Part 2
WM 131020 Removing and installing pistons and handling toolsAssembly
Pre-fitting pistons and connecting rods
Information
- Ensure even weight distribution when installing new pistons or connecting rods.
- Only one weight group is permitted per engine.
Component overview
Connecting rod bolts
Tools:
Tool 9778
Information
- The parting surface between the connecting rod and connecting rod cap is broken during the manufacturing process.
- Assign connecting rod cap to the relevant connecting rod immediately after removal.
- Also check the four-digit matching number.
- Replace connecting rod bolts.
- Replace connecting rod bearings.
1. Allocate connecting rod bearings based on the marking on the crankshaft.
1.1. Read off the bearing shell colour from the series of letters -2-. The con-rod marking indicates the con-rod journal. This is read from left to right. The bearings are fitted from the belt side to the flywheel side.
Marking for bearing shell allocation on the crankshaft
1.2. Fit new con-rod bearing shells in the connecting rod cap and connecting rod and grease with Optimol Optipit grease (Part No. 000.043.204.17).
1.3. Check that the new con-rod bearing shells are seated correctly (check locking lugs) -arrow-.
Locking lugs for connecting rod bearings
1.4. Secure connecting rod cap with relevant connecting rod and new M10 x 1.25 x 51 screws by hand.
2. Fit pistons and connecting rods for cylinders 4-6 (the positions of the above-mentioned markings also apply for the pistons and connecting rods for cylinders 1-3).
2.1. The matching number -2- and data matrix code -inset- on the correctly installed connecting rod must be facing the exhaust side.
Matching number on connecting rod
2.2. In contrast, the cone-shaped neck and data matrix code -1- on the piston must be facing the intake side.
2.3. The pistons for cylinders 1-3 are pre-fitted without connecting rods.
3. Insert piston and connecting rod -1- or only the piston into the retaining device 9778 (3.6 and 3.4-litre) -2-.
3.1. In the case of 2.9-litre pistons, pull off piston receiving element 9778 and then attach piston receiving element 9778/2.
Piston/connecting rod in retaining device 9778
WARNING
Preloaded or pressurised components
- Risk of eye injuries
- Risk of bruising
-> Wear personal protective gear.
-> Secure components to prevent them from falling off suddenly.
4. First, fit the piston-pin circlip, which must be facing the flywheel side later.
4.1. Fit the circlip on the side of the piston that does not have an assembly groove for the assembly tool 9776.
4.2. Fit the circlip -1- at the position shown. A small screwdriver can be used to do this.
4.3. Press the circlip in with your thumbs and guide it to its final position with the screwdriver.
Circlip facing flywheel side - hook at 12 o'clock position (engine in vertical position)
Pistons and connecting rods for cylinders 4-6:
5. Turn piston and connecting rod by 180° and fit the circlip, which must be facing the belt side later. Use special tool assembly tool 9776 to do this.
5.1. Coat piston pin with new engine oil and press it into the relevant piston/connecting rod assembly.
5.2. Turn the groove for the small hook on the tool -1- towards the observer.
Pressing piston-pin circlip into tool 9776
5.3. Slide a new circlip -2- into the assembly tool and press the edges together.
5.4. Position the small hook towards the groove -arrow-. Turn the circlip slightly if necessary.
Small hook facing groove
Turn the circlip -2- by hand as required:
Turning piston-pin circlip in tool
5.5. Pull back and hold push bar in tool. Place the pipe -1- on a hard surface. Slowly guide the push bar down and press the circlip into installation position. You should hear a distinct click.
Pressing circlip into installation position
6. Assembly tool 9776 must be positioned on the piston in such a way that the small hook is lying in the half-moon-shaped bore -arrow-.
Tool 9776 at assembly groove on piston
The piston would see the ring -1- in the position shown in the tool -2-.
Circlip position viewed from the piston (towards belt side)
6.1. Hold on firmly to the tube of the tool -1- and tap the push bar slightly towards the piston with the ball of your hand -arrow-. The circlip will lock with a clearly audible click.
Fitting circlip on piston in retaining device 9778
6.2. The circlip -1- must be fitted as shown. The hook -2- is at the 9 o'clock position.
Circlip fitted (viewed from belt side)
7. Remove piston and connecting rod from the retaining device 9778.
Installing pistons
Installing pistons - cylinder bank 4-6
Preliminary work: Crankshaft is inserted in crankcase half 4-6; pistons and connecting rods are pre-fitted (see Assembly).
1. Secure the crankshaft to the main bearing in the middle using holding bridge 9779 -1-.
1.1. Tighten two fastening screws -2- hand-tight.
Holding bridge 9779 for crankshaft
2. Tighten three external Torx screws (M8 x 1 x 25) -2- used to secure the vibration damper to the crankshaft flange hand-tight.
2.1. Turn the crankshaft using turning device 9773 -1- so that the con-rod journal is at bottom dead centre position.
Turning the crankshaft (without vibration damper)
Information
- The parting surface between the connecting rod and connecting rod cap is broken during the manufacturing process.
- Assign connecting rod cap to the relevant connecting rod immediately after removal.
- Also check the four-digit matching number.
- Replace connecting rod bolts.
- Replace connecting rod bearings.
3. Check that the new con-rod bearing shells are seated correctly (check locking lugs).
Locking lugs for connecting rod bearings
3.1. Check allocation of connecting rod to connecting rod cap (matching number -1- and data matrix code). These must be facing the exhaust manifold in installation position.
Connecting rod on crankshaft
4. Install piston and connecting rod.
4.1. For re-installation, fit the relevant piston into the related cylinder bore according to the inscription -4 to 6- (cylinder 4 on belt side).
Marking and installation position of pistons 4-6
4.2. Check installation position of pistons. The cone-shaped neck -1- must be facing the intake side -E-. The matching number and data matrix code on the connecting rod -2- must be facing the exhaust side.
Matching number on connecting rod
4.3. Align piston rings. Offset the ring gaps by 120°. Check the twist lock -arrow- at the second ring groove.
Twist lock on second piston ring
4.4. Coat piston and tools funnel 9784 (3.4-litre) or funnel 9784/3 (2.9-litre) with new engine oil.
4.5. Slide the piston -1- as far as required into the assembly funnel -2- until the lower edge of the piston is flush with the surface of the tool.
Lower edge of piston flush with surface of assembly funnel
4.6. Guide connecting rod and piston -1- into the cylinder bore and place assembly funnel -2- on the crankcase.
Inserting piston into cylinder bore
4.7. Press the piston into the cylinder bore immediately and hold the assembly funnel -1- firmly while doing this. The wooden or plastic handle of a hammer -2- can be used to do this.
Pressing in piston
4.8. Remove assembly funnel.
4.9. Fit the correct connecting rod cap with new screws.
4.10. Repeat these steps for pistons 5 and 6.
5. Pre-fit connecting rods 1-3 with new bearings and the relevant connecting rod caps and new screws -2- on the crankshaft.
Connecting rod cap on cylinder bank 1-3
5.1. The matching number -1- and data matrix code are facing the exhaust side.
Connecting rod on crankshaft
6. Tighten all connecting rod caps -2- according to specifications.
Connecting rod cap screws
=> Initial tightening: 20 Nm (15 ftlb.)
=> Final tightening - torque angle: 80°
7. Fit rubber sleeves on connecting rods 1-3 to protect the cylinder lining ( assembly aid 9795 ).
Installing pistons - cylinder bank 1-3
WARNING
Preloaded or pressurised components
- Risk of eye injuries
- Risk of bruising
-> Wear personal protective gear.
-> Secure components to prevent them from falling off suddenly.
1. Assemble the crankcase.
-> 1001Z2 Assembling engine 1001Z2 Assembling engine.
2. Secure the vibration damper to the crankshaft flange with two external Torx screws (M8 x 1 x 25).
3. Turn con-rod journal for cylinder 3 to installation position.
3.1. To do this, use turning device 9773 to turn the crankshaft to the bottom dead centre position U 3/6 at the vibration damper.
Position U 3/6
4. Pull off the boot on the connecting rod -1- , set it in a vertical position and secure in place with a centring mandrel 9782 (diameter: 22 mm) -2-.
Guiding centring mandrel into assembly bore
View through cylinder bore: connecting rod eye -1- and centring mandrel -2-.
centering the connecting rod using tool 9782 (diameter: 22 mm)
5. Install pistons for cylinders 1-3.
5.1. Insert displacement bodies -1-.
5.2. For re-installation, fit the relevant piston into the related cylinder bore according to the inscription -1 to 3- (cylinder 3 on flywheel side).
Marking pistons
5.3. Check installation position of pistons. The cone-shaped neck and data matrix code on the piston -1- must be facing the intake side, while the matching number -2- and data matrix code on the connecting rod must be facing the exhaust side.
Matching number on connecting rod
5.4. Align piston rings. Offset the ring gaps by 120°. Check the twist lock -arrow- at the second ring groove.
Twist lock on second piston ring
5.5. Coat piston and tools funnel 9784 (3.4-litre) or funnel 9784/3 (2.9-litre) with new engine oil.
5.6. Insert the piston into the assembly sleeve -1- until the lower edge of the piston is flush with the surface of the sleeve -arrow-.
Inserting piston into assembly sleeve
5.7. Guide the piston -1- into the cylinder bore and carefully position the funnel -2- on the crankcase.
Inserting piston into cylinder bore
5.8. Press the piston into the cylinder bore immediately and hold the assembly funnel -1- firmly while doing this. The wooden handle of a hammer -2- can be used to do this.
Pressing in piston
5.9. Remove assembly funnel.
6. Position piston in order to fit piston pin and circlip.
6.1. Tools for 3.4-litre pistons: Piston assembly aid 9787 with spacer ring 9787/3 and handle of assembly aid 9598.
6.2. Tools for 2.9-litre pistons: Piston assembly aid 9787/2 and handle of assembly aid 9598.
6.3. Use the relevant tool -1- to press the piston into the cylinder bore as far as the contact surface of the centring mandrel 9782 -2-.
Pressing in piston using assembly aid 9787
6.4. Pull out the centring mandrel -2- and press the piston down at the same time until the assembly aid -1- is positioned correctly.
7. Fix piston and connecting rod in place using a centring mandrel 9782.
centering piston and connecting rod
8. Fit the piston pin.
8.1. Coat the piston pin with new engine oil and slide it onto the disassembly tool 9777.
8.2. Secure the tool at the front hexagon -1- and turn it anti-clockwise as far as it will go at the rear hexagon -2-.
Sliding tool 9777 into piston pin
8.3. Slide the piston pin -1- into the piston/connecting rod eye. Use the tool -2- to guide the pin past the edge of the cylinder to the piston -arrow-.
Fitting piston pin
8.4. Tap the tool lightly with the ball of your hand, if necessary, while holding the tool firmly in place -1-. Insert pin as far as it will go (touching the circlip).
Tapping in piston pin using tool
8.5. Turn the tool at the rear hexagon -2- in clockwise direction until it pulls easily out of the piston pin without resistance.
Loosening tool 9777 on piston pin
Information
- Always replace piston-pin circlips following removal.
9. Insert new piston-pin circlip into assembly tool 9776.
9.1. The large hook -1- on the circlip will have to be at 9 o'clock position later (when engine is vertical).
Large circlip hook at 9 o'clock position
9.2. Turn the groove for the small hook on the tool -1- towards the observer.
Pressing piston-pin circlip into tool 9776
9.3. Slide a new circlip -2- into the assembly tool and press the edges together.
9.4. Position small hook facing the groove -arrow-.
Small hook facing groove
Turn the circlip -2- as required:
Turning piston-pin circlip in tool
9.5. Pull back and hold push bar in tool. Place the pipe -1- on a hard surface. Slowly guide the push bar down and press the circlip into installation position. You should hear a distinct click.
Pressing circlip into installation position
10. Fit the piston-pin circlip on the piston.
10.1. Assembly tool 9776 -1- must now be guided into the assembly bore.
Guiding tool 9776 into assembly bore
View of circlip in tool 9776 in front of assembly bore
10.2. Position the tool with the small hook -arrow- at about 11 o'clock position and place it in the assembly groove on the piston.
Small hook at 11 o'clock position
10.3. Carefully turn the tube of the tool to the left and right while pressing slightly against the piston at the same time. You should feel a certain amount of resistance in the half-moon-shaped bore on the piston at both sides.
Turning tool 9776
10.4. Press the tube of the tool against the piston and hold it firmly in place. Then, tap the push bar slightly towards the piston with the ball of your hand. The circlip will lock with a clearly audible click.
10.5. Assembly tool 9776 must now be removed.
10.6. Check that the piston-pin circlip is seated correctly over cylinder bore 2 using a mirror -1- and a torch. The correct assembly position is clearly visible -2-.
Checking position of piston-pin circlip using a mirror
11. Turn con-rod journal for cylinder 2 to installation position.
11.1. To do this, use turning device 9773 to turn the crankshaft to the bottom dead centre position U 2/5 at the vibration damper.
Position U 2/5
11.2. Repeat steps 3-10 for cylinder 2. Check the position of the circlip over cylinder bore 1.
12. Turn con-rod journal for cylinder 1 to installation position.
12.1. To do this, use turning device 9773 to turn the crankshaft to the bottom dead centre position U 1/4 at the vibration damper.
Position U 1/4
12.2. Repeat steps 3-10 for cylinder 1.
12.3. The position of the circlip can be checked on cylinder 1 through the assembly bore. The large hook -1- must be at 9 o'clock position when the engine is vertical.
Installation position of circlip in piston
13. Fit screw plug (M30 x 1.5) -1- for fitting piston pin with a new sealing ring.
Screw plug for removing/fitting piston pins
13.1. => Tightening torque: 80 Nm (59 ftlb.)
14. Complete the engine.
-> 1001Z2 Assembling engine 1001Z2 Assembling engine.