Checking Piston Wear

Information 

The pistons in the M97.70 and M97.70S engine are only available in one dimensional group and two weight groups.

→ Avoid contact with caustic fluid.

→ Wear personal protective gear.

→ Ensure that there is good ventilation.

→ If you do come into contact, wash off immediately with plenty of warm water and contact a doctor if necessary.

1. Clean removed pistons with solvent naphtha.
2. Check the piston diameter -D-  at the prescribed measuring point on the piston shank using an outside micrometer.

   Measuring point from lower edge of shank X = 15 mm  .

   Fig 1: Checking Piston Shank Diameter

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Information 

• If the wear limit is exceeded, the piston and cylinder sleeve must be replaced. 

The maximum wear allowed at the specified measuring point is 100 μm (= 0.1 mm). If this measurement is exceeded, the piston must be replaced. The reference measurements are listed in the table below.