Engine Diagnosis and Service: Block, Crankshaft, Bearings, and Lubrication System Chapter 53

Objectives Analyze wear and damage to the cylinder block Select and perform the most appropriate repairs to the block, crankshaft, and bearings Analyze wear and damage to the crankshaft and bearings Analyze wear and damage to lubrication system parts Select and perform the most appropriate repairs to the lubrication system

Introduction Cylinder block can usually be reused after certain service procedures are performed Blocks with excessive wear Some will have to be bored oversize to be used with new, larger pistons Some may need only cleaning and minor service Some may need major service

Cleaning the Block and Oil and Water Plug Removal Block must be thoroughly cleaned Removable parts must be removed Oil and water plug removal Female plug: removed by plug driver Male plug: removed with socket Core plugs: knocked out from rear Clean oil galleries and the block Remove deposits in oil galleries and supply holes Check for cracks Check block for cracks in cylinder bores

Oil and Water Plug Installation and Inspect and Clean Lifter Bores Reinstall plugs after cleaning galleries Do not over tighten threaded plugs Pressed-fit oil gallery core plugs installed with red thread lock adhesive Cross-stake outside of core holes with chisel Inspect and clean lifter bores Clean with brake hone turned by hand Do not enlarge the lifter bore

Checking Main Bearing Bore Alignment Heating and cooling of engine block results in misalignment of main bearing bores Bearing bores are checked with dial bore gauge Vertical should not be larger than horizontal Line honing realigns main bores Main caps ground on parting faces Bores aligned by honing to original main bearing bore size Removing too much metal moves the crank shaft up too far into block

Check the Deck Surface for Flatness and Clean All Bolt Holes Clean deck surface of block with whetstone Do not make surface too smooth Check deck surface for flatness Threads in the block must be clean Chase threads with a tap Failure to do this results in leaking head gasket Head bolt holes run into water jackets, so threads may rust Rusted steel is very hard

Inspecting Cylinder Bores Cylinder bores wear in a taper and out-of-round fashion Maximum wear is at 90 degrees to wrist pin Different considerations determine cylinder bore wear limits Taper wear Causes end gaps of piston rings to change as the rings move up and down the cylinder Out-of-round wear Caused by piston rocking on wrist pin at TDC and BDC

Measuring the Bore Several methods Dial bore gauge Telescoping gauge and micrometer Inside micrometer Cylinder dial bore gauge Dial bore gauge More accurate

Deglazing the Cylinder Bore Cylinders become glazed where piston rings contact cylinder wall Glaze removed with lacquer thinner, carburetor cleaner, glaze breaker Drill with rotation speed of 450 rpm recommended for deglazing cylinders Two types of glaze breakers: Spring-loaded glaze breaker Ball-type glaze breaker (flex hone)

Clean the Block of Grit Clean block after glaze breaking or honing Grit left will wear parts Clean with stiff brush and hot soapy water Brush can be used by hand or with air drill Check for cleanliness with clean cloth After cleaning: grit may be in crankcase area Ferrous parts Coated with oil to prevent rusting Rusting begins immediately after cleaning

Boring for Oversized Pistons Cylinders deglazed only if they do not have excessive bore taper Damaged cylinders should be rebored and honed Piston oversizes Top of oversize piston is stamped with oversize amount

Block Distortion Block castings distort when heads and main cap bolts are torqued Distortion results in piston scuffing and slap Boring stand Supports block at main bearing bores Torque plate is sometimes torqued to top of block Stresses the block and simulates assembly conditions Main caps should be torqued in place

Honing After Boring Machine shop Pistons vary in size within a set Bore cylinders to desired bore size Honing after boring provides better surface for new rings Pistons vary in size within a set Must be fitted to the bores After boring and honing Top of bore is chamfered by 1/16” New rings enter cylinder without chipping

Sleeves Sleeves repair cracked or damaged cylinder Recommended interference fit: 0.0005 per inch Sleeve pressed into the bore Top finished flush with block Inside diameter bored to finished size Popular sleeving method Bottom of sleeve rests on step

Cam Bearing Installation (Cam-in-Block Engines) Cam bearings are interference fit Outside diameter larger than bearing bores in the block Clean bearing bores before installing Several types of cam bearing removal and installation tools Universal type installation tool most popular Follow manufacturer’s recommendations when positioning the oil hole

Front Cam Bearing Installation Older pushrod engines Timing sprockets are chain lubricated from front cam bearing Often installed past block surface Oil channel throws oil onto the timing chain Check fit of bearing After installing bearing: install cam and turn it Special flex hone is available for honing small amounts off cam bearings Scotch BriteTM can be used to polish cam bearing surfaces

Checking Crankshaft Condition Check crankshaft for straightness Keep bearings in position order during disassembly Bent crank indicated when one bearing wears more than others Checking for cracks Ring counterweights with light tap of hammer Dull sound indicates crack Crankshaft is broken Check vibration damper for damage

Crankshaft and Bearing Wear Characteristics Bearings have loaded and unloaded halves Main cause of short bearing life is dirt Journals wear out-of-round or become tapered Rod journals exhibit taper wear due to misalignment of connecting rod Thrust bearing wear and failure occur when load is continuous Improper clutch adjustment Driver riding the clutch

Crankshaft Journal Tolerance and Regrinding the Crankshaft Tolerance: range of wear specifications Crankshaft: usually reground undersize Rod journals and main journals may be ground to different undersizes

Measuring Bearing Clearance with Plastigage Checked with plastigage or micrometer Do not rotate crankshaft while plastigage in place Cap is torqued: plastic string flattens Wider string: indicates less clearance Actual clearance Can also be determined by micrometer Some manufacturers use select-fit bearings on new engines Those that have not been previously rebuilt

Lubrication System Service Engine oil pressure Indicates condition of lower end Low pressure at idle indicates excessive clearance or worn pump Long periods of idling with low oil pressure leads to cylinder wall lubrication problems Engine with too much oil pressure Oil consumption problems Bearing lining material washed off

Checking Oil Pumps for Wear Use feeler gauge to check oil pump for wear Follow manufacturer specifications Rotor pump clearance tolerances 0.010" between inside and outside rotors 0.014" between outside rotor and housing Gear pump clearance checked by inserting plastigage between cover and gear ends End clearance less than 0.003" Side clearance less than 0.005"

Oil Pump Screen Service Oil pump screen: check to be sure it’s clean Be sure bypass is not stuck permanently open on newly cleaned screens Screen should not have loose or damaged wire mesh

Oil Pump Failure Causes of pump failure Improper maintenance Foreign objects get into pump Deteriorated valve guide seals Bottom of pump requires gasket only if mounted on outside of block Bolt-on oil pickup screens require gasket Replace screens that do not fit tightly, are damaged, or dirty

Installing the Oil Pump Fill oil pump cavity with lubricant Turn by hand to be sure it is not damaged