Halderman ch029 lecture

© 2011 Pearson Education, Inc.All Rights Reserved

Automotive Technology, Fourth EditionJames Halderman

ENGINE CLEANING AND CRACK DETECTION

29

29 ENGINE CLEANING AND CRACK DETECTION



ObjectivesObjectives

• The student should be able to:– Prepare for ASE Engine Repair (A1)

certification test content area “A” (General Engine Diagnosis).

– List the types of engine cleaning methods. – List the various methods that can be used

to check engine parts for cracks. – Describe crack repair procedures.




INTRODUCTIONINTRODUCTION




IntroductionIntroduction

• After disassembly, all engines must go through two operations– All parts thoroughly cleaned– All parts inspected to ensure they are free

from faults such as cracks




MECHANICAL MECHANICAL CLEANINGCLEANING




Mechanical CleaningMechanical Cleaning

• Principles– Remove heavy deposits by scraping,

abrasive brushing, abrasive blasting





• Scraping– Putty knife most frequently used

• Broad blade avoids scratching surface of parts

– Plastic card used to clean aluminum parts





• Abrasive Pads or Discs– Used on disassembled parts only– Do not use steel wire brushes on aluminum

parts





• Abrasive Pads or Discs– After use, clean part to remove particles

from pad or disc• White disc: finest grit• Yellow disc: coarse grit• Green disc




Figure 29-1 An air-powered grinder attached to a bristle pad being used to clean the gasket surface of a cylinder head. This type of cleaning pad should not be used on the engine block where the grit could get into the engine oil and cause harm when the engine is started and run after the repair.




Figure 29-2 An abrasive disc commonly called by its trade can be engine damaging. name, Scotch Brite™ pad.





• Media Blasting– Media blasting with baking soda cleaning

method of choice• Nontoxic• Nonflammable• Nonhazardous• Environmentally safe





• Media Blasting– Soda blasting machine uses compressed air

to clean part– Cleaning with solvents or heat requires

second operation for uniform surface finish• Blast part with stainless steel shot, baking

soda, or glass beads





• Media Blasting– Cleaning with solvents or heat requires

second operation for uniform surface finish• Achieves matte or satin finish on part• Blasting particles must be absolutely dry so

won’t stick to part




Figure 29-3 Using baking soda is the recommended way to clean engine parts because any soda that is left on or in the part is dissolved in oil or water, unlike either sand or glass beads, which can be engine damaging.




Figure 29-4 Small engine parts can be blasted clean in a sealed cabinet.




CHEMICAL CLEANERSCHEMICAL CLEANERS




Chemical CleanersChemical Cleaners

• pH– Chemical cleaners used on carbon-type

deposits are strong soaps– pH value indicates amount of chemical

activity in soap





• pH– Measured on a scale from 1 to 14– Pure water neutral (pH of 7)





• pH– Caustic materials have pH of 8 to 14

• Higher number, stronger caustic action





• pH– Acid materials have pH of 1 to 6

• Lower number, stronger acid action





• pH– Caustic and acid materials neutralize each

other• Baking soda (caustic) used to clean outside

of battery (acid)

– Use eye protection whenever working with chemicals





• Solvent-Based Cleaning– Cleaning chemicals mix with and dissolve

deposits– Loosen deposits so they can be brushed or

rinsed from surface





• Solvent-Based Cleaning– Can involve spray washer or a soak in cold

or hot tank– Also contain silicates to protect aluminum

against corrosion





• Solvent-Based Cleaning– Strong caustics excellent for cast-iron items– Mineral spirit solvents and alkaline

detergents used for aluminum





• Water-Based Chemical Cleaning– Most chemical cleaning now uses water-

based solutions– May be sprayed on or used in soaking

tanks– Aluminum heads and blocks usually require

overnight soaking




SPRAY AND STEAM SPRAY AND STEAM WASHINGWASHING




Spray and Steam WashingSpray and Steam Washing

• Spray Washing– High-pressure washer dislodges dirt and

grime from engine surface– Typically performed in an enclosed washer– Faster than soaking




Figure 29-5 A pressure jet washer is similar to a large industrialsized dishwasher. Each part is then rinsed with water to remove chemicals or debris that may remain there while it is still in the tank.





• Steam Cleaning– Steam vapor mixed with high-pressure

water and sprayed on parts– Heat of steam plus force of water perform

cleaning





• Steam Cleaning– Must be used with extreme care– Usually caustic cleaner added as well– Mixture so active that can remove paint




THERMAL CLEANINGTHERMAL CLEANING




Thermal CleaningThermal Cleaning

• Temperatures Involved– Heat vaporizes and changes dirt, oil, and

grease into dry, powdery ash– Best suited for cast iron, temperatures as

high as 800°F (425°C)– Aluminum should not be heated to over

600°F (315°C)





• Advantages– Cleans inside as well as outside of casting

or part– Waste generated is nonhazardous and is

easy to dispose of





• Microbial Cleaning– Microbes that “eat” hydrocarbons off of

parts– Environmentally friendly, but slower to

clean parts




Figure 29-6 A microbial cleaning tank uses microbes to clean grease and oil from parts.





• Pyrolytic Oven– Decomposes dirt, grease, and gaskets with

heat like self-cleaning oven– Least hazardous method– Becoming most popular because no

hazardous waste




Figure 29-7 (a) A pyrolytic (high-temperature) oven cleans by baking the engine parts. After the parts have been cleaned, they are then placed into an airless blaster. This unit uses a paddle to scoop stainless steel shot from a reservoir and forces it against the engine part. The parts must be free of grease and oil to function correctly.




Figure 29-7 (b) This cleaned engine block has been baked and shot blasted.




TANK AND VAPOR TANK AND VAPOR CLEANINGCLEANING




Tank and Vapor CleaningTank and Vapor Cleaning

• Cold Tank Cleaning– Removes grease and carbon– Disassembled parts completely covered by

solution in tank





• Cold Tank Cleaning– After soaking, parts are rinsed– Parts may be covered with thin layer of oil

to prevent rusting





• Cold Tank Cleaning– Parts washers often used in place of

soaking tanks– May pump cleaning solution over parts to

help remove dirt





• Hot Tank Cleaning– For cleaning heavy organic deposits and

rust from iron and steel parts– Caustic cleaning solution heated to near

200°F (93°C)– Rapid cleaning action





• Vapor Cleaning– Parts suspended in hot vapors above

perchloroethylene solution– Vapors of solution loosen soil from metal – Soil can be blown, wiped, or rinsed from

surface




ULTRASONIC ANDULTRASONIC ANDVIBRATORY CLEANINGVIBRATORY CLEANING




Ultrasonic and Vibratory CleaningUltrasonic and Vibratory Cleaning

• Ultrasonic Cleaning– Used to clean small parts that must be

absolutely clean– Parts placed in cleaning solution that is

vibrated at ultrasonic speeds– Soil is loosened and falls into solution




Figure 29-8 An ultrasonic cleaner being used to clean fuel injectors.




Ultrasonic and Vibratory CleaningUltrasonic and Vibratory Cleaning

• Vibratory Cleaning– Best suited for small parts– Parts loaded into a vibrating bin with media

and cleaning solution– Movement of vibrating solution and

scrubbing action of media clean metal




CRACK DETECTIONCRACK DETECTION




Crack DetectionCrack Detection

• Visual Inspection– After cleaning, reexamine parts for faults– Use magnifying glass





• Visual Inspection– Internal parts with cracks should be

replaced– Cracks in blocks and heads can be repaired





• Magnetic Crack Detection– Commonly called by brand name:

Magnafluxing– Method most often used on steel and iron

components





• Magnetic Crack Detection– Part connected to strong electromagnet– Magnetic lines of force concentrate on the

edges of a crack– Fine iron powder applied, attracted to

magnetic concentration




Figure 29-9 The top deck surface of a block is being tested using magnetic crack inspection equipment.




Figure 29-10 If the lines of force are interrupted by a break (crack) in the casting, then two magnetic fields are created and the powder will lodge in the crack.




Figure 29-11 This crack in a vintage Ford 289, V-8 block was likely caused by the technician using excessive force trying to remove the plug from the block. The technician should have used heat and wax, not only to make the job easier, but also to prevent damaging the block.





• Dye-Penetrant Testing– Often used on pistons and other parts

made of nonmagnetic material– Dark red penetrating chemical sprayed on

component





• Dye-Penetrant Testing– After cleaning, white powder sprayed over

test area– If crack present, red dye will stain white

powder





• Fluorescent-Penetrant Testing– Requires a black light– Can be used on iron, steel, or aluminum

parts– Cracks show up as bright lines when

viewed with a black light





• Pressure Testing– Cylinder heads and blocks often pressure

tested with air– Check for leaks




Figure 29-12 To make sure that the mark observed in the cylinder wall was a crack, compressed air was forced into the water jacket while soapy water was sprayed on the cylinder wall. Bubbles confirmed that the mark was indeed a crack.




Figure 29-13 A cylinder head is under water and being pressure tested using compressed air. Note that the air bubbles indicate a crack.




Crack RepairCrack Repair

• Crack Concerns– Cracks in engine block can allow coolant

and oil to mix– Cracks in head allows coolant to leak into

engine




CRACK REPAIRCRACK REPAIR





• Crack Concerns– Cracks in head allows combustion gases to

leak into coolant– Cracks across valve seat cause hot spots

on valve– Head with crack has to be replaced or

repaired





• Stop Drilling– Hole drilled at each end of crack to keep it

from extending farther– Cracks cannot cross oil passages, bolt

holes, or seal surfaces





• Crack-Welding Cast Iron– Takes great skill to weld cast iron– Can be done satisfactorily when entire cast

part is heated red-hot– New technique involves flame welding

using special torch




Figure 29-14 (a) Before welding, the crack is ground out using a carbide grinder.




Figure 29-14 (b) Here the technician is practicing using the special cast-iron welding torch before welding the cracked cylinder head.




Figure 29-14 (c) This is the finished welded crack before final machining.




Figure 29-14 (d) Note the finished cylinder head after the crack has been repaired using welding.





• Crack-Welding Aluminum– Aluminum can be welded using a special

Heli-arc or similar welder– Crack cut or burned out before welding





• Crack Plugging– Crack closed using interlocking tapered

plugs– Used in both aluminum and cast-iron

engine components





• Crack Plugging– Ends of crack center punched and drilled– Hole reamed with tapered reamer





• Crack Plugging– Hole then tapped with special tap to give

full threads– Plug coated with sealer and tightened into

hole; excess broken off





• Crack Plugging– Next hole drilled to interlock with preceding

plug– Process continues to fill crack– Surface of plugs ground down to level with

original surface




Figure 29-15 Reaming a hole for a tapered plug.




Figure 29-16 Tapping a tapered hole for a plug.




Figure 29-17 Screwing a tapered plug in the hole.




Figure 29-18 Cutting the plug with a hacksaw.




Figure 29-19 Interlocking plugs.




Figure 29-20 (a) A hole is drilled and tapped for the plugs.




Figure 29-20 (b) The plugs are installed.




Figure 29-20 (c) After final machining, the cylinder head can be returned to useful service.

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