Cleaning
1. Remove all external components from the unit, including mounting lugs, engine mounts, water pump, thermoviscous fan shaft assembly, oil filter bracket, high pressure fuel pump bracket, and electrical switches/sensors (see illustrations). For complete cleaning, the cork plugs must also be removed. Drill a small hole in the plugs, then screw self-tapping screws into the holes. Remove the plugs by pulling the screws with pliers.
2. Clean off all traces of gasket and sealant from the cylinder block/crankcase, being careful not to damage the contact surfaces.
3. Remove all oil port plugs (where there are). The plugs are usually very tight - they will probably have to be drilled out and then re-threaded in the crankcase holes. In any case, use new plugs when assembling.
4. If the crankcase is too dirty, have an auto repair shop clean it with steam. After steam cleaning, all oil holes and passages in the crankcase should be flushed. Run warm water through the internal channels until the water that comes out is clear. Dry the channels thoroughly with compressed air and apply a thin layer of oil to all contact surfaces of the block and cylinder walls to prevent corrosion.
Warning: When using compressed air, wear goggles to protect your eyes.
5. If the crankcase is not very dirty, clean it with hot soapy water using a stiff brush. Regardless of the cleaning method used, be sure to thoroughly clean all oil holes and passages, and then dry all components thoroughly. Protect the cylinder walls from corrosion as described above.
6. All tapped holes must be clean so that accurate tightening torques can be achieved during assembly. To clean the threads of each of the holes from rust, deposits or traces of sealant and restore it, run a tap of the appropriate size through it (see illustration). When finished, blow out the holes again with compressed air to clear them of the grains that appeared as a result of this action.
Note: Make sure all threaded holes are free of moisture as the crankcase may crack due to the hydraulic pressure generated when screwing a bolt into a hole containing fluid.
7. Apply a suitable sealant to the new oil port plugs and insert them into the holes in the block. Clamp them securely.
8. If the engine will not be assembled immediately, cover it with a large plastic bag to keep it clean; lubricate all contact surfaces and cylinder walls with oil to prevent corrosion.
Inspection
9. Inspect crankcase parts for cracks and corrosion. Check the integrity of the threads in the holes. If there are signs of an internal coolant leak, have a technician diagnose the unit using special equipment. If defects are found, repair (if it is possible) or replace the assembly.
10. Check the walls of each cylinder for nicks and notches. If this type of damage is found, inspect the corresponding piston (see Chapter 7 of this Section). If the damage is not deep, it may be possible to restore the block by boring the cylinders. Seek advice from a specialist.
11. To make an accurate assessment of the wear of the cylinder walls, measure their diameter at several points as follows. Insert the inside gauge into cylinder No. 1 and make three measurements parallel to the crankshaft axis - 10 mm from the top edge of the cylinder, in the middle part of the cylinder and 10 mm from its bottom edge.
Note: To perform this procedure, place the cylinder block on a workbench. If measurements are taken on a motor mounted on a base, inaccurate results may be obtained.
12. Rotate the inside gauge 90° (perpendicular to the axis of the crankshaft) and repeat measurements (see illustration). Record the results of all six measurements and compare them with the data given in the Specifications. If the difference between the diameters of any two cylinders exceeds the wear limit, or if the diameter of at least one of the cylinders exceeds the limit, it is necessary to bore all four cylinders and install oversize pistons.
13. Using the piston diameter data recorded earlier (see chapter 7), calculate the clearance between the piston and the cylinder wall. Manufacturers do not give any values for this clearance, so consult your Audi dealer for advice.
14. Place the block of cylinders on a workbench crankcase down. Using the edge of a ruler and a set of feeler gauges, measure the deformation of both contact surfaces of the cylinder head. Manufacturers do not give the maximum allowable value, but approximately it is 0.05 mm. If the amount of deformation exceeds this figure, it may be possible to regrind the block - consult your dealer.
15. Before the engine can be assembled, the cylinder walls must be honed, i.e. apply fine hatching on them with an abrasive tool. This is done so that the new piston rings get used to the cylinder walls. Two types of honing tools are available, both driven by an electrically driven rotary tool such as a drill. There are two types of hone - flexible, bottle brush type, and hone with spring-loaded heads. A less experienced mechanic will probably find it easier to work with a flexible hone. In addition, you will need kerosene or special oil, rags, an electric drill and safety glasses.
Note: If you don't want to do the honing of the cylinders yourself, have the job done by an auto repair shop.
16. Perform honing as follows.
17. Install hone on the drill. Lubricate the cylinders generously with honing oil, squeeze the honing heads and push them into the first cylinder. Turn on the drill and move the hone in the cylinder up and down at a speed that will allow you to apply fine hatching on the walls. Ideally, hatch lines should intersect at an angle of approximately 60° (see illustration). Some piston ring manufacturers may specify hatch angles less than the traditional 60°- read the instructions that come with the rings and follow them carefully.
Note: When working with the hon, protect your eyes with goggles.
18. Be sure to use enough lube and don't remove more metal than absolutely necessary. Do not remove the hone from the cylinder while it is rotating. Unplug the drill and keep moving the hone up and down until it stops, then squeeze the heads and pull out the hone. If a flexible hone is used, stop the drill, then remove the hone from the cylinder by turning it in the direction of rotation.
19. Wipe off oil and small metal chips with a rag and move on to the next cylinder. When all four cylinders are honed, wash the cylinder block thoroughly in hot, soapy water. The cylinder can be considered clean when, after passing a thick white cloth over its wall, (lint-free), moistened with clean engine oil, the cloth remains clean. Be sure to brush out all oil holes and passages and flush them with water.
20. Rinse the block with clean water, dry it, and coat all machined surfaces and cylinder walls with engine oil to prevent corrosion.
21. Install all components removed in step 1.
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