Piston And Cylinder Bore, Checking

WARNING: This page is about a different car, the 2021 Audi A6 Quattro, 2020 Audi A6 Quattro, and 2019 Audi A6 Quattro. However, it is still accessible from the selected car via links, so may be relevant.

Special tools and workshop equipment required

Cylinder Dial Bore Gauge:VAS6078

Pistons, Checking

Fig 1: Checking Piston Bore

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
Standard dimension	mm	82.42 ¹⁾
¹⁾ Measurement without coating (thickness = 0.02 mm). The coating wears off.

Piston Ring Gap, Checking

Fig 2: Checking Piston Ring Gap

Courtesy of AUDI OF AMERICA, LLC

-- Push the piston ring squarely from above down to approximately 15 mm from the edge of the cylinder. To push in use a piston without rings.

Piston Ring Dimensions in mm	New	Wear Limit
1. Compression ring	0.30 to 0.40	0.80
2. Compression ring	0.40 to 0.50	0.80
Two-piece oil scraping ring	0.20 to 0.40	0.80
Three-piece oil scraping ring	cannot be measured

Piston Ring Groove Clearance, Checking

Fig 3: Checking Piston Ring Groove Clearance

Courtesy of AUDI OF AMERICA, LLC

-- Clean the piston ring groove before checking.

Piston Ring in Connection with the Two-Piece Oil Scraping Ring	New	Wear Limit
1. Compression ring	0.06 to 0.09	0.20
2. Compression ring	0.03 to 0.06	0.15
Oil scraping rings	Cannot be measured

Cylinder Bore, Checking

Fig 4: Checking Cylinder Bore (Dimensions)

Courtesy of AUDI OF AMERICA, LLC

CAUTION:

Risk of damaging the cylinder bore surface through incorrect handling.

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

-- Using a :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
Standard dimension	mm	82.51

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