Pistons and conrods – assembly overview and fastening

• 1 Retaining ring
• 2 Piston pin
  • If difficult to remove, heat piston to 60°C.
  • Remove and install using drift - 10 - 14-.
• 3 Piston
  • Checking ⇒ 4.2 Checking piston
  • Mark installation position and cylinder number.

• 4 Compression rings
  • Offset gaps by 120°
  • Remove and install compression rings with piston ring pliers.
  • “TOP” faces towards piston crown.
  • Checking ring gap ⇒ 4.2 Checking piston.
  • Checking ring-to-groove clearance ⇒ 4.2 Checking piston.
• 5 Oil scraper rings
  • Carefully remove and install 3-part oil scraper rings by hand.
  • Checking ring gap ⇒ 4.2 Checking piston.
  • Ring-to-groove clearance not measurable.

• 6 Conrod bolt
  • M7×0.75: 20 Nm + ¹/4 turn (90°) further.
  • M8×1: 30 Nm + ¹/4 turn (90°) further.
  • Renew
  • Oil threads and contact surface
  • To measure radial clearance, tighten to corresponding specified torque but not further.
• 7 Conrod bearing cap
  • The caps only fit in one position and only on the appropriate conrod due to the breaking procedure (cracking) separating the cap from the conrod.
  • Markings -A-: mark with cylinder number
  • Markings -B-: mark paired conrods and conrod bearing caps
• 8 Bearing shell
  • Do not interchange used bearing shells.
  • Insert bearing shells centrally.

Checking radial clearance with Plastigage:

• New: 0.020…0.060 mm
• Wear limit: 0.090 mm
• Do not rotate crankshaft when checking radial clearance.

• 9 27 Nm
  • Opening pressure of pressure relief valve: 1.8…2.2 bar
• 10 Oil spray jet
  • For piston cooling.
• 11 Connecting rod
  • Renew as set only.
  • Markings -A-: mark with cylinder number
  • Markings -B-: mark paired conrods and conrod bearing caps
  • Separating new conrod ⇒ 4.4 Separating new conrod.

If new conrods are fitted, then the choice of position is arbitrary.

• Guided axially by piston.