Part 1

11 31 001 - Replacing camshaft (M52TU/M54/M56)





Special tools required:
- 00 9 250 00 9 250 Torque Wrench with Flexible Extension
- 11 2 300 11 2 300 Plug Mandrel
- 11 3 240 11 3 240 Locking Fixture
- 11 3 244 11 3 240 Locking Fixture
- 11 3 250 11 3 250 Suction Cup
- 11 3 260 11 3 260 Fixture
- 11 3 292
- 11 4 220 11 4 220 Chain Tensioner
- 11 6 150 11 6 150 Adjusting Plate
- 11 6 180 11 6 180 Fixture

(if necessary inlet or exhaust side)

The inlet or exhaust camshaft can be replaced in the vehicle.





Important!
Incorrect assembly/removal without special tools exposes the camshaft to the risk of preliminary damage or breakage. The valves may also be bent by contact with the piston crown. Comply without fail with the job instructions, recommended special tools and work sequence.





Removal

Removal of camshafts is described separately from installation. The assembly sequence for removal and installation is different.

Remove VANOS adjustment unit Service and Repair.





Important!
Cylinder for chain tensioning piston is under spring pressure.

Unfasten cylinder for chain tensioning piston.





Press down secondary chain tensioner at top and lock with special tool 11 3 292.





Release nuts, remove sensor gear (1).





Remove plate spring (2).





Release nuts on inlet side and remove corrugated washer (7).





Unfasten screws.





Lift off exhaust and inlet chain wheels together with chain, friction washer (3) and toothed shaft (4).

Note:
Toothed shaft (4) is and identical part for exhaust and inlet sides. Store used toothed shafts in order and reinstall on the same side only.





Remove toothed shaft (5) with toothed sleeve (6).





Unfasten screws. Remove secondary chain tensioner.





Release screw-in pin.





Feed chain wheel (1) towards front out of timing chain (2).





Note:
Timing chain remains positioned over exhaust camshaft.





If necessary, release screw-in pin on inlet side.

Remove thrust washer.





Remove sensor gear.





Important!
Do "not" release these screws.





Unscrew studs.





Pull special tool 11 2 300 11 2 300 Plug Mandrel back until flywheel is no longer secured in position.





Important!
To prevent damaging valves when fitting the camshafts, no pistons should be in TDC position.

Lift timing chain and hold under tension.

Rotate engine against direction of engine rotation approx. 30° using the central bolt.





Important!
Bearing cap 1 of inlet camshaft is centered with adapter sleeves.

To prevent inlet camshaft from tilting in bearing strip, release nuts and remove bearing cap 1.





Fit special tool 11 3 260 11 3 260 Fixture to cylinder head and screw into spark plug threads in cylinders 1 and 4.





Turn the eccentric shaft to tension the bearing caps.

Unfasten nuts on bearing cover.





Relieve tension on eccentric shaft and remove special tool 11 3 260 11 3 260 Fixture.

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





Note:
If the cylinder head is then to be removed, remove complete bearing strip with bucket tappets.

Locate bucket tappets in bearing strip with special tool 11 3 250 11 3 250 Suction Cup.

Lift out complete bearing strip with bucket tappet.

Note:
Only re-use used bucket tappets in the same tappet bore.





Check bearing points on bucket tappets for signs of wear (scoring).





Bearing strips are marked "A" for exhaust side and "E" for inlet side.





Note centering dowels on retaining pins at bearing points 2 and 7.

Install bearing strips.





Installation

Installation of camshafts is described separately from removal. The assembly sequence for removal and installation is different.

Note:
Camshafts, bearings and bearing caps, friction washers, all splines on toothed shafts and spline hubs must be oiled before installation.





Important!
The bucket tappets expand when not subjected to load by the camshaft and therefore require some time before they can be pushed back down. During a rapid assembly sequence, the "closed" valves may still be open and be in contact with the piston.





Comply with following waiting periods after installing camshaft and before cranking engine back to TDC position.

- Room temperature (20 °C) 4 mins
- 10 °C ... 20 °C 11 mins
- 0 °C ... 10 °C 30 min





Pull up timing chain and feed in exhaust camshaft.

Position timing chain on exhaust camshaft.





Install camshafts so that cam tips on inlet and exhaust valves on 1st cylinder face one another.





Fit bearing cover.

Note:
Bearing caps are marked from exhaust side:



A1 ... A7 for exhaust side
E1 ... E7 for inlet side





Fit special tool 11 3 260 11 3 260 Fixture to cylinder head and screw into spark plug threads in cylinders 1 and 4.





Turn the eccentric shaft to tension the bearing caps.

Tighten down bearing cover.

Tightening torque, 11 31 1AZ 11 31 Camshaft.

Remove special tool 11 3 260 11 3 260 Fixture.





Important!
Do not damage the cylinder head.

If necessary, machine open-end wrench accordingly.

Align camshafts with open-end wrench.





Fit special tool 11 3 240 11 3 240 Locking Fixture to camshafts on cylinder 6. Align camshafts so that special tool 11 3 240 11 3 240 Locking Fixture rests without gaps on cylinder head.





Attach special tool 11 3 244 11 3 240 Locking Fixture to special tool 11 3 240 11 3 240 Locking Fixture and locate by way of spark plug thread.





Lift timing chain and hold under tension.

Turn engine from 30° before TDC position in direction of rotation as far as TDC position.





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

Important!
Remove special tool 11 2 300 11 2 300 Plug Mandrel before starting engine.

Continued in Part 2.