Installing Pistons

Information 

• Connecting rod bolts and bearing shells must always be replaced. 
• Turn the crankshaft so that the crank pin of the pistons to be removed is positioned outwards. 

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. 

Information 

Check allocation of piston rings.

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Allocation of piston rings

1. Compression ring with chamfer -arrow A-  at the inner top side.
2. Compression ring with shoulder -arrow B-  at the outer bottom side.
3. Oil scraper ring in three parts

1. Install compression rings.
   1. 1.1 Open compression ring -2-  using the piston ring pliers -3-  only as far as required so that it can be pushed over the piston -1-  .

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   Compression rings

2. Install oil scraper ring.
   1. 2.1 Check installation position of spring -1-  .
   2. 2.2 The gaps of the vanes -2, 3 -  and the spring -1-  must be offset by at least 90°.

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   Oil scraper ring

   Information 

   Check installation position of pistons:

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   Installation position of pistons

   • The arrow on both cylinder banks must face the direction of travel. 
   • The small valve recesses must face inwards to the inner V. 
   • x = Cylinder bank marking: L = left, R = right 
3. Insert piston -1-  .
   1. 3.1 Oil the cylinder liner, piston and piston rings with a small amount of engine oil.
   2. 3.2 Move piston ring gaps by 120°.
   3. 3.3 Align the crankshaft so that the corresponding crank pin is pointing straight down.
   4. 3.4 Carefully insert piston -1-  into the cylinder bore using > T90004 - funnel-2-  (-arrow-  ).
      1. 3.4.1 Use the handle of a hammer if necessary.
      2. 3.4.2 Check installation position of piston.
   5. 3.5 Push the piston downwards until the connecting rod bearing is sitting on the crank pin.

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   Piston with piston installation sleeve (similar to illustration)

   Information 

   When replacing connecting rods, please note the following:

   • Only one weight class can be installed per engine. 
   • The weight class is shown on the connecting rod cap. 
4. Install connecting-rod bearing cap -1-  according to the marking.
   1. 4.1 Oil connecting-rod bearing shells and crank pins.
   2. 4.2 The cast lugs on the ground surfaces of the connecting-rod pairs must be facing each another.
   3. 4.3 Fit connecting-rod bearing cap -1-  .
   4. 4.4 Fit and tighten screws -2-  .
   5. 4.5 Turn the crankshaft.
      1. 4.5.1 Check clearance of piston and oil spray jets.

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   Connecting-rod bearing cap

5. 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). Check for stiffness and irregularities while doing so. 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) or the connecting rod caps and connecting-rod big end all match.