Chapter 1 Routine maintenance and servicing

Engine removal and overhaul procedures 2D•21diameter from the bore measurement. If theprecision measuring tools shown are notavailable, the condition of the pistons andbores can be assessed, though not quite asaccurately, by using feeler gauges as follows.Select a feeler gauge of thickness equal to thespecified piston-to-bore clearance, and slip itinto the cylinder along with the matchingpiston. The piston must be positioned exactlyas it normally would be. The feeler gaugemust be between the piston and cylinder onone of the thrust faces (at right-angles to thegudgeon pin bore). The piston should slipthrough the cylinder (with the feeler gauge inplace) with moderate pressure; if it fallsthrough or slides through easily, the clearanceis excessive, and a new piston will berequired. If the piston binds at the lower endof the cylinder, and is loose toward the top,the cylinder is tapered. If tight spots areencountered as the piston/feeler gauge isrotated in the cylinder, the cylinder isout-of-round (oval).15 Repeat these procedures for theremaining pistons and cylinder bores.16 Compare the results with theSpecifications at the beginning of thisChapter; if any measurement is beyond thedimensions specified for that class (check thepiston crown marking to establish the classof piston fitted), or if any bore measurement issignificantly different from the others(indicating that the bore is tapered or oval),the piston or bore is excessively-worn.17 Worn pistons must be renewed; on someengines, the pistons are available as Fordreplacement parts only as part of thecomplete piston/connecting rod assembly.See a Ford dealer or engine reconditioningspecialist for advice.18 If any of the cylinder bores are badlyscuffed or scored, or if they are excessivelyworn,out-of-round or tapered, the usualcourse of action would be to have the cylinderblock/crankcase rebored, and to fit new,oversized, pistons on reassembly. See a Forddealer or engine reconditioning specialist foradvice.19 If the bores are in reasonably goodcondition and not excessively-worn, then itmay only be necessary to renew the pistonrings.20 If this is the case, the bores should behoned, to allow the new rings to bed incorrectly and provide the best possible seal.Honing is an operation that will be carried outfor you by an engine reconditioning specialist.21 After all the machining operations havebeen carried out, the entire block/crankcasemust be washed very thoroughly with warmsoapy water to remove all traces of abrasivegrit produced during the machiningoperations. When completely clean, rinse itthoroughly and dry it, then lightly oil allexposed machined surfaces to preventrusting.22 The cylinder block/crankcase should nowbe completely clean and dry, with allcomponents checked for wear or damage,and repaired or overhauled as necessary.Refit as many ancillary components aspossible, for safekeeping. If reassembly is notto start immediately, cover the block with alarge plastic bag to keep it clean.14 Main and big-end bearings -inspection41 Even though the main and big-end bearingshells should be renewed during the engineoverhaul, the old shells should be retained forclose examination, as they may revealvaluable information about the condition ofthe engine (see illustration).2 Bearing failure occurs because of lack oflubrication, the presence of dirt or otherforeign particles, overloading the engine, andcorrosion. Regardless of the cause of bearingfailure, it must be corrected before the engineis reassembled, to prevent it from happeningagain.3 When examining the bearing shells, removethem from the cylinder block/crankcase andmain bearing caps, and from the connectingrods and the big-end bearing caps, then laythem out on a clean surface in the samegeneral position as their location in theengine. This will enable you to match anybearing problems with the correspondingcrankshaft journal. Do not touch any shell’sbearing surface with your fingers whilechecking it, or the delicate surface may bescratched.4 Dirt or other foreign matter gets into theengine in a variety of ways. It may be left inthe engine during assembly, or it may passthrough filters or the crankcase ventilationsystem. It may get into the oil, and from thereinto the bearings. Metal chips from machiningoperations and normal engine wear are oftenpresent. Abrasives are sometimes left inengine components after reconditioning,especially when parts are not thoroughlycleaned using the proper cleaning methods.Whatever the source, these foreign objectsoften end up embedded in the soft bearingmaterial, and are easily recognised. Largeparticles will not embed in the material, andwill score or gouge the shell and journal. Thebest prevention for this cause of bearingfailure is to clean all parts thoroughly, and tokeep everything spotlessly-clean duringengine assembly. Frequent and regular engineoil and filter changes are also recommended.5 Lack of lubrication (or lubricationbreakdown) has a number of inter-relatedcauses. Excessive heat (which thins the oil),overloading (which squeezes the oil fromthe bearing face) and oil leakage (fromexcessive bearing clearances, worn oil pumpor high engine speeds) all contribute tolubrication breakdown. Blocked oil passages,which usually are the result of misaligned oilholes in a bearing shell, will also starve a14.1 Typical bearing failuresbearing of oil, and destroy it. When lack oflubrication is the cause of bearing failure, thebearing material is wiped or extruded from theshell’s steel backing. Temperatures mayincrease to the point where the steel backingturns blue from overheating.6 Driving habits can have a definite effect onbearing life. Full-throttle, low-speed operation(labouring the engine) puts very high loads onbearings, which tends to squeeze out the oilfilm. These loads cause the shells to flex,which produces fine cracks in the bearingface (fatigue failure). Eventually, the bearingmaterial will loosen in pieces, and tear awayfrom the steel backing.7 Short-distance driving leads to corrosion ofbearings, because insufficient engine heat isproduced to drive off condensed water andcorrosive gases. These products collect in theengine oil, forming acid and sludge. As the oilis carried to the engine bearings, the acidattacks and corrodes the bearing material.8 Incorrect shell refitting during engineassembly will lead to bearing failure as well.Tight-fitting shells leave insufficient bearingrunning clearance, and will result in oilstarvation. Dirt or foreign particles trappedbehind a bearing shell result in high spots onthe bearing, which lead to failure.9 Do not touch any shell’s bearing surfacewith your fingers during reassembly; there is arisk of scratching the delicate surface, or ofdepositing particles of dirt on it.15 Engine overhaul -reassembly sequence1 Before reassembly begins ensure that allnew parts have been obtained and that allnecessary tools are available. Read throughthe entire procedure to familiarise yourself withthe work involved, and to ensure that all items2D1595Ford Fiesta Remake