AUTOMOTIVE 104
Engr. Lemuel John M. Desamero
Engr. King Edsel Isleta
VISION
Laguna University shall be a socially responsive educational
institution of choice providing holistically developed
individuals in the Asia-Pacific Region.
MISSION
Laguna University is committed to produce academically
prepared and technically skilled individuals who are socially
and morally upright citizens.
Department of Mechanical Engineering
MISSION
The Department of Mechanical Engineering of Laguna
University is committed to produce academically prepared
and technically skilled mechanical engineers who are socially
and morally upright citizens.
VISION
The Department of Mechanical Engineering of Laguna
University is envisioned to be the provincial college of choice
producing well-equipped mechanical engineers who
specializes on energy management.
Table of Contents
Module 1: Introduction to automobile
Introduction
Learning Objectives
Lesson 1. Purpose of the clutch
Lesson 2. Function of the clutch
Lesson 3. Starting the Engine and Shifting Gears
Assessment Task 1
Summary
References
1
1
1
1
2
4
5
5
5
Module 2: Clutch Construction
Introduction
Learning Objectives
Lesson 1: Clutch Construction
Lesson 2: Clutch Operation
Lesson 3: Release Bearing
Lesson 4: Friction Disc
Lesson 5: Coil-Spring Clutch
Lesson 6: Diaphragm-Spring Clutch
Assessment Task 2
Summary
References
6
6
6
6
7
7
8
10
11
12
12
13
Module 3: Clutch Linkage
Introduction
Learning Objectives
Lesson 1: Clutch Linkage
Lesson 2: Cable Clutch Linkage
Lesson 3: Hydraulic Clutch Linkage
Lesson 4: Electronically Controlled Clutch
Assessment Task 3
Summary
References
14
14
14
14
15
16
17
18
19
19
Module 4: Electronically Controlled Clutch
Introduction
Learning Objectives
Lesson 1: Clutch Safety Switch
Lesson 2: Clutch Trouble Diagnosis
Assessment Task 4
Summary
References
21
21
21
21
22
27
28
28
Course Code:
AT 104
Course Description: For student interest in the automobile from a business,
technical, and/or consumer perspective subject covered include automotive career
exploration, consumer information, minor maintenance and safety inspection, and
an introduction to technical system. Also automotive history and current social issue
associated with automobile, prerequisites;
Course Intended Learning Outcomes (CILO):
At the end of the course, students should be able to:









Diagnose and repair all major vehicle systems.
Document repairs of vehicles accurately and descriptive of concern, cause,
and correction.
Effectively locate and utilize technical information required for vehicle
repairs.
Work safely and responsibly within all shop standards and environmental
guidelines.
Successfully pass at least two Automotive Service Excellence (ASE) technical
skill assessments.
Function collaboratively as a member of a team to achieve specified and
measurable results.
Comprehensive knowledge of employer expectations and ethical work
practice.
Demonstrate accuracy, proficiency and quality in task performance.
Strategize professional growth in automotive industry.
Course Requirements:
Assessment Tasks - 60%
Major Exams
- 40%
_________
Periodic Grade
100%
Computation of Grades:
PRELIM GRADE
= 60% (Activity 1-4)+ 40% (Prelim exam)
MIDTERM GRADE = 30%(Prelim Grade) + 70 %[60% (Activity 5-7) + 40% (Midterm exam)]
FINAL GRADE
= 30%(Midterm Grade) + 70 %[60% (Activity 8-10) + 40% (Final exam)]
MODULE 1
Clutch Construction and Operation
Introduction
The automotive drive train or power train carries power from the engine to the drive
wheels. In vehicles with manual transmission or manual transaxle, the power flows through a
clutch. This device couples and uncouples the manual transmission or transaxle and the
engine. The clutch is usually operated by the driver’s foot. Some clutches have a power-assist
device to reduce driver effort. Various electronic devices may be used so that the clutch
operates automatically (Crouse and Anglin, 2004).
The clutch is located between the engine flywheel and the transmission or transaxle.
This engine mounts longitudinally, the clutch location in a front-wheel-drive car with a
transversely-mounted engine (Crouse and Anglin, 2004).
Learning Outcomes
At the end of this module, students should be able to:
1. Identify the purpose of clutch.
2. Distinguish every function of clutch.
Lesson 1: Purpose of the clutch
Movement of a foot pedal operates the clutch. When the driver pushes the clutch pedal
down, the clutch disconnects or disengages from the engine flywheel. No engine power can
1
flow through the transmission or transaxle. When the driver releases the clutch pedal, the
clutch engages. This allows power to flow through (Crouse and Anglin, 2004).
Lesson 2: Functions of the Clutch
The clutch has four functions
1. It can be disengaged (clutch pedal down). This allows engine cranking and permits
the engine to run freely without delivering power to the transmission (Crouse and
Anglin, 2004).
2. While disengaged (clutch pedal down), it permits the driver to shift the transmission
into various gears. This allows the driver to select the proper gear (first, second, third,
fourth, fifth, reverse, or neutral) for the operating condition (Crouse and Anglin, 2004).
3. While engaging (clutch pedal released), the clutch slips momentarily. This provides
smooth engagement and lessens the shock on gears, shaft, and other drivetrain parts.
As the engine develops enough torque to ever come the inertia of the vehicle. The
drive wheels turn and the vehicle begins to move (Crouse and Anglin, 2004).
4. When engaged (clutch pedal released), the clutch transmits power from the engine to
the transmission. All slipping has stopped (Crouse and Anglin, 2004).
2
Figure 1.1 Longitudinal Engine with Front Wheel Drive, Showing the Clutch and Five Speed
Manual Transmission (Crouse and Anglin, 2004)
Figure 1.2 Clutch Location between Transverse Engine and Manual Transaxle in a Front
Wheel Drive Car (Crouse and Anglin, 2004).
3
Figure 1.3 Depressing The Foot Pedal, Or Clutch Pedal, Operates The Clutch ( Crouse
and Anglin, 2004).
Lesson 3: Starting the Engine and Shifting Gears
The automotive engine cannot start under load. To remove the load, place the gear
shift lever of transmission shift lever in neutral or disengage the clutch either action disconnect
engine flywheel from the engine transmission. No power can flow through (Crouse and Anglin,
2004).
An automotive engine will normally start when cranked at 200 rpm (revolution per
minute) or higher. After the engine start and with the clutch pedal down, the driver moves the
gearshift lever form neutral to first gear. As the driver releases the clutch pedal, spring force
in to the clutch causes it to engage. Power flow through the transmission to the drive wheels
and the vehicle moves. To increase vehicle speed, the driver then disengages the clutch and
shifts the transmission to higher gear (Crouse and Anglin, 2004).
4
Assessment Task 1
Define and explain in your own words the four functions of a clutch system (Hand
Written)
1.
2.
3.
4.
Summary

Movement of a foot pedal operates the clutch. When the driver pushes the clutch pedal
down, the clutch disconnects or disengages from the engine flywheel (Crouse and
Anglin, 2004).

The automotive engine cannot start under load (Crouse and Anglin, 2004).

An automotive engine will normally start when cranked at 200 rpm (revolution per
minute) or higher (Crouse and Anglin, 2004).
Reference
Crouse, W. and Anglin, D. (2004). Automotive Mechanics 10th Edition, International Edition
5
MODULE 2
Clutch Construction
Introduction
The typical clutch consists of three basic parts. These are the engine flywheel a friction
disc, and a pressure plate. The flywheel; and pressure plate are the drive or driving members.
they attach to and rotate with the engine crank shaft. The friction disc is a driven member (also
called the driven plate and drive disc). It is 12 inches (302mm) or less in diameter and splined
to the clutch shaft or transmission input shaft. Both must turn together, but the friction disc
can slide back and forth on the shaft-splines (Crouse and Anglin, 2004).
Learning Outcomes
At the end of this module, students should be able to:
1. Identify the construction of clutch
2. Determine the operation of clutch.
Lesson 1: Clutch Construction
The pressure plate, with one or more spring, attaches to the clutch cover. This
pressure-plate assembly bolts to the flywheel and rotates with it. Spring force holds the friction
disc against the flywheel while the clutch is engaged (Crouse and Anglin, 2004).
The transmission input shaft has the same centerline as the engine crankshaft, the
small end of the input shaft riders in a pilot bearing or bushing in the end of the crankshaft.
6
The transmission front bearing or transmission-input-shaft bearing supports the other end of
the input shaft (Crouse and Anglin, 2004).
Lesson 2: Clutch Operation
Disengaging the clutch (pushing the clutch pedal down) moves the pressure plate
away from the friction disc. Releasing the clutch pedal engages the clutch; spring force clamps
the friction disc between the pressure plate and flywheel. Then the friction disc and
transmission input shaft turn with the flywheel (Crouse and Anglin, 2004).
In many clutches, when the driver depresses the clutch pedal, linkage to the clutch
fork causes it to pivot. The fork pushes against the release bearing or throw-out bearing. This
forces the release bearing inward against release fingers or levers in the pressure-plate
assembly. These pivot to push the pressure plate away from the friction disc (Crouse and
Anglin, 2004).
As the pressure plate moves away from the friction disc, a slight air gap opens between
the pressure plate and the friction disc. Another air gap appears between the friction disc and
the flywheel. These gaps disengage the clutch so no power flows through it. The typical friction
travels about 0.060 inch [1.5mm] as it moves from engaged to disengaged (Crouse and
Anglin, 2004).
Lesson 3: Release Bearing
When the driver depresses the clutch pedal, the clutch linkage moves the release
bearing or throw-out bearing. The bearing travel pushes or pulls the release levers or fingers
inward or outward to disengage the clutch (Crouse and Anglin, 2004).
The type of clutch linkage determines the type of release bearing. Most are ball
bearings, but they vary in construction and operation (Crouse and Anglin, 2004).
Depressing the clutch pedal forces the release bearing against release levers. This
starts the release bearing rotating. Letting up the clutch pedal moves the release bearing away
7
form the pressure plate. The release bearing must travel far enough so there is some
clearance or freeplay between the release levers and the bearing. If not, the bearing continues
rotating. Then this type of release bearing will overheat and fail. It may also cause the clutch
to slip (Crouse and Anglin, 2004).
Figure 2.1 Release Bearing (ASE Certification Practice Tests, n.d.)
Release bearings used with self-adjusting clutches (cable and hydraulic linkage).
These require a slight preload. The bearing lightly touches the fingers. This causes the bearing
to rotate continuously as long as the engine runs. These bearings also are preloaded and
rotate when the engine runs (Crouse and Anglin, 2004).
Lesson 4: Friction Disc
It has a hub and plate, cushion springs, and dampening springs. The slightly-waved
cushion springs attach to the plate. The friction facing attach to the cushion springs. When the
clutch engages, the cushion springs compress slightly to take up the shock of engagement
(Crouse and Anglin, 2004).
8
The dampening springs or torsional springs are heavy coil springs set in a circle
around the hub. The hub is driven through these springs. They help reduce the torsional
vibration caused by the engine power impulses, this smoothens the power flow to the
transmission (Crouse and Anglin, 2004).
Figure 2.2 Friction Disc Clutch System (Rajvanshi, 2016).
There are grooves on both sides of the friction-disc facing. These grooves prevent the
facing from sticking to the flywheel face and pressure plate when the clutch disengages. The
grooves break any vacuum that might form and cause the facings to stick. They also help cool
the facings (Crouse and Anglin, 2004).
The facing on many friction discs are made of cotton and asbestos fibers woven or
molded together. Then the material is saturated with resins or other binding agents. Copper
wire is woven or pressed into the facing of some friction disc to give them added strength.
However, asbestos is a health hazard and is being replaced with other material. Some friction
discs have ceramic-metallic faces (Crouse and Anglin, 2004).
9
Lesson 5: Coil-Spring Clutch
The clamping force in the pressure-plate assembly is provided by a single diaphragm
spring or by several coil springs. These are set in a circle between the cover and the pressure
plate. Depressing the clutch pedal forces the release bearing against the release levers.
These pivot on eyebolts. Struts then carry the motion to the pressure plate. It moves away
from the friction disc, compressing the spring against the clutch cover. This disengages the
clutch (Crouse and Anglin, 2004).
Releasing the clutch pedal allows the coil springs to extend. They again clamp the
friction disc between the pressure plate and the flywheel. This engages the clutch (Crouse
and Anglin, 2004).
The coil springs must be strong enough to prevent clutch slippage. However, the
stronger the springs, the harder the driver must push on the clutch pedal. One solution is to
use a semi centrifugal clutch. It has weights on the ends of the release levers. As speed
increases, centrifugal force causes the weights to add to the force of the springs. As speed
increases, the rollers move out to increase the clamping force on the friction disc (Crouse and
Anglin, 2004).
Figure 2.3 Coil Springs for Clutch System (Acxess Spring, n.d.)
10
Lesson 6: Diaphragm-Spring Clutch
The diaphragm-spring clutch is used with most manual transaxles and in many rearwheel-drive vehicles. A Belleville spring or diaphragm spring supplies the force that holds the
friction disc against the flywheel. The spring has tapered fingers pointing inward from a solid
ring. These act as release levers to take up the spring force as the clutch disengages. The
diaphragm acts like the bottom of oil can. After it is pushed inward, it will “spring” back when
the applying force is released (Crouse and Anglin, 2004).
As the driver depresses the clutch pedal, the release bearing pushes against the
fingers on the diaphragm spring. This causes the diaphragm to pivot about the inner pivot ring
and dish inward as it does so, the outer section moves in the opposite direction and pushes
the pressure plate away from the friction disc. This disengages the clutch. Spring force varies
according to the size and thickness of the diaphragm spring (Crouse and Anglin, 2004).
Figure 2.3 Coil Springs for Clutch System (Jamiebcmr2, 2013)
11
Some cars use a diaphragm-spring pull clutch. The release bearing has a flange that
rides on the inside surface of the diaphragm-spring fingers. Depressing the clutch pedal
causes the fork to pull the release bearing and fingers outward. This pulls the pressure plate
away from the friction disc and disengages the clutch (Crouse and Anglin, 2004).
Assessment Task 2
Answer the following in HAND WRITTEN form.
1. Give the functions of the following
a. Release Bearing
b. Friction disc
c. Coil spring clutch
d. Diaphragm spring clutch
2. What are the similarities and differences of Coil spring and Diaphragm spring?
Provide drawings to better explain.
Summary

The pressure plate, with one or more spring, attaches to the clutch cover. This
pressure-plate assembly bolts to the flywheel and rotates with it (Crouse and Anglin,
2004).

The dampening springs or torsional springs are heavy coil springs set in a circle
around the hub. The hub is driven through these springs (Crouse and Anglin, 2004).

The facing on many friction discs are made of cotton and asbestos fibers woven or
molded together (Crouse and Anglin, 2004).

The clamping force in the pressure-plate assembly is providing by a single diaphragm
spring or by several coil springs (Crouse and Anglin, 2004).
12

Releasing the clutch pedal allows the coil springs to extend. They again clamp the
friction disc between the pressure plate and the flywheel (Crouse and Anglin, 2004).

The coil springs must be strong enough to prevent clutch slippage. However, the
stronger the springs, the harder the driver must push on the clutch pedal (Crouse
and Anglin, 2004).

The diaphragm-spring clutch is used with most manual transaxles and in many rearwheel-drive vehicles (Crouse and Anglin, 2004).

As the driver depresses the clutch pedal, the release bearing pushes against the
fingers on the diaphragm spring (Crouse and Anglin, 2004).

Some cars use a diaphragm-spring pull clutch. The release bearing has a flange that
rides on the inside surface of the diaphragm-spring fingers (Crouse and Anglin,
2004).
Reference
Acxess Spring. (n.d.). Clutch Springs. 2225 E. Cooley Dr. Colton, CA 92324. Retrived from:
https://www.acxesspring.com/clutch-springs.html
ASE
Certification
Practice
Tests.
(n.d.).
FreeASEStudyGuides.com.
Clutch
Release
Retrieved
Bearing.
from:
https://www.freeasestudyguides.com/clutch-release-bearing-noise.html
Crouse, W. and Anglin, D. (2004). Automotive Mechanics 10th Edition, International Edition
DESIGN AND STRUCTURAL ANALYSIS OF SINGLE PLATE FRICTION CLUTCH.
Retrieved from: http://www.engineersgallery.com/design-structural-analysis-singleplate-friction-clutch/
Jamiebcmr2.
(2013).
Diaphragm
Spring
Clutch.
Retrieved
from:
https://www.thinglink.com/scene/455376996478746626
13
MODULE 3
Clutch Linkage
Introduction
Sometimes a clutch with greater holding power is needed. When limited space
prevents making the clutch larger, then a clutch with two friction discs can be used. This
provides greater holding force. Double-disk coil-spring clutches are also available. These
clutches are used in medium and heavy trucks. Use of the second friction disc adds clutchplate area, thereby providing greater torque-carrying capacity. When the clutch is engaged,
each friction disc transmits half of the flywheel torque to the input shaft. These clutches are
operated and work in the same way as single-disc clutches (Crouse and Anglin, 2004).
Learning Outcomes
At the end of this module, students should be able to:
1. Identify different kinds of clutch linkage
2. Determine the similarities and differences of each kind.
Lesson 1: Clutch Linkage
The parts that connect the clutch pedal to the release bearing make up the clutch
linkage. It is either mechanical (rod or cable) or hydraulic. They all convert a light force applied
to the clutch pedal into a greatly increased force that moves the release bearing.It is used on
many rear-wheel-drive vehicles. Many front-wheel-drive cars have self-adjusting cable
linkage. A variety of vehicles use hydraulic clutch linkage (Crouse and Anglin, 2004).
14
Lesson 2: Cable Clutch Linkage
On many vehicles, it is simpler for the manufacturer to install a cable system than to
develop a rod arrangement. The cable operates the release bearing by movement of the
clutch fork. The fork passes through a boot or dust cover that seals the fork opening in the
clutch housing. This prevents dirt, dust, and water from entering the clutch through the
opening (Crouse and Anglin, 2004).
Cable linkage may be self-adjusting. This eliminates the need for routine clutch
adjustment. The cable for the self-adjusting clutch attaches to a spring-loaded quadrant gear.
It attaches to the clutch pedal through a shaft. A toothed pawl or pivoted arm at the top of the
clutch pedal engages the quadrant-gear teeth. As the clutch pedal is depressed, the pawl
rotates the quadrant gear. This pulls the cable and disengages the clutch (Crouse and Anglin,
2004).
Figure 3.1 Cable Clutch Linkage (Integrated Publishing, n.d.)
15
Self-adjustment occurs when the clutch pedal is released. The spring-loaded quadrant
gear may continue to rotate slightly after the pedal returns to its stop. If friction disc wear has
occurred, the pawl engages a new tooth on the quadrant gear the next time the pedal is
depressed. This adjusts the effective length of the linkage to maintain the proper freeplay or
free travel. The result is correct clutch-pedal height and release-bearing preload (Crouse and
Anglin, 2004).
Lesson 3: Hydraulic Clutch Linkage
Hydraulic-operated clutch linkage is used when the clutch location makes it difficult to
run a rod or cable to it. Hydraulic clutch linkage is also used on high-performance engines.
These have strong springs in the pressure-plate assembly and would require high pedal effort
(Crouse and Anglin, 2004).
Operation of the hydraulic-clutch linkage begins when the driver depresses the clutch
pedal. This forces a pushrod into the master cylinder. Pressurized fluid is then forced from the
master cylinder, through a hydraulic line, to a servo or slave cylinder. A servo is a device that
converts hydraulic pressure to mechanical movement (Crouse and Anglin, 2004).
Figure 3.2 Cable Clutch Linkage (Eric The Car Guy, n.d.)
16
The pressurized fluid then pushes a piston a pushrod out of the servo. The pushrod
movement operates the clutch fork and disengages the clutch (Crouse and Anglin, 2004).
The hydraulic system can be designed so a light force on the clutch pedal produces a
heavy force on the clutch fork. This is done using small piston in the master cylinder and a
large piston in the servo. Operation of hydraulic clutch linkage is similar to a hydraulic brake
system (Crouse and Anglin, 2004).
The servo and the release bearing are included in and assembly that fits on the
transmission front-bearing retainer. One end of the servo seats against the front of the
transmission case. The release bearing attaches to the bearing carrier on the servo piston at
the other end (Crouse and Anglin, 2004).
When the clutch pedal is depressed, hydraulic fluid flows from the clutch master
cylinder to the servo. The fluid pushes the servo piston out of the cylinder. This forces the
release bearing against the finger of the pressure plate and disengages the clutch (Crouse
and Anglin, 2004).
Lesson 4: Electronically Controlled Clutch System
This is a hydraulic-operated clutch that is electronically controlled. No clutch pedal is
needed. Sensor sends information about the operation of the throttle, engine, clutch and
transmission to an electronic control module (ECM). When the driver moves the gearshift
lever, the ECM then signals the hydraulic power pack. It controls the fluid pressure in the
hydraulic cylinder to engage or disengage the clutch. The clutch disengages quickly and
remains disengaged until the driver releases the gearshift lever (Crouse and Anglin, 2004).
There are other types of automatic clutches. They all disengage when the control unit
sends the proper signals to an electronic, hydraulic, pneumatic, or vacuum actuator. The car
may not have a clutch pedal (Crouse and Anglin, 2004).
17
Figure 3.3 Electronically Controlled Clutch System (What-When-How, n.d.)
Assessment Task 3
Give the similarities and differences of the different clutch linkages. Provide
drawings to better explain. (Hand Written)
1. Cable Clutch Linkage
2. Hydraulic Clutch Linkage
3. Electronically Controlled Clutch System
18
Summary

The parts that connect the clutch pedal to the release bearing make up the clutch
linkage. It is either mechanical (rod or cable) or hydraulic (Crouse and Anglin, 2004).

Cable linkage may be self-adjusting. This eliminates the need for routine clutch
adjustment (Crouse and Anglin, 2004).

Self-adjustment occurs when the clutch pedal is released. The spring-loaded
quadrant gear may continue to rotate slightly after the pedal returns to its stop
(Crouse and Anglin, 2004).

Hydraulic-operated clutch linkage is used when the clutch location makes it difficult
to run a rod or cable to it (Crouse and Anglin, 2004).

Hydraulic-operated clutch linkage is used when the clutch location makes it difficult to
run a rod or cable to it (Crouse and Anglin, 2004).

Operation of the hydraulic-clutch linkage begins when the driver depresses the clutch
pedal (Crouse and Anglin, 2004).

The pressurized fluid then pushes a piston a pushrod out of the servo. The pushrod
movement operates the clutch fork and disengages the clutch (Crouse and Anglin,
2004).

The hydraulic system can be designed so a light force on the clutch pedal produces a
heavy force on the clutch fork (Crouse and Anglin, 2004).

The servo and the release bearing are included in and assembly that fits on the
transmission front-bearing retainer (Crouse and Anglin, 2004).

The servo and the release bearing are included in and assembly that fits on the
transmission front-bearing retainer (Crouse and Anglin, 2004).

When the clutch pedal is depressed, hydraulic fluid flows from the clutch master
cylinder to the servo (Crouse and Anglin, 2004).
Reference
Crouse, W. and Anglin, D. (2004). Automotive Mechanics 10th Edition, International Edition
Eric
The
Car
Guy
(n.d.).
PROBLEMS/MANUAL
HOME/FAQ
PAGE/SOLVING
TRANSMISSIONS/HYDRAULICALLY
TRANSMISSION
OPERATED
19
CLUTCHES.
Kings
Mills,
OH
45034.
https://www.ericthecarguy.com/hydraulically-operated-clutches/
Retrieved
from:
Integrated Publishing. (n.d.). Clutch Construction. Integrated Publishing, Inc. - A (SDVOSB)
Service
Disabled
Veteran
Owned
Small
Business.
Retrieved
from:
http://constructionmanuals.tpub.com/14273/css/Clutch-Contruction-135.htm
What-When-How. (n.d.). In Depth Tutorials and Information. Electronically Controlled Semiautomatic Transmission (Automobile).
Retrieved from:
https://what-when-
how.com/automobile/electronically-controlled-semi-automatic-transmissionautomobile/
20
MODULE 4
Clutch Safety and Trouble Shooting
Introduction
Most drivers would expect their clutches to last 40,000 to 60,000 miles, but if you treat
your clutch properly it may be good for your vehicle's life, depending on the type of vehicle
you are driving and how you are driving it (Sclar, n.d.).
Most new manually driven vehicles have self-adjusting clutches that do not need
adjustment, but if you have an older model without self-adjustment, you can minimize wear
on your clutch disk by keeping your clutch pedal balanced properly (Sclar, n.d.).
Learning Outcomes
At the end of this module, students should be able to:
1. Determine automotive safety in clutch systems
2. Identify the common troubles experienced with clutch systems
3. Provide solutions to identified troubles
Lesson 1: Clutch Safety Switch
Many vehicles with a clutch have a clutch safety switch or starter-clutch interlock
switch. It prevents cranking if the clutch is engaged. The clutch pedal must be depressed or
the engine will not crank when the ignition key is turned to start. The movement of the clutch
pedal closes the safety switch. This completes the electrical circuit to the starting motor
(Crouse and Anglin, 2004).
21
The clutch safety switch prevents starting with the transmission in gear and the clutch
engaged. If this happened, the car might move before the driver is ready (Crouse and Anglin,
2004).
The clutch safety switch is a three-function switch:
1. It requires the clutch pedal depressed before the engine will crank (Crouse and Anglin,
2004).
2. It disengages the speed-control system when the clutch pedal is depressed (Crouse
and Anglin, 2004).
3. It sends a fuel-control signal to the ECM in the electronic engine-control system when
the clutch pedal is depressed (Crouse and Anglin, 2004).
Lesson 2: Clutch Trouble Diagnosis
Clutch troubles
Many different troubles can develop in the clutch, producing various conditions and
complaints from the driver. The chart in list common clutch troubles, their possible causes,
and checks or corrections to make. Following sections further explain how to locate and
correct clutch troubles. Other clutch troubles and causes are described in the vehicle service
manual (Crouse and Anglin, 2004).
For proper operation of the clutch and transmission, their common centerline must be
maintained. Dowel pins or alignment sleeves on the back of the block maintain the alignment
between the block and the clutch housing. However, wear or damage of either the pilot bearing
or the transmission-input-shaft bearing may allow the clutch centerline drop. A variety of clutch
and transmission troubles can result. These are the pilot bearing, release bearing and
transmission-input-shaft bearing. Failure of either bearing may cause clutch-system noise
(Crouse and Anglin, 2004).
22
Table 4.1 List of Troubles, Probable Cause and Correction on Clutch Systems
(Crouse and Anglin, 2004).
Complaint
Possible causes
Check or Correction
1. Clutch slips when
a. Incorrect clutch-linkage
Adjust
engaged.
adjustment
b. Broken or weak pressure
springs
c. Binding in clutch linkage.
Replace pressure-plate
assembly
Free, adjust, and lubricate
d. Broken engine mount.
e. Worn friction-disc facings.
Replace
f. Grease or oil disc facings.
g. Incorrectly adjusted release
Replace disc
levers.
h. Warped friction disc.
Replace disc
Adjust
Replace
2. Clutch slips while
engaged.
a. Binding in clutch linkage.
Free, adjust, and lubricate.
b. Broken engine mount.
c. Oil or grease on disc facing
Replace
or glazed or loose facings.
d. Binding of friction-disc hub
Replace disc
on clutch shaft
e. Broken disc facings,
springs, or pressure plate.
f. Warped friction disc.
Cleaning and lubricate
splines; replace defective
parts.
Replace broken parts.
Replace.
23
Table 4.1 List of Troubles, Probable….(Continued)
Complaint
3. Clutch spins or drags
while disengaged.
Possible causes
Check or Correction
a. Incorrect linkage
Adjust, repair or replace
adjustment or operation
b. Warped friction disc or
pressure plate.
Replace defective part
c. Loose friction-disc facing
d. Improper release-lever
Replace disc
adjustment
e. Friction-disc hub binding
Adjust
on clutch shaft
f. Broken engine mount
Clean and lubricate splines;
replace defective parts
Replace
4. Clutch noisy while
engaged
a. Friction-disc hub loose
Replace worn parts
on clutch shaft
b. Friction-disc dampener
springs broken or weak
Replace disc
c. Misalignment of engine
and transmission
Align
5. Clutch noisy while
disengaged
a. Release bearing worn,
Replace
binding, or out of
lubricant
b. Release levers not
properly adjusted
c. Pilot bearing in
Adjust or replace pressureplate assembly
Lubricate or replace
crankshaft worn or out of
lubricant
d. Diaphragm spring worn
or damaged
Replace pressure-plate
assembly
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Table 4.1 List of Troubles, Probable….(Continued)
Complaint
6. Clutch-pedal pulsates
Possible causes
a. Engine and transmission not
Check or Correction
Align
aligned
b. Flywheel not seated on
crankshaft flange or flywheel
Seat properly, straighten, replace
bent (also cause engine
flywheel
vibration)
c. Clutch housing distorted
d. Release levers not evenly
adjusted
Align or replace
e. Warped pressure plate or
f.
friction disc
Adjust or replace pressure-plate
Pressure-plate assembly
assembly
misaligned
Replace
g. Broken diaphragm spring
Align
Replace pressure-plate assembly
7. Rapid friction-disc
a. Driver “rides’ clutch
facing wear
Keep foot off clutch except when
necessary
b. Excessive and incorrect use of
Reduce use
clutch
c. Cranks in flywheel or pressure-
Replace
plate face
d. Weak or broken pressure
springs
Replace pressure-plate assembly
Replace defective part
e. Warped pressure-plate or
friction-disc
f.
Adjust
Improper linkage adjustment
g. Clutch linkage binding
Free, adjust, and lubricate
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Table 4.1 List of Troubles, Probable….(Continued)
Complaint
8. Clutch pedal stiff
Possible causes
a. Clutch linkage lacks
Check or Correction
Lubricate
lubricant
b. Clutch pedal binds in
Free
floor mat
c. Misaligned linkage
Align
parts
d. Over-center spring
Adjust
out or adjustment
9. Hydraulic-clutch
troubles
e. Bent clutch pedal
Replace
a. Hydraulic clutches
Inspect hydraulic system;
can have any of the
check for leakage
troubles listed above
b. Gear clashing and
difficulty shifting into
Inspect hydraulic system;
or out of gear
Check for leakage
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Assessment Task 4
A. Identify and discuss the three functions of the clutch safety switch.
1.
2.
3.
B. Provide the diagnosis and solutions for the following troubles
Complaint
1. Rapid friction-disc facing wear
Possible causes
Check or Correction
.
2. Clutch-pedal pulsates
3. Hydraulic-clutch troubles
4. Clutch noisy while engaged
5. Clutch noisy while disengaged
6. Clutch slips when engaged.
7. Clutch pedal stiff
8. Clutch slips while engaged
9. Clutch spins or drags while
disengaged.
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Summary

When the driver depresses the clutch pedal, the clutch linkage moves the release
bearing or throw-out bearing.

The type of clutch linkage determines the type of release bearing. Most are ball
bearings, but they vary in construction and operation.

Depressing the clutch pedal forces the release bearing against release levers. This
starts the release bearing rotating.

Release bearings used with self-adjusting clutches (cable and hydraulic linkage).
These require a slight preload.

Many vehicles with a clutch have a clutch safety switch or starter-clutch interlock
switch. It prevents cranking if the clutch is engaged.

The clutch safety switch prevents starting with the transmission in gear and the clutch
engaged.

Many different troubles can develop in the clutch, producing various conditions and
complaints from the driver.

For proper operation of the clutch and transmission, their common centerline must be
maintained.
References
Crouse, W. and Anglin, D. (2004). Automotive Mechanics 10th Edition, International Edition.
Sclar, Deanna. (n.d.) . Auto Repair For Dummies: Troubleshooting the Clutch on a Manual
Transmission Vehicle. 2nd Edition. Retrieved from: https://www.dummies.com/homegarden/car-repair/transmission-repair/troubleshooting-the-clutch-on-a-manualtransmission-vehicle/
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