Perform Under chassis Preventive Maintenance

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Notes Format of Learner’s Guide

Course: Automotive Servicing NCII
Unit of competency: Perform Under chassis Preventive Maintenance

Module: At the end of the session, learners should be able to:
Learning outcomes:

1. Check clutch fluid and lines
2. Inspect brake system

3. Inspect/Replace power steering fluid
4. Inspect/change transmission/ differential fluid
5. Check tires and tire pressures
6. Check under-chassis body bolts and nuts

Duration: 40 Hrs
Situating Learning: A newly purchased LAND CRUISER vehicle from TOYOTA

PHILIPPINES, INC., will have its 10,000 km periodic check-up as part of
company warranty. You work as an under chassis technician in their service
department. You are assigned to perform preventive maintenance of under
chassis component parts. The workshop supervisor reminds you that all
necessary supplies and materials of that specific model are already
available in the supply office. The activity will be done in the company
service bay station.

The vehicle shall undergo intensive inspection and replenish necessary
supplies and materials pertaining to the prevention of troubles particularly
under chassis systems. You shall also conform with the specifications in the
service manual

Assessment Criteria: Assessment requires evidence that the candidate must:

 Checked/Inspected clutch/brake fluid and lines

 Inspected/changed transmission/ differential fluids
 Inspected/Replaced power steering fluid
 Checked/Re-filled automatic transmission fluid
 Checked tires and tire pressures
 Checked under-chassis body bolts and nuts

Pedagogical Training in Instructional Design & Delivery for TVET Page 1
© 2010, Institute of Technical Education, Singapore

DLM 03 Developing print-based Learner’s Guide including all related documents
Notes Format of Learner’s Guide

Learning chunk Performance Criteria Learning Activities Learning documents
1: Check Clutch Fluid (Brief description of
and Lines Clutch fluid level is strategies, sequence (Documents
checked and of lesson, evaluation)
2.Inspect Brake maintained between 1.1Check clutch fluid referenced by each
System minimum and and lines
maximum. learning activity)
1.1.2
Clutch lines are Read information
checked for twist and 2.1 Inspect Brake sheet
bends. System 1.1.1- Components and
2.2 Identify types of functions of clutch system
Clutch cover must be brakes Answer worksheet
fitted in the cap. questions 1.1.2
Read Information
Clutch fluid is used. sheet
1.1.3Classification and
Brake fluid level is types of fluids
checked and Answer worksheet
maintained between questions
the minimum and Read procedures in
maximum, and clear, checking fluids and
undiluted fluid is used. lines
1.1.1 Perform
Brake lines or hoses operation sheet.
are checked and freed Read Information
of twist and bends. sheet
2.1.1- Components
Brake pedal free play and function of brake
specified. system components

2.3 Characteristics of
tubes/pipes and hoses

2.4 Brake pedal
adjustment
2.5 Define components
parts of brake system.

Brakes operation is
checked and tested.

Hydraulic fluid
used/changed without
spillage and at the level
specified.

Brake pedal/height
/pre-play checked and
adjusted

Bleed hydraulic brake.

Emergency brake
functions is checked.

Points of adjustment of
emergency brake is
identified.

Pedagogical Training in Instructional Design & Delivery for TVET Page 2
© 2010, Institute of Technical Education, Singapore

DLM 03 Developing print-based Learner’s Guide including all related documents
Notes Format of Learner’s Guide

Learning chunk Performance Criteria Learning Activities Learning documents
(Brief description of (Documents
3.Inspect/Replace 3.1 Power steering strategies, sequence
Power Steering Fluid linkages and of lesson, evaluation) referenced by each
connections inspected
3.2 Vehicle is parked 3.1 Inspect/ Replace learning activity)
and engine running at Power Steering Fluid
idle speed Read Information
3.3Fluid is 3.2 Classification of sheet
inspected/replaced fluids 3.1.1 – Basic Types of
3.3 Identify power Power Steering
steering linkages and Systems
connections and Answer Worksheet
operations Questions 3.1.2

Read Information
Sheet
3.1.3 – Replacement
procedures of
gear/ATF
Perform Job Sheet

4.Inspect/Change Gear oil is inspected. 4.1 Inspect/Change Read Information
Transmission/Differen transmission/Differential Sheet
tial Fluid The vehicle is position. fluid 4.1.1 – Classification
4.2 Classify gear and and viscosity range
Transmission gear oil is ATF data of fluids
selected and oil used is Answer Worksheet
clear and not diluted Questions 4.1.2
with other substances.
Read Information
Grade/Classification sheet
4.1.3 – Characteristics
and level of gear oil of gear oil and ATF
used must be in Answer Worksheet
questions 4.1.4
accordance with
manufacturer’s Read Information
Sheet
specification 4.1.5 – Checking and
replacement of
Lubricants
Answer Job Sheet
questions 4

5.Check Tires and Tire Tire is inspected for 5.1Check Tires and Tire Read Information
Pressure Sheet
Pressure damage or deformities 5.1.1 - Types of tire
purpose and
and free of solid object. construction
Answer Worksheet
Tire pressure is Questions 5.1.2
checked and
maintained.

Tire rotation is Read Information
performed. Sheet
5.1.2 – Tire Ratings
and designations
Answer Worksheet

questions 5.1.3

Read Information
Sheet

Pedagogical Training in Instructional Design & Delivery for TVET Page 3
© 2010, Institute of Technical Education, Singapore

DLM 03 Developing print-based Learner’s Guide including all related documents
Notes Format of Learner’s Guide

Learning chunk Performance Criteria Learning Activities Learning documents
(Brief description of (Documents
6.Check Under strategies, sequence
chassis Body Bolts of lesson, evaluation) referenced by each
and Nuts learning activity)
Bolts/nuts including tire 6.1 Check Under
5.1.4 – Tire Care
studs bolts/nuts are chassis Body Bolts and Read Information
Sheet
checked Nuts 6.1.1- Types of bolts
and fasteners
Body bolts/nuts torque Answer Worksheet
is checked and questions 6.1.2
maintained.
Read Information
Checking procedure sheet
6.1.3 –Fastener
according to Torque
manufacturer’s Answer Worksheet
questions 6.1.4
specifications.
Read Information
Tightness of the bolts is sheet
determined by the 6.1.5 – Using a pitch
sound produced by gauge for theaded
tapping lightly fasteners
bolts/nuts with pointed Answer Operation
hammer. Sheet Questions 6.1.6

Read Information

sheet
6.1.7 – Hardness and

strength of bolts
Answer Job sheet

Questions 6.1.8

Pedagogical Training in Instructional Design & Delivery for TVET Page 4
© 2010, Institute of Technical Education, Singapore

Information Sheet 1.1.1: Components and Fluid Maintenance of Clutch System

Learning outcomes:
1 Check Fluid and Lines
Learning Activity:
1.1.1 Components and Fluid Maintenance of Clutch System

CLUTCH
The clutch is used on vehicles with manual transmission/transaxles. It is used to

mechanically connect the engine’s flywheel to the transmission/transaxle input shaft (Figure 1).
It does this through the use of special friction plate (clutch plate) that is splined to the input
shaft. When the clutch is engaged, the clutch disc contacts the flywheel, transferring power
through the clutch plate to the input shaft.

Figure 1

CLUTCH MAINTENANCE

All clutches required checking and adjustment of linkage at regular intervals. Vehicles
with external clutch linkage require periodic lubrication.

CLUTCH LINKAGE ADJUSTMENT

Except for systems with self-adjusting mechanisms, the release bearing should not touch the
pressure plate release levers when the clutch is engage (pedal up). Clearance between these
parts prevents premature clutch plate, pressure plate, and release bearing wear. As the clutch
disc wears and becomes thinner, this clearances changes.

Clearance can be ensured by adjusting the clutch linkage so the pedal has a specified
amount of play or free play. Free travel is the distance a clutch pedal moves when
depressed, before the clutch fork begins to move the release bearing.

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Information Sheet 1.1.1: Components and Fluid Maintenance of Clutch System

To check the pedal play, use a tape measure or ruler. Place the tape measure or ruler
beside the clutch pedal and the end against the floor of the vehicle and note the reading
(Figure 2). Then, depress the clutch pedal just enough to take up the pedal play and note the
reading again. The difference between the two readings is the amount of pedal play.

Adjustment should be performed when the pedal play is not correct or when the clutch
does not engage or disengage properly. To adjust clutch pedal play, refer to the
manufacturer’s service manual for the correct procedure and adjustment point locations. Often
pedal play can be increased or decreased by turning a threaded fastener located either under
the dash at the clutch pedal or where the linkage attaches to the clutch fork.

Clean the linkage with a shop towel and solvent, if necessary, before checking it and
replacing any damaged or missing parts or cables. Check hydraulic linkage systems for leaks
at the clutch master cylinder, hydraulic hose, and slave cylinder. Then adjust the linkage to
provide the manufacturer’s specified clutch pedal play.

Figure 2 Checking Clutch Pedal Play

EXTERNAL CLUTCH LINKAGE LUBRICATION

External clutch linkage should be lubricated at regular intervals, such as during chassis
lubrication. Refer to the vehicle’s service manual to determine the proper lubricant. Many
clutches linkages use the same chassis grease that is used for suspension parts and U-joints.
Lubricate all the sliding surfaces and pivot points in the clutch linkage (Figure 3). The linkage
should be move freely after lubrication.

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Information Sheet 1.1.1: Components and Fluid Maintenance of Clutch System
On vehicles with hydraulic clutch linkage, check the clutch master cylinder reservoir fluid level.
It should be approximately ¼ inch from the top of the reservoir. It must be refilled, used
approved brake fluid. Also, since the clutch master cylinder does not consume fluid, check the
leaks in the master cylinder, connecting flexible lines, and slave cylinder, if the fluid is low.

Figure 3 All of the clutch linkage lubrication points are marked with an arrow

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Worksheet 1.1.2. : Perform Underchassis Preventive Maintenance

Learning outcomes:
1 Check Clutch Fluid and Lines
Learning Activity:
1.1 Clutch Components and fluid line Maintenance

REVIEW QUESTIONS

1. List three types of clutch linkages used in modern vehicles.
a. ________________________________________________________________________
b. ________________________________________________________________________
c. ________________________________________________________________________

2. Is minor pulsation a normal condition in typical clutch operation?
__________________________________________________________________________

3. Technician A says a stretched clutch cable could cause gear clash during shifting. Technician B

says a leaking clutch slave cylinder could cause premature release bearing wear. Who is correct?

a. Technician A c. Both A and B

b. Technician B d. Neither A nor B

4. Why must the pressure plate retaining bolts be loosened a little at a time in a rotating pattern?
__________________________________________________________________________
__________________________________________________________________________

5. List four possible causes of clutch slippage.
a. ________________________________________________________________________
b. ________________________________________________________________________
c. ________________________________________________________________________

6. When installing a new release bearing, Technician A says the outer surface of the transmission’s

front bearing retainer should be lubricated. Technician B says the release lever and pivot should

be lubricated. Who is correct?

a. Technician A c. Both A and B

b. Technician B d. Neither A nor B

7. What safety precautions must be taken concerning dust in the bell housing?
__________________________________________________________________________
__________________________________________________________________________

8. Describe the procedure for checking clutch pedal free travel

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Worksheet 1.1.2. : Perform Underchassis Preventive Maintenance

9. While discussing the possible causes for damage to the surface of a pressure plate. Technician A

says a worn clutch disc can score the surface. Technician B says insufficient pedal free travel can

cause it to overheat. Who is correct?

a. Technician A c. Both A and B

b. Technician B d. Neither A nor B

10. List three possible causes of a noisy bearing during clutch operation.
a. ________________________________________________________________________
b. ________________________________________________________________________
c. ________________________________________________________________________

ANSWER KEY:

1. a. shaft and lever
b. cable
c. hydraulic

2. Yes
3. a
4. To prevent clutch cover distortion
5. a. Oil-soaked or worn disc facing

b. warped pressure plate
c. weak diaphragm
d. release bearing contacting and applying pressure to the release levers
6. c
7. Clutch disc dust may contain asbestos, which should be removed only with a special, approved
vacuum collection system or an approved liquid cleaning system.
8. To check clutch pedal free travel, use a tape measure or ruler. Place the tape measure or ruler
beside the clutch pedal with one end against the floor. Note the reading, and then depress the clutch
pedal to take up the free travel. The difference in readings is the clutch pedal free travel.
9. c
10. a. worn clutch bearing
b. weak pressure plate springs
c. loose pilot bearing/bushing in the crankshaft

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Job Sheet 1.2.2 : Perform Underchassis Preventive Maintenance

Learning outcomes:
1.2 Check clutch fluid and lines
Learning Activity:
1.2.3 Check clutch fluid and lines

OK R AC D T Re Specify
(Replace) (Adjust) (Clean) (Disassemble) (Tighte (Repair)
Check n)

1. Clutch line for
leakage

2. Clutch line for
cracks

3. Clutch line for
twists

4. Clutch line for
bends

5. Clutch line for
loose
connections

6. Clutch line for
restriction

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Information Sheet 2.1.1: Components and Functions of Brake System

Learning outcomes:
2 Inspect Brake System
Learning Activity:
2.1.1 Components and Functions of Brake System

Function of Brakes

Diagram of typical automotive brake system

A brake is a device for slowing or stopping the motion of a machine, and to keep it from
starting to move. The kinetic energy lost by the moving part is usually translated to heat by
friction.

When you step on the brake pedal, you are
actually pushing against a plunger in the master
cylinder which forces hydraulic oil (brake fluid)
through a series of tubes and hoses to the
braking unit at each wheel. Since hydraulic fluid
(or any fluid for that matter) cannot be
compressed, pushing fluid through a pipe is just
like pushing a steel bar through a pipe. Unlike a
steel bar, however, fluid can be directed through
many twists and turns on its way to its
destination, arriving with the exact same motion
and pressure that it started with.

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Information Sheet 2.1.1: Components and Functions of Brake System

It is very important that the fluid is pure liquid
and that there are no air bubbles in it. Air can
compress, which causes a sponginess to the
pedal and severely reduced braking efficiency.
If air is suspected, then the system must be bled
to remove the air. There are "bleeder screws" at
each wheel cylinder and caliper for this purpose.

On a disk brake, the fluid from the master
cylinder is forced into a caliper where it presses
against a piston. The piston, in-turn, squeezes
two brake pads against the disk (rotor) which is
attached to the wheel, forcing it to slow down or
stop.

This process is similar to a bicycle brake where
two rubber pads rub against the wheel rim
creating friction.

With drum brakes, fluid is forced into the wheel
cylinder which pushes the brake shoes out so
that the friction linings are pressed against the
drum which is attached to the wheel, causing the
wheel to stop.

In either case, the friction surfaces of the pads
on a disk brake system, or the shoes on a drum
brake convert the forward motion of the vehicle
into heat. Heat is what causes the friction
surfaces (linings) of the pads and shoes to
eventually wear out and require replacement.

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Worksheet 2.1.2. : Perform Underchassis Preventive Maintenance

Learning outcomes:
2 Inspect Brake System
Learning Activity:
2.1.2 Inspect Brake System

Check your knowledge in fluids by completing this worksheet.

1. A chemically-inert hydraulic fluid used to transmit force and motion is called
______________.

2. What are the three types of fluids?

3. Types of fluid which are developed for disc-brake system and developed for higher
temperatures are called ________________.

4. A silicon-based fluid that can take even higher temperatures is called ________________.

5. What are the types of fluids that have a clear to amber color and are hygroscopic?
_____________________ .

6. During braking operation, what causes fluid to overheat and cause the moisture?

7. In the master cylinder, the primary piston is the piston that is: (Choose the correct answer.)
a. directly operated by the pushrod
b. nearest the front-end of the car
c. hydraulically operated by the secondary piston
d. needed only on vehicles with drum brakes

8. What do you call a sensor that turns on a warning light in the instrument panel when brake
fluid is low? ______________________ .

9. Parts of master cylinder that force the piston to return to its released position faster than
fluid can flow back to the master cylinder is called ______________________..

10. What are the component parts of a master cylinder?

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Worksheet 2.1.2. : Perform Underchassis Preventive Maintenance

ANSWER KEY

1. Brake fluid

2. a. DOT 3
b. DOT 4

c. DOT 5

3. DOT 4

4. DOT 5

5. a. DOT 3
b. DOT 4

6. Hard and prolonged braking

7. Letter a

8. Fluid level sensor

9. Return springs

10. locking
 primary piston assembly
 secondary seal
 secondary piston
 primary seal
 spring retainer
 spring
 cylinder body
 proportioner with O' ring
 quick take-up valve
 grommet
 fluid level switch
 reservoir
 diaphragm
 reservoir cover


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Operation Sheet 2.1.2. : Perform Underchassis Preventive Maintenance

Learning outcomes:
2. PULL-OUT AND MOUNT CLUTCH COMPONENTS PARTS
Learning Activity:
2.1 Clutch Service

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Job Sheet 2.2.2: Inspect Brake Lines

Learning outcomes:
2. Inspect Brake lines
Learning Activity:
2.2.2 Inspect Brake lines

R AC D T Re Specify
Check OK (Replace) (Adjust) (Clean) (Disassemble) (Tighten) (Repair)

1. Brake line for
leakage

2. Brake line for
cracks

3. Brake line for
twists

4. Brake line for
bends

5. Brake line for
loose
connections

6. Brake line for
restriction

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Information Sheet 3.1.1: Basic Types of Power Steering Systems

Learning outcomes:
3 Inspect Replace Power Steering Fluid
Learning Activity:
3.1 Basic Types of Power Steering Systems and its Maintenance

POWER STEERING SYSTEMS

Hydraulic Principles Used in Power Steering

Two basic principles are used in all hydraulic power steering systems: (1) Liquids can be
compressed very little; (2) Pressure applied to a liquid makes it act equally in all directions, so
liquids can be used to transmit a force.

Pressure can be multiplied into a force. For instance, connect two cylinders, one ten times as
large in area as the other, by a tube or pipe, as shown below. Apply 100 pounds of pressure to
the liquid in both cylinders and it will produce a force ten times greater (1,000 pounds) in the
piston with the larger area. The pressure will be the same in both cylinders, but in the larger
cylinder, as a result of greater area, it produces a force greater than the pressure.

These basic hydraulic principles are applied to provide hydraulic power steering. A pump is
used to develop pressure and a cylinder to develop force. The pressure at the pump and in the
cylinder, for all practical purposes, is the same but in the cylinder it is multiplied into a work
force. The work force is reduced when pressure is reduced. Oil is the liquid used in hydraulic
power steering systems.

Basic Power Steering Systems

The primary purpose of a hydraulic power
steering system is to provide power assistance
for the driver. All such systems consist of the
same principal components. Note: Large
cylinder has ten times more piston area than
smaller cylinder.

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Information Sheet 3.1.1: Basic Types of Power Steering Systems

Interconnecting hoses and a means of driving the pump are also needed. A V-belt (or belts) is
the usual pump drive, and all components are interconnected to form an oil circuit. Circulation
of the oil is continuous when the engine is running.

Basically, the pump supplies hydraulic fluid under pressure to the control valve, which directs
the fluid to the right or left side of the power cylinder piston, depending upon the direction of
turn being made. The power cylinder, when actuated by this applied pressure, reduces the
amount of effort required at the steering wheel. Arrangement of the principal components
differs according to installation requirements. Some of these are shown in the following
illustrations.

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Information Sheet 3.1.1: Basic Types of Power Steering Systems

In the so-called linkage type, the second valve and power cylinder may be separate parts and
mounted separately in the linkage, (a) or they may be in a single unit known as an in-line unit
(b).
In the semi-integral type the control valve is assembled on the steering gear, and the power
cylinder is mounted in the linkage. In the integral type, the control valve and power cylinders
are an integral part of the steering-gear assembly.

Rack-and-pinion type

The oil pump's control valve structure and operation are basically the same as the ballnut type,
except that the steering gear and power cylinder coupling are as shown below.

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Information Sheet 3.1.1: Basic Types of Power Steering Systems

FLUID LEVEL - The fluid is checked at the pump reservoir with a dipstick attached to the
reservoir cap. However, it is not simply a matter of pulling the cap and reading the dipstick, so
follow the manufacturer's procedure.

FLUID LEAKS - Clean the suspected area, then cycle the wheel from lock to lock several
times. Fluid leakage will not only cause abnormal noises, but may result in unequal and
abnormal steering efforts. If no sign of leakage are apparent, repeat the wheel cycling process
and inspection several more times. Consult the appropriate section of the service manual for
detailed information about the action necessary to correct any leaks.

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Information Sheet 3.1.1: Basic Types of Power Steering Systems

POWER STEERING HOSES - The primary purpose of power steering hoses is to transmit
power (fluid under pressure) from the pump, to the steering gearbox, and to return the fluid
ultimately to the pump reservoir. Hoses also, through material and construction, functions as
additional reservoirs and act as sound and vibration dampers.
Hoses are generally a reinforced synthetic rubber material coupled to metal tubing at the
connecting points. The pressure side must be able to handle pressures up to 1,500 psi. For
that reason, wherever there is a metal tubing to a rubber connection, the connection is
crimped. Pressure hoses are also subject to surges in pressure and pulsations from the pump.
The reinforced construction permits the hose to expand slightly and absorb changes in
pressure.

Where two diameters of hose are used on the pressure side, the larger diameter or pressure
hose is at the pump end. It acts as a reservoir and as an accumulator absorbing pulsations,
The smaller diameter or return hose reduces the effects of kickback from the gear itself. By
restricting fluid flow, it also maintains constant back pressure on the pump, which reduces
pump noise. If the hose is of one diameter, the gearbox is performing the damping functions
internally.

Because of working fluid temperature and adjacent engine temperatures, these hose must be
able to withstand temperatures up to 300ºF. Due to various weather conditions, they must also
tolerate sub-zero temperatures as well. Hose material is specifically formulated to resist
breakdown or deterioration due to oil or temperature conditions.

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Information Sheet 3.1.1: Basic Types of Power Steering Systems

POWER STEERING
The power-steering unit is designed to reduce the amount of effort required to turn the

steering wheel. It also reduces driver fatigue on long drives and makes it easier to steer the vehicle at
slow road speeds, particularly during parking.

Power steering can be broken down into two design arrangements: conventional and non-
conventional or electronically controlled. In the conventional arrangement hydraulic power used to
assist the driver. In the non-conventional arrangement, an electric motor and electronic controls
provide power assistance in steering.

Conventional Power-Steering Systems
There are several power steering systems in use on passenger cars and light-duty tracks. The

most common ones are the external-piston linkage, integral piston, and power-assisted rack and pinion
system.

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Information Sheet 3.1.1: Basic Types of Power Steering Systems

The three major power steering systems. A. Integral-piston linkage B. Rack and pinion
C. External-piston linkage

Power Steering Pump
The steering pump is used to develop hydraulic flow, which provides the force needed to operate the
steering gear. The pump is belt driven from the engine crankshaft, providing flow anytime the engine
is running. It is usually mounted near the front of the engine (Figure 37-28).

Typical Power steering pump location

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Information Sheet 3.1.1: Basic Types of Power Steering Systems
There are four general types of power-steering pumps: roller, vane, slipper, and gear .

Functionally, all pumps operate in the same basic manner. Hydraulic fluid for the power-steering
pump is stored in a reservoir. Fluid is routed to and from the pump by hoses and lines. Excessive
pressure is controlled by a relief valve.

Typical hydro-boost system that uses the power steering pump to power assist brake applications.

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Operation Sheet 4.1.1. : Perform Underchassis Preventive Maintenance

Learning outcomes:
4. PERFORM CLUTCH FAILURE ANALYSIS
Learning Activity:
4.1 CLUTCH FAILURE ANALYSIS

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Worksheet 3.1.2. : Perform Underchassis Preventive Maintenance

Learning outcomes:
3 Inspect /Replace Power Steering Fluid
Learning Activity:
3.1.2 Inspect Replace Power Steering Fluid

Check your mastery of learning outcome #3 by completing this self-check.

1. What is power steering fluid?
a. used as a special power steering fluid
b. the steering axis inclination
c. caused by sagging springs
d. scrub radius

2. Steps to check steering fluid level
a. Open power steering reservoir cap, pull-out dipstick
b. tighten the power steering reservoir plug
c. loosen the power reservoir plug

3. Step to replace fluid level
a. open and drain steering fluid
b. tighten and close power steering drain plug
c. pull-out the power steering pump
d. install power steering pump

4. Step to refill power steering fluid
a. fill-up fluid to the power steering fluid
b. loosen bolt of power steering fluid
c. tighten bolt of power steering fluid
d. cut the hose

5. 5. What is the primary purpose of power steering hose?
a. to lubricate the pump
b. to relieve pressure
c. to transmit power through fluid under pressure
d. none of the above

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Worksheet 3.1.2. : Perform Underchassis Preventive Maintenance

ANSWER KEY

1. A
2. A
3. A
4. A
5. C

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Information Sheet 4.1.1: Classification and Viscosity of Fluid

Learning outcomes:

4 Inspect /change Transmission/Differential Fluid

Learning Activity:

4.1.1 Classification and viscosity range data of fluid

AUTOMATIC TRNAMISSION FLUID
ATF can be petroleum based, partially synthetic, or totally synthetic-based oil. All domestic

automobile manufacturers require a petroleum-based fluid in their automatic transmissions; however,
some imported vehicles require the use of a partially synthetic fluid.

ATF is a compound liquid that also includes special additives, which allow the lubricant to better
meet the flow and friction requirements of an automatic transmission. ATF is normally dyed red,
primary to help distinguish it from the engine oil when determining the source of fluid leaks.

Petroleum-based ATF typically has a clear red color and will darken when it is burnt or become
milky when contaminated by water. Synthetic ATF is normally a darker red than petroleum-based
fluid. Synthetic fluids tend to look and smell burnt after normal use; therefore, the appearance and
smell of these fluids is not a good indicator of the fluid’s condition.

The various chemicals added to ATF ensure the durability and overall performance of the fluid.
Zinc, phosphorous, and sulphur are commonly added to reduce friction. Detergent additives are added
to ATF to help keep the transmission parts clean. Also added are dispersant that keeps contaminants
suspended in the fluid so they can be trapped by the filter.

FLUID SERVICE
The ATF level should be checked at regular mileage and time intervals. The dipstick is located

on the transmission housing at the end of the engine opposite the belts and pulleys.
Make sure the vehicle is level. On most automobiles, the ATF level can be checked accurately

only when the transmission is at operating temperature. For most vehicles, the engine must be
running and the shift lever placed in either park or neutral, as specified by the vehicle manufacturer,
with the parking brake applied. Markings on a dipstick indicate add levels, plus full levels for fluid
when cool, warm, or hot.

Typical transaxle dipstick indicating proper ATF levels at various operating temperatures

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Information Sheet 4.1.1: Classification and Viscosity of Fluid
Some dipsticks have readings on both sides. Others have readings on only one side. On some

vehicles with automatic transaxles, the cold fluid level might be higher than the hot fluid level. Refer
to the manufacturers’ service manual and service bulletins for specific information.

To check the fluid level, start the engine and bring it to the operating temperature. Remove the
dipstick and wipe it clean with a lint-free cloth or paper towel. Reinsert the dipstick fully. Remove it
again and note the reading.

Removing the Transmission pan drain plug

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Worksheet 4.1.2. : Perform Underchassis Preventive Maintenance
Learning outcomes:
4 Inspect Change Transmission/Differential Fluid
Learning Activity:
4.1.2 Inspect change Transmission/Differential Fluid

Answer the following questions.
1 What are the five jobs that gear oil does?
2 In order to improve the gear oil’s load-carrying capacity we mix it with

_________________.
3 What do we call the oil that has an additive in it to increase load-carrying capacity?
4 Enumerate the types of gear that most cars and light trucks use?
5 Identify the component parts of differential.
6 Identify the component parts of transmission

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Worksheet 4.1.2. : Perform Underchassis Preventive Maintenance

ANSWER KEY

1 a. to lubricate all moving parts and prevent wear
b. to reduce friction and power loss
c. to protect against rust and corrosion
d. to keep the interior clean
e. to cool the gearbox

2. Chemical additives

3. extreme pressure lubricant

4. a. SAE 75W
b. 75W-80
c. 80W-90
d. 85W-90

5. Refer your answer to resource material provided

6. Refer your answer to resource material provided

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Information Sheet 5.1.1 : Perform Underchassis Preventive Maintenance

Learning outcomes:
5 Check Tires and Pressure
Learning Activity:
5.1.1 Types of Tire Purpose and Construction

TIRES
The primary purpose of tires is to provide traction. Tires also help the suspension absorb road shocks,
but this is a side benefit. They must perform under a variety of conditions. The road might be wet or
dry; paved with asphalt, concrete, or gravel; or there might be no road at all. The car might be
travelling slowly on a straight road, or moving quickly through curves or over hills. All of these
conditions call for special requirements that must be present, at least to some degree, in all tires.

In addition to providing good traction, tires are also designed to carry the weight of the vehicle,
withstand side trust over varying speeds and conditions, and transfer braking and driving torque to the
road.

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Information Sheet 5.1.1 : Perform Underchassis Preventive Maintenance

Types of construction

There are three types of tire construction in use today (Figure 35-5). They are bias ply, belted bias ply,
and radial ply tires.

Tire Ratings and Designations (Figure 35-7)

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Information Sheet 5.1.1 : Perform Underchassis Preventive Maintenance

TIRE CARE
To maximize tire performance, inspect the signs of improper inflation and uneven wear, which can
indicate a need for balancing, rotation, or front suspension alignment. Tire should be checked
frequently for cuts, stone bruises, abrasions, blisters, and objects that might have become imbedded in
the thread. More frequent inspections are recommended when rapid or extreme temperature
changes occur, or where the road surfaces are rough or occasionally littered with debris.

To clean tires, use a mild soap and water solution only. Rinse thoroughly with clear water. Do
not use any caustic solutions or abrasive materials. Never use steel wool or wire brushes. Avoid
gasoline, paint thinner, and similar materials having a mineral oil base. These materials are harmful to
the tires and eventually discolor the whitewalls and raised letters.

Inflation Pressure.

Figure 1. Effects on Inflation of tires Figure 2. Tire profile on a nonradial tire as
compared to a radial tire.

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Information Sheet 6.1.3 : Perform Underchassis Preventive Maintenance

Learning outcomes:
6 Bleed Hydraulic Clutch System
Learning Activity:
6.1.3 Procedures in Hydraulic Clutch System Bleeding

Introduction

Automotive components are held together with fasteners. As a technician, you will spend
much of your day removing and replacing fasteners. These small parts are very important. If
fasteners are not used properly, the components they hold together can fail.

Many different types of a fasteners are used on an automobile (Figure 5-1). Fasteners
can be divided into two basic groups. Threaded fasteners use the clamping force from the
threads to hold parts together. Nonthreaded fasteners hold parts together without threads.
Both types are discussed in the following sections.

Threaded Fasteners

Threads provide a mechanical advantage to hold parts. The geometry behind threads was
developed a long time ago, around 200 B.C. They were used by the ancient Romans to press
the grapes for wine.

Threaded fasteners are the most common fastener type. They are spirals called
threads to wedge parts together. The common types o threaded fasteners are screw, bolts,
studs, and nuts and are shown in Figure 6-1.

Figure 6-1 Common types of threaded automotive fasteners.

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Information Sheet 6.1.3 : Perform Underchassis Preventive Maintenance

Hardness and Strength

Bolts and hex head screws used for different parts of the automobile have different strength
requirements. A hex head cap screw used to hold on an engine flywheel must be much
stronger than one used to hold on a headlight. On the other hand, the fasteners made to hold
on the flywheel are much more expensive than the ones used on the headlight.

The strength or quality of fasteners is identified by grade marking on the fasteners. The
marking are different for U.S. (English) and metric fasteners. The U.S. (English) grade
markings for bolts and hex head cap screw are shown (Figure 6-2). The standards are set by
the Society of Automotive Engineers (SAE). The systems uses marks on the head of the bolt
or the next head cap screw. Unfortunately, the system is confusing because the number of
marks and the grade number does not agree. A grade0,1, and 2 bolt has no markings on the
head and is not very strong. A bolt with 3 marks is called a grade 5 bolt and is much stronger
than a grade 1. The strongest bolt for automotive use has six marks and is called a grade 8.
The chart in figure also 6-3 describes the material each grade is made from the tensile
strength. Tensile strength is the amount of pressure the fasteners can take before it breaks.

Metric fasteners use property class numbers to indicate their strength. These numbers
are stamped on the head of the bolt or hex head cap screw. Typical metric bolt strength
numbers are shown (Figure 6-4). The higher the property class number, the stronger the
fastener. A 10.9 fastener is much is much stronger than one marked 4.6. A metric fastener
without a number would be the same as a grade 0 U.S. (English) fastener. Metric studs have
a marking system on the end of the stud that shows their property class number, as shown in
Figure 6-4.

Common Metric Head Sizes

Wrench Size Wrench Size

9 mm 19 mm

10 mm 20 mm

11 mm 21 mm

12 mm 22 mm

13 mm 23 mm

14 mm 24 mm

15 mm 26 mm

16 mm 27 mm

17 mm 29 mm

18 mm 30 mm

32 mm

Figure 6-2 Common metric head and wrench
sizes.

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Information Sheet 6.1.3 : Perform Underchassis Preventive Maintenance

Figure 6-2 Grade marking system for U.S. (English) bolts and hex head cap screw.
Figure 6-3 Grade marking system for metric bolts, hex, head cap screw, and studs.

Figure 6-4 Grade marking system used for U.S. (English) and metric nuts.

WARNING: Always replace the fasteners with the same strength (grade markings) as
the one they replace. Failure to do so may cause the par to fail.

Nuts are also graded according to the same grading system as shown (Figure 5-19).
Nuts must have the same grade as the bolts or studs with which they are used. English nuts
have dots that represent grade markings. Three dots represent a grade 5. Sit dots represent

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Information Sheet 6.1.3 : Perform Underchassis Preventive Maintenance

a grade8. Metric nuts have numbers that represent strength. The number on the nut is its
property class number. In both systems the higher the number or the more dots, the stronger
the nut.

Using a Pitch Gauge

WARNING: Always start threaded fasteners several turns into their mating threads by
hand. Never start a fastener with a wrench. If the fastener is the wrong thread size, the
threads can be damaged by the force of the wrench.

There are two different threads system in use, each with fine and coarse threads, which
can cause a great deal of confusion. Metric threads cannot be used with English threads.
Fine threads cannot be used with coarse threads. These different types of threads can make it
difficult for the technician to tell one thread from another.

A thread pitch gauge (Figure 6-5) is used to identify fasteners. Is has a number of
blades with teeth. The thread size is written on the blade. By matching the teeth on the blade
with threads on a fastener, you can determine thread size. Pitch gauges are made for both
metric and English threads.

Fastener Torque

Each threaded fastener on an automobile must be tightened just the correct amount.
Untightened fasteners can loosen and cause parts to fail. Fasteners that are tightened too
tightly can damage the part of the fastener and cause the parts to fail. Overtightening causes
it to stretch like those shown (Figure 6-6). These no longer have the strength they had before
the overtightening.

Figure 6-5 A pitch gauge is used to match Figure 6-6 These fasteners have the threads
distorted and stretched from overtightening.
Threads for identification. (Courtesy off
Central Tools)

To avoid these problems, fasteners must be tightened with a torque wrench. There are
torque specifications charts for each important fastener in the service manual for the car you
are working on. Always follow these specifications.

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Information Sheet 6.1.3 : Perform Underchassis Preventive Maintenance
Figure 6-7 Repairing minor thread damage with a tap.

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Operation Sheet 6.1.1. : Perform Underchassis Preventive Maintenance

Learning outcomes:
6. BLEED CLUTCH HYDRAULIC SYSTEM
Learning Activity:
6.1.1 Procedure in Hydraulic Clutch Bleeding

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