Checking cylinders, pistons and piston rings (VW Caddy 3)

Checking the thermal clearance of piston rings

Place the ring on top of the cylinder and then slide it down to the bottom of the cylinder so that it is positioned approximately 15mm from the bottom edge of the cylinder (using an old piston).

Piston ring	Thermal gap
	New	Maximum permissible value
Compression rings	0,20-0,40	0,8
Oil scraper ring	0,25-0,50	0,8

Checking the height clearance between the groove and the ring

The original article is available at (VWMANUAL)

Before checking, clean the groove in the piston.

Piston ring	Height clearance between groove and ring
	New	Maximum permissible value
Compression rings	0.06-0.09 mm	0.20 mm
Oil scraper ring	0.03-0.06 mm	0.15 mm

Measure at a right angle to the longitudinal axis of the cylinder, approximately 10 mm above the lower edge of the piston skirt.

Deviations from nominal dimensions are no more than 0.04 mm.

Checking the cylinder diameter

Take measurements crosswise in three places in the transverse (A) and longitudinal (B) directions.

Deviations from nominal dimensions are no more than 0.08 mm.

Caution! Do not measure cylinder diameters on an engine mounted on an assembly stand, as this may distort the measurement results due to deformation of the cylinder block under its own weight.

Piston and cylinder dimensions:

• Nominal piston size: 80.965 mm*.
• Nominal cylinder size: 81.01 mm*.

* Dimensions without graphite coating (thickness 0.02 mm). The graphite coating wears off at the beginning of use.