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CHAPTER 18Cooling System Inspection, Trouble,

Diagnosis, and Service

Automotive Heating and Air Conditioning, 6/eBy Thomas S. Birch

Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson EducationUpper Saddle River, NJ 07458 • All rights reserved.3

After studying Chapter 18, the reader will be able to:

1. Perform the preventive maintenance operations and adjustments necessary to keep a cooling system operating properly.

2. Inspect a cooling system to determine whether it is operating correctly.

3. Perform the standard cooling system tests to locate the cause of a problem.

4. R&R a faulty cooling system component. 5. Complete the engine cooling system diagnosis

and repair operations in the ASE Task List, Section C (see Appendix A ).

OBJECTIVES



KEY TERMS

• Air lock • Angular misalignment • Backflush • Chemical flush • Coolant voltage • Finger check • Flush • Hydrometer• Mechanical reverse flush

• Parallel misalignment • pH balance • Pressure test • Refractometer • Reserve alkalinity (RA) • Test strip



INTRODUCTION

• Engine cooling systems require periodic maintenance to keep them operating properly. • These checks range from checking coolant level

and condition, to inspecting belts and hoses, to replacing coolant.



PREVENTIVE MAINTENANCE OPERATIONS

• Preventive maintenance operations are usually listed in the vehicle owner’s manual and in the maintenance and lubrication section of the service manual (along with the maintenance schedule). • These schedules usually call for regular inspection

of the coolant level (some recommend this at each gasoline refill), annual inspection of the belts and hoses, and a change of the coolant at the recommended intervals.



PREVENTIVE MAINTENANCE OPERATIONS

• COOLANT LEVEL• COOLANT MIXTURES• COOLANT CONDITION• CHANGING COOLANT• AIR LOCKS• DRIVE BELT INSPECTION AND REPLACEMENT• HOSE INSPECTION AND REPLACEMENT



TECH TIP

1. A simple finger check (rubbing a finger around the inside of the filler neck) provides the technician with a quick way to check for faulty coolant and a dirty system.

2. Many technicians will lower the coolant level to expose some of the radiator tubes. This allows a limited visual inspection of the radiator tubes for scale and other problems.

3. A brown, muddy sludge has been found in systems using Dexcool, an extended-life antifreeze. The cause of this sludge has been attributed to incomplete bleeding that left air in the system.



TECH TIP

1. Some technicians have experienced breakage problems with plastic drain valves. They feel that disconnecting the lower radiator hose from the radiator hose is almost as fast as opening a drain valve and saves the problem of trying to find a replacement valve.

2. If a plastic drain valve that is threaded into a radiator tank breaks off, it can be removed using an old file. Heat the tang of the file, and push it into the center of the broken plastic. It should melt its way into the plastic. Let it cool for a few minutes, and then unscrew the broken part.



TECH TIP

1. A special spill-free funnel with adapters that connect to most filler necks makes a leakproof connection to the filler. This funnel can then be filled with coolant. This allows the technician to leave and return later, after the air pockets move to the funnel and the voids fill with coolant.

2. Air lock problems can be reduced by partially filling some of the components with coolant as they are replaced or blocking the thermostat open, as described in a following section.

3. An air lock can also be removed by connecting a hand vacuum pump to the CRR connection at the radiator filler neck. Operating the vacuum pump to reduce cooling system pressure will often pull pockets of air from the system.



• Lisle 22150 Coolant funnel• http://www.youtube.com/watch?v=JlJJq6n9XxI&feat

ure=related



TECH TIP

1. In the late 1990s, auto manufacturers began replacing belts made with neoprene and began using EPDM ( ethylene propylene diene monomer ) belts. The neoprene material cracks and chunks fall out as the belt begins failing. EPDM belts last much longer and simply wear out.

2. EPDM belt wear can be checked using a special gauge.



TECH TIP

• If a belt shows signs of failing early, check for parallel or angular misalignment. Either of these conditions can cause excessive belt temperature and shortened life. Pulley and sheave alignment is checked by sighting along the pulleys or placing a straightedge or round bar along the pulleys.



• EDPM Belt• http://www.youtube.com/watch?v=OrpbfqV8hzE



TECH TIP

1. Squeeze the hose near the connectors and compare the feel with the center. Electrochemical degradation usually occurs within 2 inches of the ends of a hose, and soft spots, gaps, or channels indicate a weak hose.

2. The hose is usually stuck in place; to prevent damage to the connector, many technicians slice the end of the hose with a sharp knife. Then the hose end can be peeled loose.



TROUBLE DIAGNOSIS

• COOLING SYSTEM INSPECTION• PRESSURE TESTS• COMBUSTION LEAK CHECKS• THERMOSTAT CHECK• FAN CLUTCH TEST• ELECTRIC FAN TESTS• WATER-PUMP TEST



TECH TIP

• A screw-type clamp should be tightened to 30 to 40 in.-lb of torque (the point where the hose rubber squeezes into the slots of the clamp).



TECH TIP

1. On vehicles with two-speed electric fans, try to produce high-speed fan operation to ensure that it will work properly when it becomes needed.

2. Infrared thermometers make temperature checks much easier; merely point the unit at the heat source to be checked. The temperature is then read on the unit’s display.



COOLING SYSTEM SERVICE AND REPAIR

• FLUSHING A SYSTEM• COMPONENT REPLACEMENT

• R&R FAN AND FAN CLUTCH• R&R RADIATOR• R&R THERMOSTAT• R&R WATER PUMP



TECH TIP

• If a cup plug is in a hard-to-reach location, the old plug can be cleaned and left in place with an expandable rubber plug inserted into it.



TECH TIP

1. If replacing a fan or fan clutch, pay attention to the direction of rotation. Most modern engines that use a serpentine, V-ribbed belt drive the water pump and fan off the flat, back side of the belt so it turns in a counterclockwise direction. Engines that use a plain V belt drive the fan and water pump from the inside of the belt, and the fan turns in a clockwise direction. Both the fan and fan clutch must match the direction of rotation.

2. Some fan clutches thread onto the drive shaft from the water pump. They are removed by unscrewing them in a direction opposite to normal rotation. On some vehicles, a special wrench is required for this operation.



TECH TIP

1. A thermostat must always be installed so that the heat motor or sensing portion is toward the hot water. A close inspection of their mountings shows that most thermostats fit into a recess. The gasket not only seals the cover but also prevents coolant flow past the thermostat. Some thermostats must be aligned as they are installed into their housing.

2. Many thermostats have an air bleed hole or notch in them. On some, the bleed hole has a jiggle pin in it to keep it open. On vertically mounted thermostats, the air bleed should be positioned in the uppermost position to bleed as much air as possible.



TECH TIP

1. When replacing a thermostat, some technicians force the valve open and place an aspirin tablet in the valve to keep it from closing completely. The partially open valve allows the air from the water jackets to escape so the coolant can enter quickly. The tablet will dissolve shortly after the system is filled.

2. Vertically mounted thermostats can be difficult to hold in position while the cover is replaced. A tip is to loop a rubber band through the thermostat and then slip it out after the cover is in place. Gaskets with an adhesive coating that will stick onto the housing can also be used to hold the thermostat in the correct position.



TECH TIP

1. Experienced technicians will recommend replacement of the fan clutch whenever a water pump is replaced.

2. Some engines use a reverse-rotation water pump that is driven by the back side of the drive belt. Standard and reverse-rotation water pumps cannot be interchanged.



SUMMARY

1. Proper maintenance prevents many cooling system problems.

2. The system should stay filled with clean coolant, which is usually a 50–50 mix of pure water and the proper antifreeze.

3. Coolant can be tested using a refractometer, hydrometer, test strips, a voltmeter, and special testers.

4. When a cooling system is filled, all the air in the system must be removed.

5. Accessory drive belts and hoses should be inspected on a regular basis and replaced when necessary.



SUMMARY

6. At the completion of every cooling system service, you should recheck the tension of the hose clamps and recheck the coolant level in the CRR and radiator.

7. A thorough inspection can locate the cause of most cooling system problems, including leaks, overheating, and overcooling.

8. Cooling system tests include system pressure, cap pressure, combustion leak, thermostat, and fan/fan clutch tests.

9. Faulty cooling system components are removed and replaced.



REVIEW QUESTIONS

1. The coolant level in a modern vehicle should be at the ______________ ______________ on the CRR, and if the radiator cap is removed, it should be even with the sealing surface in the ______________ ______________ .

2. If removing the radiator cap from a hot cooling system, be very careful because the ______________ might suddenly ______________ .

3. Dirty coolant indicates that the coolant should be ______________ and probably that the cooling system should be ______________ .

4. Coolant freeze protection can be checked using a(n) ______________, ______________ , or ______________ ______________ .

5. The most accurate checking method is the ______________ .6. A reading of more than 0.3 V at the radiator filler neck indicates a

potential problem of ______________ .



REVIEW QUESTIONS

7. The normal coolant is ______________ antifreeze and ______________ water; in very cold climates, the percentage of antifreeze can be increased to ______________ .

8. Used antifreeze should be ______________ or disposed of in the ______________ ______________ .

9. Early drive belt failure can be caused by ______________ or improper ______________ .

10. When a hose is replaced, the ______________ should be positioned right next to the connector bead, and it is a good practice to recheck clamp ______________ after the engine has been warmed up and cooled down.

11. A radiator cap is tested using a(n) ______________ ______________ .

12. Bubbles coming up through the coolant in a radiator is a sign of a(n) ______________ ______________ .



CHAPTER QUIZ

1. In a modern cooling system, the coolant level is checked at the

a. radiator.

b. thermostat cover.

c. coolant recovery reservoir.

d. None of these



CHAPTER QUIZ

2. While discussing coolant changes, Technician A says that the old coolant can simply be poured down the drain. Technician B says that used coolant must be recycled. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

3. Two Technicians are discussing coolant flow. Technician A says that you should not be able to feel a coolant flow through the upper radiator hose while the engine is cold. Technician B says that when the thermostat opens, the upper hose should start getting hot and you should feel a flow through it. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

4. Technician A says that a cooling system should hold pressure for at least 2 minutes when its pressure is checked. Technician B says that the pressure tester can also be used to check for combustion leaks. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

5. A thermostat that is stuck open causes the engine to overheat.

a. True

b. False



CHAPTER QUIZ

6. Technician A says that a leaky heater core may show up as a drip onto the carpet. Technician B says that you can test a heater core for leaks using a pressure tester. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

7. Technician A says that fan clutch operation can be tested using a strobe light. Technician B says that the fan clutch should be locked up when the engine is cold. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

8. Two Technicians are discussing system flushing. Technician A says that you should flush a system in the direction of normal coolant flow. Technician B says that a system should be flushed until clean water flows out of the system. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

9. Technician A says that if a core plug is leaking and is in a difficult location, an expandable rubber plug can be inserted into it. Technician B says that rubber plugs should always be installed dry. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

10.Two Technicians are discussing radiator removal. Technician A says that you should use two wrenches as you loosen the cooler lines to the automatic transmission. Technician B says that cooler lines on modern vehicles might require special tools to disconnect the quick- connect-type coupler system. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

11.Technician A says that the major cause of engine overheating is a faulty thermostat that opens at a too-high temperature. Technician B says that the bleed notch or jiggle pin should be at the top when installing vertically mounted thermostats. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

12.Technician A says that after service, it is good practice to retighten hose clamps after the engine has been run and then cooled down. Technician B says that when coolant is replaced, the coolant level should be checked after the engine has been warmed up. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

13.Two Technicians are discussing antifreeze. Technician A says that green antifreeze should be changed every year or two to keep a cooling system clean. Technician B says that an overheating system can be kept from boiling by using straight antifreeze for a coolant. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B



CHAPTER QUIZ

14.Technician A says that the fan used with modern RWD vehicles always rotates in a clockwise direction, the same as the crankshaft. Technician B says that the fan clutch used on FWD vehicles can cause fan rotation in either direction. Who is correct?

a. A only

b. B only

c. Both A and B

d. Neither A nor B

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