Audi A4 Workshop Service and Auto Repair Manuals

Pistons

→ Position: arrow on piston crown must always face in direction of travel.

• ‒ Mark cylinder number on piston crown with waterproof felt pen.

Note:

Do not use a centre-punch or similar, as pistons have a special coating.

Checking piston diameter

• ‒ → Measure pistons approx. 10 mm from bottom of skirt, at 90° to piston pin axis.
• ‒ Difference between actual and nominal diameter:
  not more than 0.04 mm.

→ Ring-to-groove clearance

→ Checking piston ring gap

• ‒ Push ring in squarely to a position approx. 15 mm from bottom end of cylinder.