Genuine 1992 Audi 100 Piston

1992 Audi 100 Piston Parts and Q&A

• Q: How to remove and inspect the piston in the cylinder head, flywheel, sump, baffle plate, oil pump, and pickup on 1992 Audi 100?

  A: In order to take off the cylinder head, flywheel, sump, baffle plate, oil pump, and pickup, first clean up the tops of the cylinder bores using ridges where the pistons come to top dead centre, and remove all the ridges using a scraper or ridge reamer to avoid damaging the pistons. Determine the big-end to crankpin web thrust clearance at each connecting rod with feeler blades and make a record. Turn the crankshaft until the piston number 1 is at bottom dead centre and label the big-end bearing caps and connecting rods with their number, and be sure to record which way the bearing caps are facing. Unscrew bearing cap bolts or nuts slowly till such that the cap may be removed, retaining the bottom shell bearing and storing it in situations that it is intended to be reused, wherein the shell bearings must be reattached to the same connecting rod. Coat the threaded parts of the bolts with insulating tape so that the crankpins and bores are not damaged when the piston is removed. Forced out by the piston with a bit of dowel, or the handle of a hammer, reclaiming the upper shell bearing and tapping it to cover the connecting rod, not to disturb any of the piston cooling jets. In 4-cylinder engines, take out No 4 piston and connecting rod same, but then turn the crankshaft to take out No 2 and 3 and keep in their respective groups of the engine. Loosen the screws that hold the retaining screws and remove the piston cooling jets, where necessary. When inspecting the pistons, a small flat-bladed screwdriver may be used to prise the gudgeon pin circlips off each piston pushing the gudgeon pin out, discarding the circlips and replacing them with new circlips as required in the reassembly process. Should the pin be hard to get off, dampen the piston in hot water at 60°C before separating it. Installation To install new rings, remove the old ones using a removal tool or an old feeler blade, beginning with the top rings and being careful not to bend them straight off, because new ones need to be installed when reassembling. Cleanse the tops of the pistons with the wire brush or fine emery cloth taking care not to remove the metal, scrape the carbon out of the ring grooves with an old piston ring, and cleanse the tops of the pistons with a brush. Wipe the connecting rods and pistons with paraffin or an adequate solvent, make sure that the oil return holes are free and check for abnormal wear or damage, and a normal wear can look like a vertical grain on the thrust surfaces. Scuffing or scoring can be an indication of overheating, scorch marks are indicative of blow-by and burnt areas of the engine can indicate preignition or detonation. Look at cracks on the pistons, connecting rods, gudgeon pins, and bearing caps, lay the connecting rods on their backs to check the bends or twists and look at the small-end bush bearing wearing. Measure the diameter of all four pistons at a given point with a micrometer and compare the readings with specifications to ascertain the need to have them renewed. Check feeler blade ring to groove clearance by using the proper ring width and in case of out of tolerance clearances then renewal of piston is mandatory. Inspected small-end bearing and gudgeon pin is overworked, and this can lead to a specialist replacing and replacing the bush should be necessary. During the reassembly process, be sure that the piston is properly aligned to the connecting rod, the piston crown arrow should face the timing belt end of the engine and the recesses on both the connecting rod and bearing cap should face the same way. Apply clean engine oil to the gudgeon pin and little-end bush, insert the pin through the piston, connect the connecting rod small-end to it and place new circlips around the piston on either end of the gudgeon pin and repeat the procedure with the remaining pistons.