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.

Information
The coated screws for the bearing surfaces of the camshaft in the cylinder head cover must be replaced when installing.

Information
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- and.

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.





Hydraulic valves for camshaft adjustment and ignition coils

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.





Oil strainer in hydraulic valve for camshaft adjustment

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.





Oil suction pump 1 - 3

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.





Lifting cylinder head cover from above





Lifting cylinder head cover from below

8. Remove the plastic caps.

Information
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-.





Tandem pump side 4-6