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EXAMPLE STUDY A four-cylinder engine is brought into the shop. The customer complains of excessive oil consumption and oil leaks. Compression and cylinder leakage tests indicate that the cylinders are sealing well, and a power balance test indicates that all of the cylinders are producing about the same amount of power. Based on these results, the technician assumes that the problem is leaking valve seals. The initial plan is to replace the seals and re-gasket the engine. It’s odd that the engine has both of these problems. It has less than 50,000 miles on it. Not really sure if the problems are related, the technician proceeds to disassemble the engine. Upon removing the valve cover, large amounts of sludge are evident throughout the valve train. This is normally a sign that the engine has been neglected. However, a review of the files indicates that the oil has recently been changed. In fact, the car has been well maintained. Is the sludging related to the oil consumption and leaks? The oil pan is removed and additional sludge is found. The cylinder head is then removed from the block. The piston tops and the combustion chamber are covered with a thick black carbon coating. Is this buildup related to other problems? The cylinder head is disassembled and each of the valve seals is found to be deteriorated. What could cause the deterioration of rubber parts, leaking gaskets, sludging, and carbon buildup in the cylinders? After careful thought, the technician pays attention to the parts taken off the engine during initial disassembly. A thorough inspection is made of the PCV system and it’s discovered that the hose that connects the valve to the manifold is plugged solid. The valve is also found to be plugged. The PCV system is designed to remove crankcase fumes and pressure from the crankcase. These fumes can cause rapid sludging of the oil and deterioration of rubber parts. Excessive crankcase pressure can cause leaks, as the pressure seeks to relieve itself. A faulty PCV valve can cause all of the problems exhibited by this engine. In fact, it’s the cause of the problems. The engine is resealed and new valve stem seals are installed. The engine is then installed with a new PCV valve and hose. Not only is the customer's complaint taken care of, but so is the cause of the problem. TERMS Caustic soda; Freewheeling engines; Interference engines Organic soils; Peening; Rust; Salt bath Scale Solvent tank Ultrasonic cleaning Water soluble SUMMARY ¦ When preparing an engine for removal and disassembly, it’s important to always follow the specific service manual procedures for the particular vehicle being worked on. ¦ A hoist and chain are needed to lift an engine out of its compartment. Mount the engine to an engine stand with a minimum of four bolts, or set it securely on blocks. ¦ While an engine teardown of both the cylinder head and block is a relatively standard procedure, exact details vary among engine types and styles. The vehicle's service manual should be considered as the final word. ¦ An understanding of specific soil types can save time and effort during the engine cleaning process. The main categories of contaminants include water-soluble and organic soils, rust, and scale. ¦ Protective gloves and goggles should be worn when working with any type of cleaning solvent or chemical. Read the label carefully before using as well as all of the information provided on material safety data sheets. ¦ Parts washers, or solvent tanks, are a popular and inexpensive means of cleaning the metal surfaces of many automotive components and engine parts. Regardless of the type of solvent used, it usually requires some brushing, scraping, or agitation to increase the cleaning effectiveness. ¦ Cold soak tanks are used to clean carburetors, throttle bodies, and aluminum parts. Hot soak tanks, which can accommodate an entire engine block, use a heated cleaning solution to boil out dirt. Hot heat spray washers have the added benefit of moderate pressure cleaning. ¦ Alternatives to caustic chemical cleaning have emerged in recent years, including ultrasonic cleaning, salt baths, and citrus chemical cleaning. These methods are all growing in popularity. ¦ The main advantage of thermal cleaning is its total reduction of all oils and grease. The high temperatures inside the oven leave a dry, powdery ash on the parts. This is then removed by shot blasting or washing. ¦ Steel shot and glass beads are used for cleaning operations where etching or material removal is not desired. Grit, the other type of abrasive blaster, is used for more aggressive cleaning jobs. ¦ Some degree of manual cleaning is necessary in any engine rebuilding job. Very fine abrasive paper should be used to remove surface irregularities. A handheld or power wire brush is also helpful, though it can be time-consuming to work with. ¦ There are three common methods for detecting cracks in the metal casting of engine parts: using a magnet and magnetic powder (iron filings), using penetrant dye (especially for aluminum heads and blocks), and pressuring with air. EXAM 1. What should be worn when working with any type of cleaning solvent or chemical? 2. True or False? Most engines in a RWD vehicle must be removed with the transmission still attached. 3. What is the best way to lift a vehicle when preparing to remove an engine? a. frame contact hoist b. drive on lift c. hydraulic jack and safety stands d. engine hoist 4. True or False? The first step in disassembling an engine is usually the removal of the intake and exhaust manifolds. 5. Which of the following statements is not true? a. When the engine is removed through the bottom of the vehicle, use an engine cradle and dolly to support the engine. b. If the manufacturer recommends engine removal through the hood opening, use an engine hoist. c. Regardless of the method of removal, the engine and transaxle in a FWD vehicle are usually removed as a unit. d. The transaxle can be separated from the engine after the engine is off its mounts. 6. The buildup of minerals and deposits inside the cooling system is called . a. organic soil c. rust b. scale d. grime 7. Hydrocarbon solvents are . a. flammable c. both a and b b. toxic d. neither a nor b 8. True or False? On many FWD vehicles, the suspension system must be partially disassembled to remove the radiator. 9. Which cleaning method uses high-frequency sound waves to create microscopic bubbles that loosen dirt from parts? a. ultrasonic c. thermal b. salt bath d. caustic 10. Parts must be when they go into an abrasive blast machine. a. wet c. grease-free b. dry d. both b and c 11. An engine block should be mounted to an engine stand using a minimum of bolts. a. four c. three b. six d. five 12. Which of the following is not considered part of the organic soil grouping? a. petroleum by-products derived from crude oil, including tar, road oil, engine oil, gasoline, diesel fuel, grease, and engine oil additives b. rust that is a product of coolant and aluminum c. by-products of combustion, including carbon, varnish, gum, and sludge d. coatings, including such items as rust-proofing materials, gasket sealers and cements, paints, waxes, and sound-deadener coatings 13. Why should a memory saver be installed before disconnecting a vehicle's battery? 14. Which of the following statements is not true about thermal cleaning? a. The main advantage of thermal cleaning is a total reduction of all oils and grease on and in blocks, heads, and other parts. b. After a part has been thermally cleaned, it should be submerged in water to cool it quickly. c. Thermal cleaning leaves behind a dry, powdery ash on the parts. d. After a part has been thermally cleaned, it should be washed or blasted with shot. 15. Which of the following is not a common way to identify the location of cracks in the engine block or cylinder head? a. pressure checks b. vacuum test c. magnetic particle inspection d. penetrant dye ASE-STYLE REVIEW QUESTIONS 1. While working on an engine with an excessive amount of sludge buildup: Technician A says that the presence of sludge is a signal to look for wear on other components. Technician B says that excessive buildup can indicate a poor maintenance schedule. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 2. While discussing the common causes for cracks developing in a cylinder block or head: Technician A says that the chilling of a hot engine by a sudden rush of cold water or air over the surface may cause cracking. Technician B says that excessive overheating is a common cause. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 3. Technician A uses a crane to remove an engine from its compartment. Technician B uses an engine cradle to remove an engine from its compartment. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 4. While removing a cylinder head: Technician A keeps all rocker arms and pushrods in order. Technician B loosens each head bolt, starting with the center bolts and moving toward the ends. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 5. While discussing abrasive cleaners: Technician A says that shot is angular in shape and is used for aggressive cleaning. Technician B says that grit is an angular-shaped media and is used to peen metal surfaces. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 6. Technician A labels or marks all electrical wires before disconnecting them. Technician B labels or marks all vacuum hoses and verifies the connections to the underhood decal before disconnecting them. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 7. While discussing cleaning engine parts: Technician A says that the cleaning method used depends on the component to be cleaned and the type of cleaning equipment available. Technician B says that sometimes it’s best to clean parts by hand with soap and warm water. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 8. While loosening the axle shaft hub nuts on a FWD vehicle: Technician A says that a large breaker bar should be used to prevent damage to the bearings. Technician B says that these nuts should be loosened with the vehicle on the floor and the brakes applied. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 9. While preparing to remove an engine: Technician A disconnects the refrigerant lines at the air-conditioning compressor and allows the refrigerant to totally leak out before removing the compressor. Technician B installs plugs in the ends of the refrigerant hoses after they have been disconnected. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B 10. After removing the vehicle's hood in preparation for removing the engine: Technician A places the hood on the roof of the vehicle. Technician B sets the hood aside in a safe place on fender covers or cardboard. Who is correct? a. Technician A c. Both A and B b. Technician B d. Neither A nor B Next: Lower End Theory and Service Prev.: Crack Detection Home Article Index top of page |
