Genuine 2002 Volkswagen Cabrio Piston

2002 Volkswagen Cabrio Piston Parts and Q&A

• Q: How to check the oil clearance of the connecting rod bearing on a Piston on 2002 Volkswagen Cabrio?

  A: In order to measure the oil clearance of the connecting rod bearing, make sure that the crankshaft is in place. Between the oil crankpin of the connecting rod and the two bearing shells, there must be a clearance which is essential to the circulation of the oil, and the clearance may be measured in two ways. Work Starting with the cylinder block on a flat surface which is clean and level, with crankcase facing upwards and with the crankshaft in place such that the crankpins No. 1 and 4 appear at BDC. The former is by attaching the bearing caps to the connecting rods not touching the crankshaft so that the caps are in the right position, and that the internal diameter created by the assembled rod is measured using internal vernier calipers. Determine the crankpin diameter and subtract it to the measurement to determine the oil clearance. The second procedure involves the use of Plastigage to have a more precise measure. Clean the crankpins, put a strand of Plastigage on each crankpin journal, fit the upper bearing shells and begin fitting the piston/connecting rod assemblies in place temporarily on the crankshaft. Close the bearing cap nuts/bolts with great care and do not disturb the Plastigage. Following disassembly, check the big-end bearing running clearance with the Plastigage scale and compare the results with the expected values. When discrepancies appear, re-check crankpin diameters, dirt or oil between parts, etc. Where a requirement arises, fit new bearing shells or re-grind crankpins. Following verification, take out all Plastigage material. To have the piston and connecting rod assemblies installed finally, bearings shells must be properly in place, and not covered with protective grease. Wipe the bores, pistons, and rings of the cylinder with clean engine oil, and position each part accordingly. Beginning with assembly No. 1, follow the same steps as described below: Assembly No. 1: Clamp the piston rings with compressor then place the assembly into the cylinder with the proper orientation. Assemble by tapping the assembly, lubricating crankpin and bearing shells, and attaching bearing cap by tightening nuts / bolts in that order. Do the same with the other assemblies and make sure that the crankshaft is free. In the case of diesel engines, when new pistons are to be fitted or a new short block is being fitted, the measurement taken of the projection of the piston crowns above the cylinder head at TDC should be taken in order to select the right type of head gasket. Rotate the cylinder block and clamp a dial indicator and measure the highest deflection at TDC with each piston where the maximum deflection is recorded, use the highest value to choose the type of head gasket. In case of original pistons, place a new head gasket of the same type as the initial one.