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

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

2. 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

3. 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

4. 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

5. Oil and Water Plug Installation and Inspect and Clean Lifter Bores • Oil and water plug installation • 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

6. 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

8. 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

9. 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

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

11. 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)

12. 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

13. 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

14. 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

15. Honing After Boring • Machine shop • 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

16. 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

18. 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

19. 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

20. 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

23. 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

24. 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

25. Measuring Bearing Clearance with Plastigage • Bearing clearance • 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

26. 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

27. 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"

28. 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

29. 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

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