131020 Removing and installing pistons on 4.8-litre DFI engines
WM 131020 Removing and installing pistons on 4.8-litre DFI engines
Tools
Technical values
Preliminary work
1. Remove the engine. -> 100119 Removing and installing V8 4.8-litre DFI engine - section on "Removing" 100119 Removing and installing V8 4.8-litre DFI engine
2. Remove engine from transmission. -> 100127 Removing engine from transmission and mounting engine on transmission - section on "Removing" 100127 Removing engine from transmission and mounting engine on transmission
3. Secure engine on assembly support. -> 1001IN Securing V8 4.8-litre DFI engine on mounting bracket 1001IN Securing V8 4.8l DFI engine on the mounting bracket
4. Drain engine oil. For details, see -> 170117 Changing engine oil and oil filter on DFI engines - section on "Draining and filling" Service and Repair
5. Remove timing chain. -> 153519 Removing and installing timing chain on 4.8-litre DFI engines - section on "Removing" Removal and Replacement
6. Remove cylinder heads. -> 157019 Removing and installing cylinder head on 4.8-litre DFI engines - section on "Removing" 157019 Removing and installing cylinder head on 4.8-litre DFI engines
7. Remove oil pan and oil guide housing. -> 175019 Removing and installing oil pan and oil guide housing on 4.8-litre DFI engines - section on "Removing" Removal and Replacement
8. Remove oil pump. -> 172019 Removing and installing oil pump on 4.8-litre DFI engines - section on "Removing" Service and Repair
Information
Component overview
Piston, connecting rod
Connecting-rod assembly, bearing shells
Piston classification
Crankshaft
Identification of pistons
Information
The piston is identified as a spare part by the following characteristics: one dimensional group X , Naturally aspirated or Turbo , cylinder bank 1 to 4 or 5 to 8.
The piston is installed as standard in two additional weight tolerances: + and -.
This information is all engraved on the piston crown. To identify the piston uniquely, the piston must be cleaned carefully (brass brush, ultrasound bath).
Markings on piston crown: Replacement pistons are only available from the Porsche Parts Service in dimensional group 'X' and in two weight tolerances '+' and '-'.
Piston classification
1. In the event of repairs, the removed piston must be cleaned and identified. If the piston needs to be replaced, an X piston with the identified weight tolerance + or - for the correct cylinder bank is ordered and installed as a spare part.
Removing pistons
Information
- Note the association between the connecting-rod big end and the connecting-rod bearing cap as the cracked connecting rods only fit in one position.
- The retaining lugs of the connecting-rod bearing shells are always located on the same side in order to prevent the bearing shells from turning.
- The connecting-rod bearing cap and the big end of the connecting-rod bearing have the same connecting-rod numbers.
1. Remove oil return (oil plate) under the oil pump.
Oil guide (oil plate)
2. Loosen connecting rod bolts -6- and take off connecting rod caps -5-. Push piston in question out of the crankcase using a wooden rod. Hold it in your other hand or get another person to help. Fit connecting rod cap hand-tight to the connecting rod again using the old screws and set down after marking according to the relevant cylinder.
The connecting rods are cracked and the connecting rod code is facing the exhaust side.
The combustion chamber recess on the piston is facing the injector.
Piston, connecting rod
Information
- Connecting rod bolts and bearing shells must always be replaced.
- Turn the crankshaft so that the crank pin of the piston to be removed stands vertically upwards.
3. Remove the remaining pistons using the same procedure.
Installing pistons
Information
- Connecting rod bolts and bearing shells must always be replaced.
- The marking on the main bearings and connecting rod bearings is located on the flywheel flange of the crankshaft.
Information
- The pistons must already be pre-fitted (pistons, piston rings, connecting rods and fastening material) before performing the next step.
- Fit the number on the connecting rod -A- facing the exhaust side.
- When installing the piston in the crankcase, the direction of travel arrow on the piston crown must point in the direction of travel.
- The code on the connecting-rod big end and connecting rod cap must be on the same side -A-.
Surface with cylinder number marking
- The direction of travel arrow is on the same side as the connecting rod code -A- on the piston shown. Fit the number on the connecting rod -A- facing the exhaust side.
Allocation
- The direction of travel arrow must be pointing forwards (in direction of travel) when installed -inset-. The combustion chamber recess -1- on the DFI piston is facing the inner V (centre of the engine) when installed -top arrow-.
Installed DFI piston in crankcase
Installing pistons - direction of travel arrow
1. Turn the engine in the engine support so that the crankshaft lies at the bottom.
2. Install the piston. To do this, turn the crankshaft with a wrench (a/f 27) until the corresponding crank pin is pointing vertically downwards.
3. Lightly oil the cylinder, piston and funnel 9784/1 ( -1- ). Alternatively, a commercially available piston ring restraining strap piston ring restraining strap for 944 - S2 and Boxster and 911 Carrera (996) NR.57 can be used.
Oiling the piston funnel
4. Align piston-ring set (offset by 120°) and compress piston rings using piston ring restraining strap for 944 - S2 and Boxster and 911 Carrera (996) NR.57. Ensure that all piston rings are correctly tensioned by the special tool -see Figure-. If you are using a funnel 9784/1 , slide the piston with connecting rod fitted into the funnel -2-. The collar of the funnel must be facing the crankcase -1-. Slide the piston into the funnel until the piston shank protrudes approx. one centimetre down out of the funnel. => Piston inserted in piston funnel
Inserting piston into piston funnel
Piston inserted in piston funnel
Piston with restraining strap
5. Place the piston onto the cylinder from above and slide it into the cylinder using the handle of a hammer if necessary. When doing so, make sure that the direction of travel arrow is pointing forwards -see arrow (Figure shows cylinder 1)-. If you are using the funnel 9784/1 , position it flush on the crankcase -3-. Check the position of the combustion chamber recess -1- and the direction of travel arrow when doing this.
Installing pistons
Fitting piston
6. Push the piston down until the connecting rod bearing is sitting on the lift pin. Push it down further using the handle of a hammer if necessary -see Figure-. Do not use force. If the piston is jammed in the tool, oil the tool again if necessary or carefully loosen and turn the piston.
Pressing in piston
7. Oil connecting-rod bearing shells and crank pins.
Information
- The piston connecting rods are cracked and only fit in one position (in conjunction with the matching numbers).
- Install con-rod code towards exhaust side -A-.
Surface with cylinder number marking
8. Then fit the connecting rod cap with bearing shell (twist lock together) => Retaining lugs for connecting rod bearings -B and C-. The connecting rod numbers must be facing each other => View of matching numbers -A-. Fit connecting rod bolts by hand.
Retaining lugs for connecting rod bearings -B and C-
View of matching numbers -A-
9. Fit the opposite piston (cylinders 1 and 4).
10. Fit other pistons using the procedure described above.
11. Turn crankcase on the assembly support until the crankshaft is on top.
12. Tighten connecting rod bolts that have been replaced. Turn the crankshaft until the corresponding crank pin is pointing vertically upwards. Tighten bolts with a multiple-tooth nut.
13. Once all pistons have been correctly fitted and secured, turn the crankshaft in a clockwise direction to check it using a ring wrench (a/f 27). When doing so, watch out for stiffness and irregularities. If the crankshaft cannot be turned or if it is very stiff, check whether the installation direction (arrow) of the pistons, the pistons and the cylinders (markings) and the connecting rod caps and connecting-rod big end all match.
Subsequent work
1. Fit oil guide/oil plate.
Oil guide (oil plate)
2. Install oil pump. -> 172019 Removing and installing oil pump on 4.8-litre DFI engines - section on "Installing" Service and Repair
3. Install cylinder heads. -> 157019 Removing and installing cylinder head on 4.8-litre DFI engines - section on "Installing" 157019 Removing and installing cylinder head on 4.8-litre DFI engines
4. Fit timing chain. -> 153519 Removing and installing timing chain on 4.8-litre DFI engines - section on "Installing" Removal and Replacement
5. Fit timing-case cover. -> 153319 Removing and installing timing-case cover on 4.8-litre DFI engines - section on "Installing" Removal and Replacement
6. Fit oil pan and oil guide housing. -> 175019 Removing and installing oil pan and oil guide housing on 4.8-litre DFI engines - section on "Installing" Removal and Replacement
7. Fill in engine oil. For details, see -> 170117 Changing engine oil and oil filter on DFI engines Service and Repair
8. Remove engine from the assembly support.
9. Mount engine on transmission. -> 100127 Removing engine from transmission and mounting engine on transmission - section on "Mounting" 100127 Removing engine from transmission and mounting engine on transmission
10. Install the engine. -> 100119 Removing and installing V8 4.8-litre DFI engine - section on "Installing" 100119 Removing and installing V8 4.8-litre DFI engine