OBJECTIVES

2. OBJECTIVES After studying Chapter 17, the reader should be able to: • Understand the cooling system’s role in maintaining proper engine temperature. • Realize the effects that overcooling and overheating have on an engine. • Understand what the parts of the cooling system do and how they operate. • Understand what coolant is and what can happen if it is not properly maintained.

3. INTRODUCTION • Automotive engines use a cooling system to remove excess combustion heat. • Modern cooling systems are designed to maintain an even temperature of about 180 to 230°F (82 to 113°C); this is at or above the boiling point of water. • A coolant mixture of water and antifreeze is used, and, because it is under pressure, the coolant has a still-higher boiling point.

4. FIGURE 17-1 Most cooling systems contain these components. (Courtesy of Gates Corporation) INTRODUCTION

5. WATER JACKETS • When an engine cylinder block and head are cast, cavities called water jackets are formed around the cylinder walls and combustion chambers. • These water jackets allow coolant to circulate around the very hot areas, including the exhaust valve seats, as well as the relatively cooler areas of the lower cylinders. • The coolant absorbs heat from the hot areas and transfers this heat to the colder areas in the engine or radiator

6. FIGURE 17-2 Water jackets are chambers that surround the cylinders and head of the combustion chamber. WATER JACKETS

7. FIGURE 17-3 A cylinder block (a) is cast in a mold in which sand cores form the cylinders and water jackets (b). Molten cast iron fills the voids in the mold to form the outside of the block and the cylinder walls. (a courtesy of Ashland Chemical) WATER JACKETS

8. THERMOSTAT • The thermostat is a temperature-controlled coolant valve. • In most engines, it is located at the upper radiator hose connector, which forms the thermostat housing. • In a few engines the thermostat is located at the lower radiator hose or inlet connection.

9. FIGURE 17-4 Most thermostats (2) are mounted in the coolant outlet. A cap-mounted thermostat is shown at left. (Reprinted with permission of General Motors Corporation) THERMOSTAT

10. FIGURE 17-5 In most engines, a bypass hose allows coolant to circulate back to the water pump when the thermostat is closed.(Courtesy of Chrysler LLC) THERMOSTAT

11. FIGURE 17-6 Some systems use a three-way thermostat that closes off the bypass when the thermostat opens. THERMOSTAT

12. FIGURE 17-7 When the heat motor of the thermostat reaches the correct temperature, it pushes the piston outward and opens the thermostat. (Courtesy of Stant Manufacturing) THERMOSTAT

13. FIGURE 17-8 An inlet thermostat is normally located where the lower radiator hose attaches to the engine. THERMOSTAT

14. FIGURE 17-9 Most engines use a thermostat located at the engine coolant outlet (a); a few place the thermostat at the coolant inlet (b). THERMOSTAT

15. FIGURE 17-10 In most vehicles, the water pump is driven by the accessory drive belt. (Courtesy of Chrysler LLC) WATER PUMP • In most vehicles, the water pump is driven by the accessory drive belt, commonly called the drive belt or fan belt, at the front of the engine.

16. FIGURE 17-11 Coolant enters the water pump at the center of the impeller. From here, the impeller spins the coolant, and centrifugal force sends it through the outlet to the water jackets. WATER PUMP

17. FIGURE 17-12 In most engines, the coolant flows into the block’s water jackets, upward to the head(s), and out the passages at the front or rear of the head. The amount of flow is controlled by the holes in the head gasket. WATER PUMP

18. FIGURE 17-13 This cutaway view of a water pump shows the relationship of the shaft, bearing, seal, and impeller. A weep hole (not shown) allows any coolant that leaks past the seal to drain. (Courtesy of Gates Corporation) WATER PUMP

19. FIGURE 17-14 A V (a) and a V-ribbed belt (b). The V-ribbed belt has smaller V sections. (Courtesy of Veyance Technologies, Inc.) WATER PUMP • Drive Belt • In the past, most vehicles used one or more V belts to drive the water pump and other accessories. • Many modern vehicles use a single, wide, serpentine V-ribbed belt.

20. FIGURE 17-15 A V belt is made from different compounds, each having a special purpose. (Courtesy of Veyance Technologies, Inc.) WATER PUMP

21. FIGURE 17-16 The tension of most V belts is adjusted by pivoting the driven component. (Courtesy of Chrysler LLC) WATER PUMP

22. FIGURE 17-17 A cutaway view of a V-ribbed belt showing its internal construction (a). (b) shows a typical belt routing and demonstrates why this belt is called a serpentine belt. Note that the water pump rotates in an opposite direction because it is driven by the back of the belt. (Courtesy of Veyance Technologies, Inc.) WATER PUMP

23. FIGURE 17-18 This idler pulley includes an automatic tensioner (a). An exploded view is shown in (b).(b Courtesy of Gates Corporation) WATER PUMP

24. FIGURE 17-19 When a V belt is used, all the driven components rotate in a clockwise direction. With a serpentine belt, those components driven by the back of the belt rotate counterclockwise. WATER PUMP

25. RADIATOR • The radiator is a heat exchanger that gets rid of excess engine heat. • Most radiators are of fin-and-tube design. • Coolant flows through tubes from the inlet tank to the outlet tank. • The fins are attached to the tubes to provide the air contact area. • The fin-and-tube area is commonly called the core.

26. FIGURE 17-20 A radiator core is made up of tubes and fins (a) that join to a header and tank (b). (Courtesy of Modine Manufacturing) RADIATOR

27. FIGURE 17-21 Most older vehicles use a downflow radiator design (a) in which the coolant flows downward. Most newer vehicles use a crossflow design (b) in which the coolant flows across the radiator. (Courtesy of Modine Manufacturing) RADIATOR

28. FIGURE 17-22 Most older radiators used a brass or copper core with the tanks soldered in place (a). Many newer radiators use an aluminum or brass core with plastic tanks (b). (Courtesy of Modine Manufacturing) RADIATOR

29. FIGURE 17-23 The pressure cap can be located on the coolant recovery reservoir (a) or the upper radiator hose (b). RADIATOR

30. RADIATOR • Pressure Cap • The pressure cap seals the cooling system so it will hold pressure. • Pressure is used to raise the coolant boiling point so the engine can operate at a higher, more efficient temperature. • A spring in the cap pushes the cap’s lower gasket against a seat in the filler neck to form a seal.

31. FIGURE 17-24 A pressure cap (a) and a radiator filler neck (b). As the cap is installed, the cam portion pulls the cap downward to seat the lower sealing gasket firmly on the sealing seat (c). (a and b courtesy of Stant Manufacturing) RADIATOR

32. FIGURE 17-25 The boiling point of water increases with pressure and the addition of antifreeze. RADIATOR

33. FIGURE 17-26 Do not remove the cap from a hot system unless absolutely necessary. If you have to remove it, follow these precautions. Release of cooling system pressure can produce instant and severe boiling. RADIATOR

34. FIGURE 17-27 The cap’s pressure valve is opened when coolant pressure is greater than the pressure spring (right). This weighted vacuum valve opens from gravity when coolant pressure drops (left). Some caps use a small spring that holds the vacuum valve closed (not shown). RADIATOR

35. FIGURE 17-28 When the cap relieves pressure, coolant travels through the transfer tube to the reservoir. The coolant returns to the radiator during cool-down. RADIATOR

36. RADIATOR • Coolant Recovery Reservoir • In older vehicles, a certain volume of air was kept in the radiator to allow for expansion. • Air adds oxygen to the system; this leads to oxidation and corrosion. • Air also mixes with coolant as it passes through the radiator, which reduces efficiency. • An air or steam pocket in a water jacket can allow the temperature of some portions to reach critical points.

37. RADIATOR • Cooling Modules • Modern vehicles require more than one system to be air cooled; these systems can include the cooling system, A/C system, automatic transmission fluid, engine oil, power steering fluid, and incoming air charge from a supercharger.

38. FIGURE 17-29 This A/C condenser is attached to the radiator to form a cooling module. Some modules include an oil cooler for power steering or engine oil. (Courtesy of Visteon) RADIATOR

39. FIGURE 17-30 Air enters the radiator from the grill area above or below the front bumper. It exits through the engine compartment to the front wheel wells and below the vehicle. (Reprinted with permission of General Motors Corporation) FAN • The fan ensures adequate air flow through the radiator while the vehicle is stopped or moving at low speeds. • At cruising speeds, the fan is not needed because ram air through the grill supplies ample air.

40. FIGURE 17-31 Most RWD vehicles drive the fan through a clutch that is mounted on the water-pump shaft (a). Most FWD vehicles use an electric fan (b). (b. Courtesy of Chrysler LLC) FAN

41. FIGURE 17-32 Use caution around a running engine. Things can get caught in the fan or belts, or a fan blade can break off and fly outward with great force. An electric fan can start up at any time on many vehicles. (Courtesy of Everco Industries) FAN

42. FAN • Fan Clutch • Most fan clutches are temperature-controlled fluid couplings and are called thermal or thermostatic fan clutches. • They are designed to slip when cold and can only drive the fan to certain speeds when hot. • There is also a nonthermal design that can only drive the fan up to a speed of about 1,200 to 2,200 rpm. • A fan clutch improves fuel mileage because it reduces the fan’s horsepower draw, and it also greatly reduces the noise level. • When a fan clutch is engaged, the increased air flow and noise level from cold to hot are quite noticeable

43. FIGURE 17-33 The horsepower draw of a solid-drive fan increases significantly as engine speed increases. With the clutch disengaged, draw is limited to about 2 horsepower (hp). With the clutch engaged, draw is limited to about 18 hp. FAN

44. FIGURE 17-34 A nonthermal fan (a) merely slips as speed increases; a thermal fan (b) disengages almost completely when it is cool. (Courtesy of Stant Manufacturing) FAN

45. FAN • Electric Fans • The fan blade is attached directly to the shaft of the electric motor; the motor mounting bracket often includes the shroud for the fan. • Fan motors and fans of different sizes are used by vehicle manufacturers and are used as single units or in pairs. • They can also be mounted as pusher fans in front of the radiator or puller fans behind it. • Larger fans and fans with more blades can move more air, but they are noisier and require larger motors, which in turn require more electrical current

46. FIGURE 17-35 This vehicle uses two electric fans (arrows) mounted in a fan shroud that helps improve the air flow. FAN

47. FIGURE 17-36 These two fan motors are controlled by two relays that are switched on and off by the PCM. FAN

48. FIGURE 17-37 This pickup uses an electric fan, a mechanical fan, and a fan clutch. TECH TIP • Some vehicles use a combination of a mechanical fan with fan clutch and an electric fan

49. FIGURE 17-38 This cooling fan is driven by hydraulic pressure from the power steering pump. The hydraulic fluid flow is controlled by an electric solenoid that is controlled by an electronic module. FAN • Hydraulic Cooling Fan • Some modern vehicles use a cooling fan that is driven by hydraulic pressure from the power steering system

50. HOSES • Two large hoses connect the engine’s water jackets to the radiator. • The upper hose transfers hot coolant to the radiator; the lower hose returns the coolant, which is now cooler, to the engine. • These hoses must be flexible to allow the engine to move on the motor mounts. • Hose flexibility also removes the need for close alignment of the connections between the radiator and engine. • Hose flexibility also removes engine vibrations, which can shake a radiator apart.