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	mm	0.20…0.40	0.8
Oil scraper ring	mm	0.25…0.50	0.8

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

Piston ring		Clearance
		new	Wear limit
Compression rings	mm	0.06…0.09	0.20
Oil scraper ring	mm	0.03…0.06	0.15

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.

Checking cylinder bores Special tools and workshop equipment required t  Internal dial test indicator 50..100 mm t  Take measurements at 3 positions in both lateral -A-and longitudinal -B- directions, as illustrated. 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.