11 31 001Replacing camshaft (M50) (intake or exhaust side as applicable)

Lift engine hood into assembly position and remove firewall (air manifold). This work is described in section on removing complete wiper console,

refer to 61 61 270

Remove complete air guide for alternator.
Caution!

Left-hand threads.


Using special tool 11 5 030, brace against pulley and unfasten cap nut from water pump using special tool 11 5 040.

Unfasten fan shroud, take fan wheel with fan clutch off water pump and remove with fan shroud.

Tightening Torque,

refer to Technical Data 11 52 1AZ

Unfasten screws (1 and 2).

Pull off connecting strip.

Caution!

Watch out for rubber seals.


Removing cylinder head cover,

refer to 11 12 000

Remove sensor.Installation:

Check/replace sealing ring.


Remove cable channel.
Unscrew suspension eye and upper timing case cover.
Installation:

Replace seal.

Check dowel sleeves.


Pull off cover.
Remove camshaft Caution!

Incorrect removal/installation without help of fixture could damage or break the camshaft. Valves could also be bent through contact with the piston crowns. Always note installation instructions and use specified special tools, procedures, and sequences.


Removal

The removal of the camshaft is described separately from the installation. Assembly sequence for removal and installation is different.

Rotate engine in rotation direction, until cam tips of intake and exhaust camshafts point to each other at 1st cylinder.

Arrows on sprockets face up.

Press down chain tensioner at top and lock by inserting special tool 11 3 290.

Remove the chain wheels.

Lift off both sprockets complete with chain.

Remove sensor gear for pulse sensor from intake camshaft.
Unscrew secondary chain tensioner.
Unscrew chain guide.
Caution!

Strong spring force.


Unfasten screw plug (3) from chain tensioner.

Remove spring (2) and piston (1).

Lift off sprocket with chain.
Caution!
Secure timing chain from slipping downward.

Caution!

To prevent the valves from being damaged during installation of the camshaft, the pistons may not be in the TDC position.

Rotate engine counter-enginewise approx. 30° using the central screw.


Unscrew studs.
Screw special tool 11 3 260 and special tool 11 3 270 together.

Remove spark plugs.

Position special tool 11 3 260 and screw into spark plug threads.

Tightening Torque 23 Nm

Apply pressure on bearing caps by turning the eccentric shaft.

Unfasten all nuts for bearing cover.

Loosen eccentric shaft and remove special tool 11 3 260.

Remove bearing covers and place to one side in orderly fashion. Remove camshaft.

If necessary, remove complete bearing strip with bucket tappets.

Brace bucket tappets with special tool 11 3 250.

Lift out complete bearing strip with bucket tappet.

Note:

Worn bucket tappets may only be reused in the same tappet bore.


Check tappet bores for wear (scoring).
Note:
The bearing strips are marked with "A" for exhaust side and "E" for intake side.

Check centering sleeves on studs of bearings 2 and 7.

Install bearing strips.

Note:
Identification of camshafts through difference on flange for sprockets:

E = Intake camshaft
A = Exhaust camshaft

Installation

The installation of the camshaft is described separately from the removal. Assembly sequence for removal and installation is different.

Caution!
The bucket tappets expand when not subjected to load by the camshaft and therefore require some time before they can be pushed back down. As a result, even the ”closed” valves can still be open and located at the piston during a rapid assembly sequence.

You must adhere to the following waiting periods after installing the camshaft and before cranking the engine back to the TDC position.
  • Room temperature (20°C) 4 mins
  • 10°C ... 20°C 11 mins
  • 0 °C ... 10 °C 30 mins.
Fit camshaft and position bearing cover.Note:

The bearing covers are clearly marked and can be read from the exhaust end:


A1 ... A7 for the exhaust end
E1 ... E7 for the intake end

Position special tool 11 3 260 and screw into spark plug threads.

Tightening Torque 23 Nm

Apply pressure on bearing caps by turning the eccentric shaft.

Fit all nuts for bearing cover and tighten.

Tightening Torque,

refer to Technical Data 11 31 1AZ

Remove special tool 11 3 260.

Caution!

Make sure that bearing banks are not damaged.


Machine open-end wrench accordingly if necessary.

 

Align camshafts so that the cam tips of the intake and exhaust camshaft point toward each other at the 1st cylinder.
Align camshafts and secure with special tool 11 3 240.Note:

Camshaft setting is OK if special tool 11 3 240 can lie flush on the cylinder head.


Rotate engine from the 30° before TDC position engine-wise up to TDC position.

Secure crankshaft in TDC position with special tool 11 2 300.

Caution!

Remove special tool 11 2 300 before switching on the engine.


Lay timing chain on sprocket. Arrow on sprocket faces up.

Fit sprocket to exhaust camshaft with threaded bores on left side aligned down the deep bores.

Align groove on chain tensioning piston vertical to clamping rail.

Replace sealing ring of sealing plug (3).

Install piston (1), spring (2) and sealing plug (3).

Tightening Torque of sealing plug (3),

refer to Technical Data 11 31 8AZ

Note:
The longitudinal sprocket holes are now centered to the threaded bores.

Install chain guide.
Install secondary chain tensioner.
Fit sensor gear for impulse sensor to intake camshaft.

Mount both sprockets together with chain.

Note:

Arrows on sprockets point upwards.


Align long bores centrally.

Insert bolts and fit clearance-free, but do not tighten yet.
Remove special tool 11 3 290.

Pretighten both chain sprockets, starting on the intake side with approx. 5 Nm and then tighten in a second pass.

Tightening Torque,

refer to Technical Data 11 31 3AZ

Remove special tool 11 3 240.

Remove special tool 11 2 300.

Rotate engine in direction of rotation twice, then check camshaft adjustment. Disconnect engine with special tool 11 2 300, fit special tool 11 3 240.

Note:

Camshaft setting is OK if special tool 11 3 240 can lie flush on the cylinder head.

Assemble engine.


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