The instructional design of this textbook includes student-focused learning tools to help you succeed. This visual guide highlights these features. Chapter Opening Materials Each chapter opening contains a list of learning objectives and a list of technical terms. Objectives clearly identify the knowledge and skills to be gained when the chapter is completed. Technical Terms list the key words to be learned in the chapter. Additional Features Additional features are used throughout the body of each chapter to further learning and knowledge. Warnings alert you to potentially dangerous materials and practices. Cautions alert you to practices that could potentially damage equipment or instruments. Notes provide advice and guidance that is especially applicable for on-the-job situations. Features of the Textbook 61 Copyright Goodheart-Willcox Co., Inc. After studying this chapter, you will be able to: • Explain the operating principles and interaction of the major diesel engine components, such as the cylinder block, cylinder head, valve train, and accessory items. • Explain the difference between two-stroke cycle and four-stroke cycle diesel engines and describe what happens during each piston stroke in both types. • Explain the basics of both two-cycle and four- cycle valve timing. • Define the most popular diesel engine configurations. • Name the two types of combustion chamber designs. • Explain the difference between direct and indirect fuel injection. • List the functions of the fuel injection system and name the five types of fuel injection systems used in modern diesel engines. • Explain the basic engine performance terms and formulas, such as bore, stroke, compression ratio, volumetric efficiency, horsepower, and torque. Principles of Engine Operation Technical Terms after bottom dead center (ABDC) air box atmospheric pressure before bottom dead center (BBDC) after top dead center (ATDC) before top dead center (BTDC) bore bottom dead center (BDC) brake horsepower (bhp) cam followers camshaft charge air cooler clearance volume companion cylinders compression ratio compression stroke connecting rod connecting rod journalss crankcase crankshaft crosshead cylinder block cylinder displacement cylinder headcoolant cylinder liners direct injection combustion chamber distributor pump systems double-acting piston engine engine displacement exhaust manifold exhaust ports exhaust stroke exhaust valves fl ex plate fl ywheel fl ywheel housing four-stroke cycle engine fuel injection system governor head gasket head group horizontally-opposed engine horsepower indicated horsepower (ihp) individual pump system inline engines intake manifold intake ports intake stroke intake valves internal engine balancer journals main bearing journals mean effective pressure (MEP) mechanical effi ciency multiple-plunger, inline system oil oil oil tube oil pistonno piston pinn piston power strokerst precombustion chamber pressuresures pressure-time injection (PT system) push push rated Chapter 4 y g s c ting d j l k mechanic multiple- ggalleriesilla ppann ppickup ic u ssealsls on on rirings er comb ssure- h rorods h tutubes hhorsepowerro in e perf e mul ppump ssystem ed Chapter 11 Cooling Systems 239 Copyright Goodheart-Willcox Inc.. hoses as the coolant cools and contracts, Figure 11-13B. In addition, if the vehicle is equipped with a recovery system, the vent will also allow the liquid from the overflow tank to return to the radiator. This refills the system and normalizes the pressure. All radiator caps are designed to meet SAE standards for safety. These standards require that all caps have a detent position, which allows pressure to escape from the cooling system without allowing the hot coolant to escape. Warning: Escaping steam and water can cause scalding and extreme burns. A radiator cap should never be removed when it is hot. Wait until the cap is cool enough to hold with your bare hand before releasing pressure and removing. A lever or button may be found on the cap to release the pressure prior to removing the cap. Only after all pres- sure has been released should any attempt be made to remove the cap from the filler neck. Radiators and caps can be tested with a relatively simple, inexpensive tester. This tester consists of an air pump, a pressure gauge, and a filler neck adapter, Figure 11-14. The cap is placed on the tester’s filler neck and air pressure is applied with the pump. The gauge will indicate the “pop-off” pressure of the cap. This reading should correspond with the pressure specifications shown on the face of the cap. Figure 11-15 shows how the pres- sure tester is used to check the cooling system for leaks. Hot air permitted to pass around the sides or bottom of the radiator and then drawn through the unit again will cause engine overheating. Radiator Pressure Caps At one time, a radiator cap was simply designed to keep liquid coolant from splashing out of the radiator. Today’s radi- ator caps are equipped with pressure springs and atmospheric vents. This pressure control valve/cap is normally a closed valve. The cap is designed to permit a pressure in the cooling system equal to the rate stamped on the top of the cap. A cap with a “9” on the top allows the cooling system to develop 9 psi (62 kPa pressure) before the valve opens, Figure 11-13A. This system pressure raises the boiling point of the coolant and reduces coolant loss. The maximum allowable coolant tem- perature, regardless of the pressure cap used, is 210°F (99°C). When pressure in the system exceeds the specified limits, the seal between the cap and the radiator filler neck opens, allowing the coolant to vent into the recovery (surge) tank. Note: every 1 psi of pressure increase in the cooling system, the boiling point is raised 3°F. An atmospheric vent or valve in the cap ensures that atmospheric pressure will not collapse the radiator and Adapterterp 11-15. Applying pressure with a tester to cooling system for leaks. Manufacturing, Inc.)) Figure 11-14. Radiator pressure tester. (Stant Manufacturing, Inc.) Coolant Valve opened by pressure Valve by vacuum A B Coolant Figure 11-13. Operation of a typical pressure radiator cap. A—Pressure valve open. B—Vacuum valve Diesel Corp.) c CCo., A FFigure i Applying w th ccheckk h tthee ((Stant S Va ve oopened y m ration op oopen.(Detroitit pen.(Detro 148 Diesel Engine Technology Copyright Goodheart-Willcox Co., Inc. Note: The crankshaft must rotate freely when installation is completed. XX XX XXXX Connecting the Piston Assembly to the Crankshaft The piston assembly is in the as follows: 1. Make sure that the cylinder liner is clean. Then, apply a coat of clean lubricating oil to the piston rings, the inside diameter (ID) of the cylinder liner, and the ID of the ring compressor tool. 2. Double-check that the piston rings are properly indexed and their gaps are in the correct positions. Slip a ring compressor over the piston rings as shown in Figure 7-45. Caution: If using a strap-type ring compressor, such as the type shown in Figure 7-46, make sure the inside end of the strap does not hook on a ring gap and break the ring. 3. Turn the engine to the vertical or side position and rotate the crankshaft so any two crank throws are at bottom center, Figure 7-47. 4. Position the rod so the numbered side is toward the correct side of the engine. Check the service manual for exact positions. Push the piston through the ring compressor until all the rings are inside the liner, Figure 7-48. Use a firm, steady pressure. If binding occurs, remove the assembly and make the necessary corrections. Binding generally indicates an incorrectly aligned ring. Never force a piston into a liner. Finally, working from the bottom of the block, pull the rod to within 1” (25.4 mm) of the rod journal. Caution: Use extreme care when installing the piston and rod assembly to avoid bending the piston cooling tube (if so equipped) or damaging the connecting rod bearing and/or crank journal. If there are studs in the connecting rod, put something over the threads to prevent scratching the crank journal. 5. Coat the bearing shell face with clean engine oil. Do not lubricate the steel back or ends of the shell. Install the bearing shell into the rod bore with the locking tang seated properly and the oil hole in the shell indexed with the oil gallery in the connecting rod, Figure 7-49. Pull the rod down against the journal carefully so that the bearing shell is not dislodged or Figure 7-46. Strap-type ring compressors are used by many technicians. Take care when installing this type of compressor. Figure 7-47. Turn the crankshaft to align the rod journals for piston installation. The crankshaft should turn with no binding. (Cummins) Figure 7-45. Ring compressors come in many sizes. When installing the compressor, make sure the rings are properly positioned. This step is critical, so do not hurry. (Mack Trucks, Inc.)