Piston And Cylinder Bore, Checking

Pistons, Checking

Fig 1: Checking Piston Bore

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Measure approximately 10 mm in from the lower edge at a 90° angle to the piston pin axis using an external micrometer.

Maximum variance from the specified size: 0.04 mm.

Piston Diameter in mm
Specified size	74.42 ¹⁾
¹⁾ dimensions without coating Piston manufacturer: Federal Mogul (thickness: 0.018 mm on each side) Piston manufacturer: Mahle (thickness: 0.015 mm on each side)

Piston Ring Gap, Measuring

Fig 2: Checking Piston Ring Gap

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Push the piston ring squarely from above down to approximately 15 mm from the bottom end of the cylinder.

-- Use a piston without a piston ring for pushing it in.

Piston Ring	New mm	Wear Limit mm
Compression ring	0.20 ^{+ 0.15}	1.0
Oil scraping ring (2 parts)	0.20 ^{+ 0.20}	3.0
Oil scraping ring (3 parts)	0.50 ^+/-0.25	3.0

Piston Ring Height Clearance, Measuring

Fig 3: Checking Piston Ring Groove Clearance

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Clean the piston ring groove before checking.

Piston Ring	New mm	Wear Limit mm
1. Compression ring (piston ring manufacturer: Federal Mogul)	0.050 to 0.090	0.15
1. Compression ring (piston ring manufacturer: Mahle)	0.035 to 0.085	0.15
2. Compression ring	0.030 to 0.070	0.15
Oil scraping rings (three-part)	cannot be measured
Oil scraping rings (two-part)	0.04 to 0.08

Cylinder Bore, Measuring

Fig 4: Checking Cylinder Bore (Dimensions)

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

NOTE:

Risk of damaging the cylinder bore surface through incorrect handling.

Never handle the cylinder bore with service equipment (drilling, honing, Lapping).

-- Using the Cylinder Dial Bore Gauge: VAS6078 , measure in a diagonal sequence at three positions transversely -A- and longitudinally -B-.

Maximum variance from the specified size: 0.08 mm.

Cylinder Bore Diameter in mm
Specified size	74.5 + 0.015 +0.005

NOTE:

The cylinder bore must not be measured when the cylinder block is mounted on the Engine and Transmission Holder: VAS6095A because the measurements may be incorrect.