Overhaul
WM 131037 Disassembling and assembling pistons on V6 DFI engines
Tools
Technical values
Preliminary work
1. Remove piston. -> 131019 Removing and installing pistons on V6 DFI engines Removal and Replacement
Tools and materials
Tools
Overview of special tools
Disassembling pistons
WARNING
Danger of injury due to piston pin circlip jumping off.
-> Make sure that the piston pin circlip is secured against jumping off at all times (wear gloves and hold circlip in position with thumb).
Information
- Combustion deposits on the piston crown are not to be removed mechanically.
Overview of piston/connecting rod
1. Insert piston in retaining device 9597.
Retaining device 9597
1.1. Adjust the length of the retaining device (Refer to Tools and Equipment).
1.2. Insert piston and connecting rod.
1.3. Fix the length of the retaining device.
Information
- When disassembling the piston/connecting rod unit, note or mark the position, relationship to cylinder and installation position using a waterproof felt tip pen.
- Some Figures show the piston of the V8 as the work steps are analagous.
2. Disconnect piston from the connecting rod.
Removing piston-pin circlips
2.1. Remove piston-pin circlip using a small screwdriver.
2.1.1. Guide the screwdriver through the small cut-out.
2.2. Repeat the process for the second piston-pin circlip.
Information
- If piston is sluggish, heat to 60 °C and remove and install with mandrel.
2.3. Then slide out the piston pin using a suitable mandrel.
Removing piston pin using mandrel
2.4. Pull connecting rod out of the piston and lay it side.
3. Remove piston rings using the piston ring pliers Gr. 1 NR.58.
CAUTION
Over-extension of piston rings due to incorrect assembly.
- Damage to piston rings.
-> Force apart the piston rings using the piston ring pliers just far enough for it to be possible to remove or install them.
3.1. Place the piston on a clean surface.
3.2. Remove the piston rings, starting from the piston crown.
3.3. To do this, place the middle point of the piston ring pliers at the gap in the piston ring.
3.4. The holding arms of the piston ring pliers should clasp the piston ring from above.
Information
- Compression rings and oil scraper rings are installed and removed differently.
Only open the piston ring as much as is needed to remove the piston ring from the groove.
Piston ring pliers No. 58
3.5. Relieve the piston ring pliers and remove the piston ring from the pliers.
4. Remove the oil scraper rings (three parts).
4.1. Remove the top oil scraper ring.
4.2. Remove the bottom oil scraper ring.
4.3. Then carefully remove the spring.
Assembling pistons
Information
- The connecting-rod bolts must be replaced.
1. Fit the oil scraper ring.
1.1. Carefully open up the oil scraper ring with your hand and insert it into the groove.
1.2. Fit the second ring over the oil scraper spring in the same way.
1.3. The gap in the oil scraper ring must be offset by exactly 180° with respect to the gap in the oil scraper spring when fitted. Make sure that the oil scraper spring is centred in the oil scraper ring.
CAUTION
Over-extension of piston rings due to incorrect assembly.
- Damage to piston rings.
-> Force apart the piston rings using the piston ring pliers just far enough for it to be possible to remove or install them.
2. Fit piston rings.
Piston ring inscription
Information
- The TOP marking must always face the piston crown.
2.1. Observe the Top marking.
2.2. Insert piston ring into the piston ring pliers.
2.3. First fit the bottom piston ring.
2.4. Then insert the top piston ring into the groove.
2.5. The gaps in the individual piston rings must always be offset by 120°.
3. Fit the piston pin.
3.1. Insert piston in retaining device 9597.
Information
- If piston is sluggish, heat to 60 °C and remove and install with mandrel.
3.2. Press the piston-pin circlip into the ring groove with your thumbs.
Inserting piston-pin circlip
Information
- The gap of the piston ring may not be located next to the removal recess.
3.3. Offset the ring gap in the piston-pin circlips by 30° with respect to the cut-out.
3.4. Insert piston-pin circlip.
Fitting piston-pin circlip
Lever the piston-pin circlip into the ring groove using a small screwdriver.
Levering in piston-pin circlip with a screwdriver
3.5. Place piston pin and connecting rod in installation position.
Retaining device 9597
3.6. The cast lugs on the connecting rod and connecting rod big end -1- must be on the narrow side of the piston -2-.
Marking on cast lugs on connecting rod and connecting rod big end
Information
- If piston is sluggish, heat to 60 °C and remove and install with mandrel.
3.7. Insert the oiled piston pin through the piston and connecting-rod eye as far as the circlip using a plastic hammer and pressure piece.
Pressure piece for piston pin
4. Fit the second piston-pin circlip in the same way.
Subsequent work
1. Install piston. -> 131019 Removing and installing pistons on V6 DFI engines Removal and Replacement
Overview of piston/connecting rod
