Piston And Cylinder Bore, Checking

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Fig 1: Checking Pistons

Courtesy of AUDI OF AMERICA, LLC

-- Measure approximately 15 mm from the lower edge at a 90° angle to the piston pin axis using a 75 to 100 mm external micrometer.

Deviation from specified size: maximum 0.04 mm

		Piston Diameter
Basic dimension	mm	82.465 ¹⁾
¹⁾ Measurements without graphite coating (thickness = 0.02 mm). The graphite coating wears off.

Fig 2: Checking Piston Ring Gap

Courtesy of AUDI OF AMERICA, LLC

-- Push piston ring squarely from above down to approximately 15 mm from bottom end of cylinder. To do this use a piston without rings.

Piston Ring Dimensions in mm	New	Wear Limit
Compression ring	0.20 to 0.40	0.80
Oil scraping ring	0.25 to 0.50	0.80

Fig 3: Checking Piston Ring Groove Clearance

Courtesy of AUDI OF AMERICA, LLC

-- Clean the ring groove of piston before checking.

Piston Ring Dimensions in mm	New	Wear Limit
1st Compression ring	0.06 to 0.09	0.20
2nd Compression ring	0.03 to 0.06	0.15
Oil scraping rings	Cannot be measured

Fig 4: Checking Cylinder Bores

Courtesy of AUDI OF AMERICA, LLC

Special tools and workshop equipment required

Cylinder Dial Bore Gauge VAS6078

NOTE:

A shadow or a shiny spot on the wall of the cylinder does not mean the cylinder bore is damaged as long as the cross-grinding is still visible.

Always measure the cylinder bore in 3 places laterally and longitudinally using Cylinder Dial Bore Gauge VAS6078.

CAUTION:

Do not bore, hone, grind or rework the cylinder bores with shop tools. Reworking damages the surface of the cylinder bore.

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

Deviation from specified size: maximum 0.08 mm

		Cylinder Bore Diameter
Basic dimension	mm	82.51

NOTE:

The cylinder bore must not be measured when the cylinder block is mounted on the Engine and Transmission Holder VAS6095 because the measurements may be incorrect.