandem pump. They will be tightened after the pump is assembled.
-> Tightening torque: 13 Nm (9.5 ftlb.)
6. Position a new cap diameter 45 mm (brown) on the bore of the inlet camshaft on the pulley side and tap it gently into place with a plastic hammer (dry mount).
7. Insert two new caps (green) into the small bores on the clutch side. Tap them in with a plastic hammer (dry mount).
Note
Replace O-ring on the oil suction pump or tandem pump.
8. Mount the oil suction pump or tandem pump with four new, micro-self-locking Torx screws -1-. Replace O-rings on the pumps and the vacuum line -2-. Lightly grease O-rings with Optimol MP3.
9. Tighten the two screws on cylinder head cover in area of oil suction pump/tandem pump.
-> Tightening torque: 13 Nm (9.5 ftlb.)
10. Push new retainer plates (with integrated seal) onto solenoid hydraulic valves. Position holder and tighten with two Torx screws (M6 x 20).
A - Holder for camshaft adjustment valve
B - Holder for valve lift adjustment valve
1 - Camshaft adjustment retainer plate
2 - Valve lift adjustment retainer plate
11. Insert ignition coils into the spark-plug recesses. Position and tighten two M6 x 25 Torx screws per ignition coil.
-> Tightening torque: 10 Nm (7.5 ftlb.)
12. Plug in cable plugs for ignition coils and solenoid hydraulic valves. Clip the cables of the hydraulic valves into the brackets.
13. Connect cable plug to oil temperature switch.
14. Clip oxygen sensor lines into brackets.