Timing Chain: Service and Repair
Installing camshaft - engine removed - includes adjusting timing, - as of MY 2002Engine type M 96/03
Caution: When working on the engine, absolute cleanliness is essential! An engine cover should be used on the engine assembly support. Lay removed engine parts on a clean base and cover them without fail. Even the smallest particles of dirt can block up oil bores.
Requirements
- Engine completed except for the cylinder heads
- Flat-base tappet housing installed
Installing camshafts - cylinder bank 4 - 6
1. In order to remove the play from the control chain drive, turn the engine at the belt pulley of the crankshaft clockwise (engine direction of rotation) to 60° before TDC (identification U6 on the belt pulley is flush with the fixing bore in the crankcase). Fix with the special tool fixing pins as of mod. 98 9595/1. Use short fixing pin.
2. Turn the engine at the assembly support until cylinder bank 4-6 stands vertically upwards.
Caution: Flat-base tappets have been run in the fitting bores and must be inserted again in their original position (allocation). For oiling, only use new engine oil.
3. Install flat-base tappets, side 4-6. Coat the tappets with new engine oil and insert them according to the relevant allocation for each cylinder (as removed). Make sure that the dowel pins of the inlet stroke tappets are flush with the bores in the housing -arrow-.
4. Oil the bearing surfaces of the camshafts with new engine oil.
5. Insert inlet camshaft 4-6. If necessary, pre-assemble the inlet camshaft. Pull the control chain out of the chain housing of the cylinder head with a welding wire and position on the toothed ring of the camshaft adjuster, at the same time inserting the camshaft at overlapping TDC of cylinder 4 (the cams of cylinder 4 point towards the bulkhead of the flat-base tappet housing -arrows- ).
Note;
- Make sure that the bearing sleeve of the inlet camshaft is positioned correctly.
6. The bearing sleeve of the inlet camshaft must be positioned so that the centrally bored blind hole points vertically upwards (the rib of the cylinder head should also be at the centre in relation to the bearing sleeve). In this position, the dowel pin in the bearing bore of the cylinder head will fit precisely into the opposite off-centre blind hole bore. Any other bores are through-holes for guiding the oil.
7. Insert exhaust camshaft 4-6. Lay the control chain on the flange for the chain sprocket, then insert the camshaft at overlapping TDC of cylinder 4 (the cams of cylinder 4 point towards the cams of the inlet camshaft -arrows- ).
8. Install the chain sprocket of the exhaust camshaft. Insert the chain sprocket in the control chain, then position on the camshaft flange. The four threaded bores in the camshaft flange must be approximately half covered to the right by the slots of the chain sprocket in the engine direction of rotation.
Note;
- Do not interchange the thrust bearings of the inlet and exhaust camshafts during assembly. Observe the identification (Figure shows inlet camshaft bearings).
- Designation of inlet camshaft bearing: thrust bearing: E and pairing number on cylinder head/cylinder head cover, bearing cover of the bearing sleeve: only pairing number.
- Designation of exhaust camshaft bearing: thrust bearing on chain sprocket: 1A and pairing number on cylinder head/cylinder head cover, 2nd thrust bearing: 2A and pairing number on cylinder head/cylinder head cover.
9. Insert three thrust bearings and one bearing cover for the bearing sleeve of the camshafts with the guide rail for the control chain. Eight hexagon socket bearing screws: position six M6 x 35 (Item 1) and two M6 x 40 (Item 2) screws for the camshaft bearings and the guide rail and tighten slightly.
Position of the bearing screws: Item 1 = M6 x 35, Item 2 = M6 x 40
Adjusting timing, side 4 - 6
1. Align camshafts. On both camshafts, the smaller circular cutouts must lie at the top -arrows-.
2. Fix the camshafts with special tool adjustment gauge 9686 and fasten the gauge with one M8 auxiliary screw (e.g. M8 x 16 hexagon-head bolt) (flat tool surface should face upwards). Only tighten the screw slightly.
3. Screw the bearing cover screws of the inlet and exhaust camshafts and the auxiliary screw of the adjustment gauge alternately by another approximately 90° until the specified tightening torque of 10 Nm (7.5 ft. lbs.) is reached.
Tightening torque: 10 Nm (7.5 ft. lbs.)
4. Insert the guide rail screw with a new O-ring and tighten. Hexagon socket M6, a/f 5.
Tightening torque: 10 Nm (7.5 ft. lbs.)
5. Fit the chain tensioner, side 4-6 (hexagon socket a/f 14). Replace sealing ring. Position the chain tensioner with new sealing ring and tighten with a torque wrench.
Tightening torque: 80 Nm (59 ft. lbs.)
Note;
- Move the engine at the belt pulley of the crankshaft to the TDC marking without fail.
6. Turn the engine at the belt pulley of the crankshaft clockwise (engine direction of rotation) to the TDC marking (the TDC bore in the belt pulley is flush with the fixing bore in the crankcase). Fix with the special tool fixing pins as of mod. 98 9595/1. Use short fixing pin.
7. Position the four M6 x 12 hexagon-head bolts for the chain sprocket of the exhaust camshaft and tighten crosswise with a torque wrench.
Tightening torque: 14 Nm (10.5 ft. lbs.)
8. Tighten the central screw of the camshaft adjusting device. Position special tool retaining tool 9685 on the adapter of the central screw and place the loose contact block at the fitting bore of the oil extraction pump. Tighten the hexagon-head bolt on the contact block.
9. Tighten the central screw in two stages.
First stage: pre-tightening torque: 50 Nm (37 ft. lbs.).
Note;
- Before the final tightening of the central screw, remove special tool adjustment gauge 9686 without fail.
10. Remove special tool adjustment gauge 9686. Unscrew the M8 auxiliary screw and pull off the gauge.
Second stage: final tightening of central screw: 110° torque angle with torque angle wrench.
11. Insert two magnetic hydraulic valves and three seals for the spark-plug recesses. Fit new O-rings into both the magnetic hydraulic valves and insert into the bores in the cylinder head. (Camshaft adjustment with dowel pin, valve lift control without dowel pin). Replace the three seals for the spark-plug recesses.
12. Install cylinder head cover.
13. Fit both holders (A and B) and two new covers for the magnetic hydraulic valves for Vario-Cam Plus. Push two new covers (identical parts) over the valves and position and tighten two holders with two M6 x 20 hexagon socket head bolts each.
- A: Holder for camshaft adjustment valve
- B: Holder for valve lift adjustment valve
Cover for magnetic hydraulic valves in installation position with integrated seal
- 1 : Camshaft adjustment valve (control chain side)
- 2 : Valve lift adjustment valve
Tightening torque: 10 Nm (7.5 ft. lbs.)
14. Install ground strap on cylinder head. Position and tighten M8 x 20 hexagon-head bolt.
Tightening torque: 23 Nm (17 ft. lbs.)
15. Install ignition coils. Insert three ignition coils in the spark-plug recesses, position and then tighten two M6 x 25 hexagon socket head bolts.
Tightening torque: 10 Nm (7.5 ft. lbs.)
16. Install holder for the main muffler. Insert holder from the belt pulley side, position two M8 x 30 hexagon-head bolts at the top and two M8 x 25 hexagon-head bolts at the bottom and tighten. Connect the electrical plug of ignition coil cylinder 5 and the two electrical plugs of the magnetic hydraulic valves, then fasten the cable in the sheetmetal brackets.
Tightening torque: 23 Nm (17 ft. lbs.)
17. Install the shield. Insert the shield, position and tighten the two M6 x 16 hexagon-head bolts.
Tightening torque: 10 Nm (7.5 ft. lbs.)
18. Connect the two cable plugs on the oil temperature switch.
19. Turn the engine at the assembly support by approximately 90° until the engine is horizontal (intake system at the top).
Installing camshafts - cylinder bank 1 - 3
1. In order to remove the play from the control chain drive, turn the engine at the belt pulley of the crankshaft clockwise (engine direction of rotation) to 60° before TDC (identification U6 on the belt pulley is flush with the fixing bore in the crankcase). Fix with the special tool fixing pins as of mod. 98 9595/1. Use short fixing pin.
2. Turn the engine at the assembly support until cylinder bank 1-3 stands vertically upwards.
Caution: Flat-base tappets have been run in the fitting bores and must be inserted again in their original position (allocation). For oiling, only use new engine oil.
3. Install flat-base tappets, side 1-3. Coat the tappets with new engine oil and insert them according to the relevant allocation for each cylinder (as removed). Make sure that the dowel pins of the inlet stroke tappets are flush with the bores in the housing -arrow-.
4. Oil the bearing surfaces of the camshafts with new engine oil.
5. Insert inlet camshaft 1-3. If necessary, pre-assemble the inlet camshaft. Pull the control chain out of the chain housing of the cylinder head with a welding wire and position on the toothed ring of the camshaft adjuster. Then insert the camshaft at overlapping TDC of cylinder 1 (the cams of cylinder 1 point diagonally downwards towards the outside of the cylinder head -arrow- ).
Note;
- Make sure that the bearing sleeve of the inlet camshaft is positioned correctly.
6. The bearing sleeve of the inlet camshaft must be positioned so that the centrally bored blind hole points vertically upwards (the rib of the cylinder head should also be at the centre in relation to the bearing sleeve). In this position, the dowel pin in the bearing bore of the cylinder head will fit precisely into the opposite off-centre blind hole bore. Any other bores are through-holes for guiding the oil.
7. Insert exhaust camshaft 1-3. Lay the control chain on the flange for the chain sprocket, then insert the camshaft at overlapping TDC of cylinder 1 (the cams of cylinder 1 point diagonally downwards towards the outside of the cylinder head -arrows- ).
8. Install the chain sprocket of the exhaust camshaft. Insert the chain sprocket in the control chain, then position on the camshaft flange. The four threaded bores in the camshaft flange must be fully visible on the left at the slot curves of the chain sprocket, so that the four M6 x 12 hexagon-head bolts can still be positioned to fasten the chain sprocket.
All four screws positioned on the chain sprocket, side 1-3
Note;
- Do not interchange the thrust bearings of the inlet and exhaust camshafts during assembly. Observe the identification (Figure shows inlet camshaft bearings).
- Designation of inlet camshaft bearing: thrust bearing: E and pairing number on cylinder head/cylinder head cover, bearing cover of the bearing sleeve: only pairing number.
- Designation of exhaust camshaft bearing: thrust bearing on chain sprocket: 1A and pairing number on cylinder head/cylinder head cover, 2nd thrust bearing: 2A and pairing number on cylinder head/cylinder head cover.
9. Insert three thrust bearings and one bearing cover for the bearing sleeve of the camshafts with the guide rail for the control chain. Eight hexagon socket bearing screws: position six M6 x 35 (Item 1, lower illustration) and two M6 x 40 (Item 2, lower illustration) for the camshaft bearings and the guide rail and tighten slightly.
Position of the bearing screws: Item 1 = M6 x 35, Item 2 = M6 x 40
Adjusting timing, side 1 - 3
1. Align camshafts. On both camshafts, the smaller circular cutouts must lie at the top -arrows-. If necessary, shift the camshafts slightly.
2. Fix the camshafts with special tool adjustment gauge 9686 and fasten the gauge with one M8 auxiliary screw (e.g. M8 x 16 hexagon-head bolt) (flat tool surface should face upwards). Only tighten the screw slightly.
3. Screw the bearing cover screws of the inlet and exhaust camshafts and the auxiliary screw of the adjustment gauge alternately by another approximately 90° until the specified tightening torque of 10 Nm (7.5 ft. lbs.) is reached.
Tightening torque: 10 Nm (7.5 ft. lbs.)
4. Fit the chain tensioner, side 1-3 (hexagon socket a/f 32). Replace sealing ring. Position the chain tensioner with new sealing ring and tighten with a torque wrench.
Tightening torque: 80 Nm (59 ft. lbs.)
Note;
- Move the engine at the belt pulley of the crankshaft to the TDC marking without fail.
5. Turn the engine at the belt pulley of the crankshaft clockwise (engine direction of rotation) to the TDC marking (the TDC bore in the belt pulley is flush with the fixing bore in the crankcase). Fix with special tool fixing pins as of mod. 98 9595/1. Use short fixing pin.
6. Tighten the four M6 x 12 hexagon-head bolts for the chain sprocket of the exhaust camshaft crosswise with a torque wrench.
Tightening torque: 14 Nm (10.5 ft. lbs.)
7. Tighten the central screw of the camshaft adjusting device. Position special tool retaining tool 9685 on the adapter of the central screw and place the loose contact block at the fitting bore of the oil extraction pump. Tighten the hexagon-head bolt on the contact block.
8. Tighten the central screw in two stages.
First stage: pre-tightening torque: 50 Nm (37 ft. lbs.).
Note;
- Before the final tightening of the central screw, remove special tool adjustment gauge 9686 without fail.
9. Remove special tool adjustment gauge 9686. Unscrew the M8 auxiliary screw and pull off the gauge.
Second stage: final tightening of central screw: 110° torque angle with torque angle wrench.
10. Replace the three seals for the spark-plug recesses.
11. Install the cylinder head cover.
12. Fit both holders (A and B) and two new covers for the magnetic hydraulic valves for Vario-Cam Plus. Push two new covers (identical parts) over the valves and position and tighten two holders with two M6 x 20 hexagon socket head bolts each.
- A: Holder for camshaft adjustment valve
- B: Holder for valve lift adjustment valve
Cover for magnetic hydraulic valves in installation position with integrated seal
- 1 : Camshaft adjustment valve (control chain side)
- 2 : Valve lift adjustment valve
Tightening torque: 10 Nm (7.5 ft. lbs.)
13. Install ignition coils. Insert three ignition coils in the spark-plug recesses, position and then tighten two M6 x 25 hexagon socket head bolts.
Tightening torque: 10 Nm (7.5 ft. lbs.)
14. Install holder for the main muffler. Insert holder from the clutch side, position two M8 x 30 hexagon-head bolts at the top and two M8 x 25 hexagon-head bolts at the bottom and tighten. Connect the electrical plug of ignition coil cylinder 2 and the two electrical plugs of the magnetic hydraulic valves, then fasten the cable in the sheetmetal brackets.
Tightening torque: 23 Nm (17 ft. lbs.)
15. Install the shield. Insert the shield, position and tighten the two M6 x 16 hexagon-head bolts.
Tightening torque: 10 Nm (7.5 ft. lbs.)
16. Turn the engine at the assembly support by approximately 90° until the engine is horizontal (intake system at the top).
Tightening torques for installing camshaft