Volkswagen Golf Service & Repair Manual: Checking pistons and cylinder bores

Volkswagen Golf Service & Repair Manual / 4- cylinder injection engine(1.4 1 direct inction. turbocharger) / Enginecrankshaft group, pistons / Pistons and conrods / Checking pistons and cylinder bores

Checking piston

–	Using a micrometre, measure approx. 10 mm from the lower edge, perpendicular to the piston pin axis.

Maximum deviation from nominal dimension: 0.04 mm

Checking pistons and cylinder bores

Piston diameter mm

Specification

74.42 ¹⁾

¹⁾ Dimensions without coating

Piston manufacturer Federal Mogul (thickness of 0.018 mm per side)

Piston manufacturer Mahle (thickness of 0.015 mm per side)

Measuring piston ring gap

–	Push piston ring at right angles to cylinder wall from above down into cylinder bore to approx. 15 mm from bottom end of cylinder.

–	Push in using a piston without piston rings.

Checking pistons and cylinder bores

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

Measuring ring-to-groove clearance

–	Clean annular groove of piston before check.

Checking pistons and cylinder bores

Piston ring	New mm	Wear limit mm
1st compression ring (piston ring manufacturer Federal Mogul)	0.050 … 0.090	0.15
1st compression ring (piston ring manufacturer Mahle)	0.035 … 0.085	0.15
2nd compression ring	0.030 … 0.070	0.15
Oil scraper rings (3 parts)	Not measurable
Oil scraper rings (2 parts)	0.04 … 0.08

Measuring cylinder bore

Risk of damage to the surface of the cylinder bore caused by incorrect machining.Do not machine cylinder bore (reboring, honing, grinding) with workshop equipment.

–	Using cylinder gauge -VAS 6078- take measurements at 3 positions diagonally in lateral direction -A- and longitudinal direction -B-.

Maximum deviation from nominal dimension: 0.08 mm

Checking pistons and cylinder bores

Cylinder bore diameter mm
Specification	74.5 + 0.015 ¹⁾ +0.005

Note

Cylinder bores must not be measured when cylinder block is mounted on engine and gearbox support -VAS 6095-, as measurements may be incorrect.

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