Part 2
WM 1001Z2 Assembling V8 4.8-litre DFI engine as of October 2008
Connecting-rod assembly, bearing shells
Piston classification
7.1. Select the pistons based on cylinder bank and pre-fit a piston-pin circlip. One end of the piston-pin circlip is inserted into the ring groove of the piston pin eye -1-. Press the other end into the ring groove with your thumb. -finger- The opening of the piston-pin circlip is pointing to 6 or 11 o'clock.
Piston-pin circlip
7.2. Lever the piston-pin circlip into the ring groove using a small screwdriver while continuing to press it down. => see figure
Inserting piston-pin circlip
7.3. If the piston-pin circlip does not slide into the ring groove right away, press the other end of the piston-pin circlip into the ring groove -arrow-. Check that the circlip is seated correctly.
Pressing piston-pin circlip into ring groove
Information
- The corresponding connecting-rod bearing shells must be selected according to the marking on the crankshaft transmission flange (4-digit) and inserted into the connecting rod.
- When removing the pistons with connecting rods, the pistons should be marked with a water-resistant marker on both the piston and connecting rod according to cylinder and cylinder bank.
- The removed pistons and connecting rods must be cleaned carefully so as not to remove the markings.
- The connecting rod code is installed to the exhaust side as standard. The direction of travel arrow on the DFI piston is always on the same side as the connecting rod code -A-. The pistons are assigned to the cylinder bank (1 to 4 and 5 to 8), i.e. because of the DFI combustion chamber recess there are two different pistons for the left and right cylinder bank.
- When installing the piston in the crankcase, the direction of travel arrow must point in the direction of travel when installed. It is always on the same side as the connecting rod code. The combustion chamber recess on the piston is always on the intake side. Note the assignment of the pistons to the cylinder bank.
- Naturally aspirated engines and turbo engines have different pistons.
Connecting rod code and direction of travel arrow
- The code on the connecting-rod big end and connecting rod cap must always be on the same side and at the exhaust side. -A- Note: Select the correct piston for the correct cylinder bank. Install with connecting rod code on the exhaust side with the direction of travel arrow on the piston.
Connecting rod code "A"
7.4. Turn piston and move connecting rod to the correct installation position. Insert connecting rod into piston.
Piston on retaining device
7.5. Oil piston pin and all contact points.
7.6. Fit piston pin using plunger 9500/8 and fit second piston-pin circlip. Check for smooth operation.
Piston pin with plunger
7.7. Place piston, with the connecting rod fitted, on a soft surface. Do not use the vice to secure the connecting rod.
7.8. When fitting piston rings, the oil scraper ring is fitted first.
7.9. Carefully insert inner spring into the lower groove by hand, keeping it away from the piston crown.
7.10. Insert oil scraper ring over the inner spring into the groove by hand. "TOP" marking on piston rings must always be facing upwards to the piston crown. Spread piston rings just far enough for them to fit over the piston. Avoid straining the piston rings as this will result in permanent deformation of the piston ring.
7.11. Select both compression rings based on the height of the corresponding piston ring groove and install with the "TOP" marking facing the piston crown.
7.12. Clamp the piston ring gap using piston ring pliers or by hand and insert into the appropriate piston ring groove.
Piston ring pliers on piston ring
7.13. Twist piston ring gaps so that they are offset with respect to each other by 120°.
7.14. Oil piston rings and set down the assembly-ready piston. Fit remaining pistons and connecting rods in the same way.
Information
- The corresponding connecting-rod bearing shells must be selected according to the marking on the crankshaft transmission flange (4-digit) and inserted into the connecting rod.
- When removing the pistons with connecting rods, the pistons should be marked with a water-resistant marker on both the piston and connecting rod according to cylinder and cylinder bank.
- The removed pistons and connecting rods must be cleaned carefully so as not to remove the markings.
- The connecting rod code is installed to the exhaust side as standard. The direction of travel arrow on the DFI piston is always on the same side as the connecting rod code -A-. The pistons are assigned to the cylinder bank (1 to 4 and 5 to 8), i.e. because of the DFI combustion chamber recess there are two different pistons for the left and right cylinder bank.
- When installing the piston in the crankcase, the direction of travel arrow must point in the direction of travel when installed. It is always on the same side as the connecting rod code. The combustion chamber recess on the piston is always on the intake side. Note the assignment of the pistons to the cylinder bank.
- Naturally aspirated engines and turbo engines have different pistons.
Connecting rod code and direction of travel arrow
- The code on the connecting-rod big end and connecting rod cap must always be on the same side and at the exhaust side. -A- Note: Select the correct piston for the correct cylinder bank. Install with connecting rod code on the exhaust side with the direction of travel arrow on the piston.
Connecting rod code "A"
7.15. Select connecting-rod bearing shells based on the marking on the crankshaft flywheel flange and insert into the connecting-rod big end and the connecting rod cap according to the twist lock. Fit connecting rod bearing cap onto the connecting-rod big end again hand-tight.
7.16. Place all eight pistons with the connecting rods fitted on a clean surface, sorted by cylinder.
8. Grease seal on thermostat insert sparingly with Kluber Syntheso GLEP 1 and fit it into the thermostat housing by hand. Press thermostat insert in as far as it will go. For details, see -> 195819 Removing and installing coolant regulator (thermostat) on DFI engines - section on "Installing" Service and Repair
9. Check that all the seals are installed in the oil plate.
Oil guide (oil plate)
10. If you have not already done so, drive eight dowel sleeves for the metal seals in the timing-case cover using a copper or plastic hammer. Insert metal seals and press on dowel sleeves. Set down timing-case cover.
11. Oil pump is pre-fitted with the oil pressure control valve.
12. Cylinder heads fitted with solenoid valves of the valve lift switchover, camshaft housings loosely positioned and removed camshafts prepared. Alternatively, the camshaft housings, which have been marked according to installation position, can be set down on a clean surface together with the corresponding camshafts. Cam followers and injectors are fitted.
13. If you have not already done so, drive in dowel sleeves on auxiliary unit bracket for power-steering pump or tandem pump using a copper or plastic hammer.
14. Move starter into installation position and screw down. => Tightening torque: 45 Nm (33 ftlb.)+8 Nm (+6 ftlb.)
15. Insert oil spray jets into upper part of crankcase and screw down => Tightening torque: 10 Nm (7.5 ftlb.). To do this, grease the sealing ring sparingly with Kluber Syntheso GLEP 1 and fit it. Check that oil spray jets are pointing in the correct direction of spray toward the inside of the piston crown. The oil spray jet must be aimed at the piston crown. => Spray direction => Spray direction from side
Spray direction
Spray direction from side
16. Insert crankshaft and oil crankshaft bearing pin and connecting-rod bearing pin.
17. First position timing chain pinion with the ring gear of the oil pump drive onto the crankshaft stub (check that the two diamond washers at the front and rear on the ring gear are clipped in -1- ). Then position the drive pinion of the oil pump chain -2- with respect to the crankcase.
Timing chain pinion on crankshaft stub
Timing chain pinion with two diamond washers
18. Fit crankshaft holding bridge holding bridge 9677/1 in the centre of the crankshaft.
Crankshaft secured
19. Turn upper part of crankcase and oil cylinder liners.
20. Tension piston using a commercially available piston ring restraining strap (e.g. Universal piston ring restraining strap Nr.55 ) or assembly funnel funnel 9784/1 and press piston into cylinder. When doing so, make sure that the direction of travel arrow on the piston crown is pointing in the direction of travel and the connecting rod code has been fitted facing the exhaust side. Push the pistons in until the connecting rod bearing is lying on the con-rod journal of the crankshaft. Once all the pistons with connecting rod have been pushed in, fit connecting rod cap evenly and synchronously with the correct bearing shell. Fit with new connecting rod bolt to the prescribed tightening torque. For details, see -> 131020 Removing and installing pistons on 4.8-litre DFI engines 131020 Removing and installing pistons on 4.8-litre DFI engines
Piston, connecting rod
Tensioning pistons
Piston assembly
Pressing in pistons
21. Remove crankshaft holding bridge. Apply Doboseal 224N sealant (999.915.573.43, status 09/08) to the lower part of the crankcase. Insert sealing ring -3- into the upper part of the crankcase and position the lower part of the crankcase onto the upper part of the crankcase. Insert all the fastening screws, fit to the prescribed tightening torque within 5 minutes and wipe off excess sealant.
Applying sealant
22. Tighten M11 and M10 bearing screws to the prescribed torques. -5 and 6-
Tightening sequence for thrust-bearing screws
Lower part of crankcase
23. Fit cross bolt connection.
Tightening sequence for securing lower part of crankcase to upper part of crankcase (cross bolt connection)
24. Fit M8 screws on the side -8 and 9-. Remove emerging sealant.
25. Punch in or imprint the engine number if necessary (when replacing engine).
26. Move oil plate with all the seals into installation position and secure to the lower part of the crankcase. => Tightening torque: 10 Nm (7.5 ftlb.)
Oil guide (oil plate)
27. Grease sealing ring between the oil plate transfer pipe and oil pump sparingly with Kluber Syntheso GLEP 1 and fit oil pump. Secure the oil pump.
Oil pump on turbo engine M48/51 with oil extraction stage
28. Fit oil pump sprocket with drive chain with respect to the crankshaft chain pinion => Oil pump chain. Counter the oil pump sprocket at the oil pump using a screwdriver and fit a new screw. 1st turn => Initial tightening: 20 Nm (15 ftlb.) ; final tightening (torque angle) => Torque angle: 90°
Oil pump chain
Countering oil pump pinion
29. Fit cover plate for oil pump drive using three screws. => Tightening torque: 10 Nm (7.5 ftlb.)
30. Turn engine and clean sealing faces. Blow out bores of cylinder head screws. Position both cylinder head seals. Part number/marking facing upward. When doing so, make sure that the cylinder head gasket is positioned on the dowel sleeves.
31. Unscrew front camshaft mounting saddles (lower parts) of the cylinder heads (if you have not already done so), as the bores in the cylinder head screws are covered. see illustration, item 8
Camshafts, cylinder bank 1 to 4
32. Position cylinder heads, insert cylinder head screws and fit them. Observe tightening sequence and prescribed tightening torque.
Cylinder head 1 to 4
Tightening sequence for cylinder head
