Volkswagen Workshop Service and Repair Manuals

Checking pistons, piston rings and cylinder bores

Checking piston ring gap Special tools and workshop equipment required t  Feeler gauges Test sequence: –  Push ring squarely from above down to approx. 15 mm from bottom end of cylinder.

Piston ring		Gap
		New	Wear limit
Compression rings (top)	mm	0.15…0.35	0.8
Compression rings (bottom)	mm	0.40...0.40	0.8
Oil scraper ring	mm	0.20…0.70	0.9

Checking ring-to-groove clearance Special tools and workshop equipment required t  Feeler gauges Clean groove before check.

Piston ring		Ring-to-groove clearance
		New	Wear limit
Top compression rings	mm	0.04…0.075	0.15
Middle compresion rings	mm	0.02...0.055	0.15
Oil scraper ring	mm	0.05…0.13	0.20

Checking piston Special tools and workshop equipment required t  External micrometer 75...100 mm Measure pistons approx. 10 mm from the lower edge of skirt, at 90° to the piston pin axis. Deviation from nominal dimension max. 0.04 mm.

Bearing shells - installation position Bearing shell -1- with oil hole -arrow- for conrod. Bearing shell -2- without oil hole for conrod bearing cap. –  Fit bearing shells in centre of conrod and conrod cap. Dimension -a- must be the same on the left and right, max. deviation: 0.2 mm.

Checking cylinder bores Special tools and workshop equipment required t  Cylinder gauge 50...100 mm t  Measure at 3 positions both across -A- and in-line with engine -B- t  Deviation from nominal dimension max. 0.08 mm   Note Cylinder bores must not be measured when cylinder block is mounted on a repair stand with engine and gearbox support -VW 540-, as measurements may then be incorrect.