1983 FIAT UNO compression ratio

separately, after the ten main bolts (see
Fig. 13.13).
Piston rings
14The piston rings comprise two
compression rings marked TOP, and an oil
control ring.
15Cross-sections and fitting details are
shown in Fig. 13.14.
Engine mountings - renewal
16The operations are essentially as
described in Section 33 of Chapter 1, but note
the design and fixings of the individual
mountings used on the turbocharged engine
(photos).
Timing belt - renewal#
17The operations described in Chapter 1,
Section 28 generally apply, but the following
differences should be noted.18Remove the engine compartment
right-hand shield. This is secured by plastic
clips. To remove a clip, push out its centre
pin.
19The TDC sensor must be unbolted to
provide room to remove and refit the timing
belt, which can be carried out without
having to remove the crankshaft pulley
(photos).
20The belt tensioner on later versions
does not incorporate a spring, but is of
eccentric centre bolt hole type. Have the
pulley bolt released, and tension the belt by
turning the pulley using a pin wrench or
circlip pliers in the two holes provided.
Keep the tension applied while the lockbolt
is tightened. Turn the crankshaft through
two complete turns, and then check the belt
tension. With moderate finger and thumb
pressure, the belt should just twist through90º when gripped at the mid-point of its
longest run (photo). Note: This procedure
serves only as a rough guide to setting the
belt tension - having it checked by a FIAT
dealer at the earliest opportunity is
recommended.
Oil pump drivegear cover plate
21Due to the fact that the distributor is
driven from the end of the camshaft, the oil
pump gear does not have an extension to
drive the distributor, which would be the case
if it was mounted on the crankcase.
22The crankcase aperture is therefore
covered by a plate and gasket, together with a
wiring clip (photo).
Supplement: Revisions and information on later models 13•35
6B.13 Two of the four additional cylinder
head bolts (arrowed)
Fig. 13.14 Piston ring arrangement on the
1301 cc Turbo ie engine (Sec 6B)Fig. 13.13 Cylinder head bolt tightening
sequence on the 1301 cc Turbo ie engine
(Sec 6B)
6B.22 Distributor drive hole cover plate
(arrowed)6B.20 Belt tensioner pulley locknut
(arrowed)6B.19B Removing the timing belt
6B.19A Removing the TDC sensor6B.16B Engine/transmission right-hand
mounting6B.16A Engine/transmission centre
mounting
13

Initial start-up after major
overhaul
28Refer to Chapter 1, Section 45, but note
that an oil pressure gauge is fitted to indicate
oil pressure.
29Check the ignition static timing as
described in Section 10.
30Check the engine idle speed and CO level
as described in Section 9.
7 Engine-
1372 cc ie and 1372 cc
Turbo ie
PART A: GENERAL
Description
1The 1372 cc engine is similar in design to
the OHC engine fitted to the FIAT Tipo
variants. The engine is of four-cylinder, in-line,
overhead camshaft type, mounted
transversely at the front of the vehicle.
2The crankshaft runs in five main bearings.
Thrustwashers are fitted to the rear (flywheel
end) main bearing in order to control
crankshaft endfloat.
3The connecting rods are attached to the
crankshaft by horizontally split shell-type
big-end bearings. The pistons are attached to
the connecting rods by fully-floating gudgeon
pins which are secured by circlips. The
aluminium alloy pistons are fitted with three
piston rings: two compression rings and an oil
control ring.
4The camshaft is driven by a toothed belt
and operates the valves via bucket and shim
type cam followers. The camshaft is located in
a separate housing on top of the cylinder
head.
5The inlet and exhaust valves are each
closed by double valve springs, and operate
in guides pressed into the cylinder head.
6The auxiliary shaft, which is also driven by
the toothed belt, drives the oil pump.
7Lubrication is by means of a gear type
pump which draws oil through a strainer
located in the sump, and forces it through a
full-flow filter into the engine oil galleries fromwhere it is distributed to the crankshaft,
camshaft and auxiliary shaft. The big-end
bearings are supplied with oil via internal
drillings in the crankshaft. The undersides of
the pistons are cooled by oil spray nozzles
located in each main bearing location in the
crankcase.
8A crankcase ventilation system is
employed, whereby piston blow-by gases are
drawn via an oil separator into the air cleaner,
from where they are drawn into the inlet
manifold and re-burnt with fresh air/fuel
mixture.
9The 1372 cc ie engine is fitted with a Bosch
Mono-Jetronic single point fuel injection (SPi)
system. Whilst the higher performance
1372 cc Turbo ie engine is fitted with a Bosch
L3.1 (L3.2 from 1992) Jetronic multi-point
injection (MPi) system and turbocharger with
intercooler and oil cooling. The L3.2 system
models are fitted with catalytic converters.
Maintenanceª
10At the intervals specified in Section 3 or
“Routine maintenance” at the beginning of
this Manual, carry out the following tasks.
11Check the engine oil level as follows. With
the vehicle parked on level ground, and with
the engine having been stopped for a few
minutes, withdraw the oil level dipstick, wipe it
on a clean rag, and re-insert it fully. Withdraw
the dipstick again and read off the oil level
relative to the MAX and MIN marks. The oil
level should be between the marks. If the level
is at or below the MIN mark, top up through
the filler on the camshaft cover without delay
(photo). The quantity of oil required to raise
the level from MIN to MAX on the dipstick is
approximately 1.0 litre (1.8 pints). Do not
overfill.
12Renew the engine oil and filter as
described in Section 2 of Chapter 1 (photos).
13Check and if necessary adjust the valve
clearances as described in Part B of this
Section.
14Inspect the engine for signs of oil, coolant
or fuel leaks and rectify as necessary.
15Inspect the crankcase ventilation hose for
blockage or damage. Clean or renew as
necessary.
16Check the condition and tension of thetiming belt as described in Part B of this
Section.
17Renew the timing belt as described in
Part B of this Section.
PART B:
OPERATIONS POSSlBLE
WITH ENGINE IN CAR
Valve clearances -
checking and adjustment#
1It is important to ensure that the valve
clearances are set correctly, as incorrect
clearances will result in incorrect valve timing
thus affecting engine performance.
2The clearances must be checked and
adjusted with the engine cold.
3On the ie engine, refer to Section 9 in this
Chapter for details and remove the air cleaner
unit.
4On the ie engine disconnect the crankcase
ventilation hose from the injector unit and
position the hose out of the way.
5On Turbo ie engines, loosen off the clips
and remove the air hose to the inlet manifold
(above the camshaft cover).
6On Turbo ie engines, disconnect the
accelerator cable from the throttle housing
and the support bracket on the camshaft
cover.
7Unscrew the securing nuts and washers
and remove the camshaft cover, noting that
on later models two of the nuts also secure
the hose clip assembly. Recover the gasket.
8Numbering from the front (timing belt) end
of the engine, the exhaust valves are 1, 4, 5
and 8, and the inlet valves are 2, 3, 6 and 7.
Supplement: Revisions and information on later models 13•37
7A.12B Engine oil filter removal using a
strap wrench - 1372 cc engine7A.12A Engine sump drain plug - 1372 cc
engine7A.11 Topping up the engine oil level -
1372 cc engine
Fig. 13.15 Engine oil level dipstick location
and level markings on the 1372 cc ie and
Turbo ie engines (Sec 7A)
13

necessary renovated as described later in this
Section.
191Commence refitting as follows.
192Clean the backs of the bearing shells and
the recesses in the connecting rods and
big-end caps.
193Lubricate the cylinder bores with engine
oil.
194Fit a ring compressor to No. 1 piston, theninsert the piston and connecting rod into No. 1
cylinder. With No 1 crankpin at its lowest point,
drive the piston carefully into the cylinder with
the wooden handle of a hammer (photos).
Leave enough space between the connecting
rod and the crankshaft to allow the bearing
shell to be fitted. The piston must be fitted with
the cut-out in the piston crown on the auxiliary
shaft side of the engine, and the cylinder identi-
fication marking on the connecting rod and
big-end cap on the coolant pump side of the
engine - see Fig. 13.21.
195Slide the appropriate bearing shell into
position in the connecting rod big-end, then
pull the connecting rod firmly into position on
the crankpin (photo).
196Press the appropriate bearing shell into
position in the big-end cap (photo).
197Oil the crankpin, then fit the big-end
bearing cap with the cylinder identification
marking on the coolant pump side of the
engine, and tighten the nuts to the specified
torque setting (photos).
198Check that the crankshaft turns freely.
199Repeat the procedure in paragraphs 194
to 198 inclusive on the remaining pistons.
200Refit the cylinder head and the sump.
Pistons/connecting rods -
examination and
renovation
#
201The procedures for inspecting and
renovating the pistons and connecting rod
assemblies are in general the same as thatdescribed for the smaller engines in Sec-
tion 18 of Chapter 1. However, the following
additional points should be noted.
202When renewing a gudgeon pin, first
check the fit in the piston. It should be
possible to fit the gudgeon pin using hand
pressure, but the pin should be a tight enough
fit that it does not drop out under its own
weight. Oversize gudgeon pins are available
as spares if necessary. Use new circlips when
refitting the pistons to the connecting rods.
203Before fitting the pistons to their
connecting rods, weigh each piston and
check that their weights are all within 2.5 g of
each other. If not, the heavier pistons must be
lightened by machining metal from the
underside of the small-end bosses. This
operation must be entrusted to a FIAT dealer
or engine reconditioning specialist.
204The pistons should be fitted to the
connecting rods so that the higher, flat side of
the piston crown is on the side of the
connecting rod with the stamped cylinder
identification number, ie the gudgeon pin is
offset towards the cylinder identification
number see Fig. 13.21.
205The piston rings should be fitted with the
word “TOP” on each ring facing uppermost,
or if no marks are visible, as noted during
removal. If a stepped top compression ring is
being fitted, fit the ring with the smaller
diameter of the step uppermost. The ring end
gaps should be offset 120º from each other.
Use two or three old feeler gauges to assist
13•48 Supplement: Revisions and information on later models
7B.197B . . . and tighten the nuts to the
specified torque
Fig. 13.21 Correct orientation of piston
and connecting rod in engine - 1372 cc ie
and Turbo ie engines (Sec 7B)
1 Auxiliary shaft
2 Cylinder identification markings on
connecting rod and big-end cap
Arrow denotes direction of engine rotation
Note offset gudgeon pin
7B.197A . . . then fit the cap . . .7B.196 . . . and big-end bearing cap . . .
7B.195 Assemble the shell bearing to the
connecting rod . . .7B.194B Tapping a piston into its bore7B.194A Fitting a ring compressor to a
piston

fitting, as during removal. Note that the
compression rings are brittle, and will snap if
expanded too far.
206If new pistons are to be fitted, they must
be selected from the grades available, after
measuring the cylinder bores. Normally, the
appropriate oversize pistons are supplied by
the dealer when the block is rebored.
207Whenever new piston rings are being
installed, the glaze on the original cylinder
bores should be removed using either
abrasive paper or a glaze-removing tool in an
electric drill. If abrasive paper is used, use
strokes at 60º to the bore centre-line, to
create a cross-hatching effect.
Engine/transmission
mountings - renewalÁ
208The engine/gearbox assembly is
suspended in the engine compartment on
three mountings, two of which are attached to
the gearbox, and one to the engine.
Right-hand mounting
209Apply the handbrake, then jack up the
front of the vehicle and support it securely on
axle stands.
210Suitable lifting tackle must now be
attached to the engine in order to support it as
the engine mounting is removed. No lifting
brackets are provided, so care must be taken
when deciding on an engine lifting point. In the
workshop, a right-angled bracket was made up
by bending a suitable piece of steel plate. The
bracket was then bolted to the engine using the
rear right-hand camshaft housing securing bolt
with suitable packing washers.
211Attach the lifting tackle to the bracket on
the engine and just take the weight of the
assembly.
212Working under the vehicle, unbolt the
engine mounting bracket from the cylinder
block, and unbolt the mounting from the
body, then withdraw the bracket/mounting
assembly.
213Unscrew the nut and through-bolt,
counter holding the bolt with a second
spanner or socket, and separate the mounting
from the bracket.
214Fit the new mounting to the bracket, and
tighten the nut to the specified torque, while
counterholding the through-bolt using a
suitable spanner or socket.
215Refit the mounting bracket to the cylinder
block, and tighten the securing bolts to the
specified torque.
216Refit the mounting to the body and
tighten the securing bolts to the specified
torque.
217Disconnect the lifting tackle from the
engine, and remove the engine lifting bracket.
218Lower the vehicle to the ground.
Left-hand mountings
219Apply the handbrake, then jack up the
front of the vehicle and support it securely on
axle stands.
220Suitable lifting tackle must now be
attached to the gearbox lifting bracket inorder to support the weight of the assembly
as the mounting is removed.
221Attach the lifting tackle to the bracket on
the gearbox, and just take the weight of the
assembly.
222Working under the vehicle, unbolt the
mounting bracket from the gearbox, and
unbolt the mounting from the body, then
withdraw the bracket/mounting assembly.
223Proceed as described in paragraphs 213
and 214.
224Refit the mounting bracket to the
gearbox, and tighten the securing bolts to the
specified torque.
225Refit the mounting to the body and
tighten the mounting bolts to the specified
torque.
226Disconnect the lifting tackle from the
engine.
227Lower the vehicle to the ground.
PART C: ENGINE REMOVAL
AND DISMANTLING
Method of removal - general
1The engine (complete with transmission) is
disconnected and lowered downwards
through the engine compartment, then
withdrawn from the front underside of the car.
1372 cc engine/
transmission - removal
and separation
#
Warning: Refer to the beginning
of Section 9 before starting any
work.
2Depressurize the fuel system as described
in Section 9 of this Chapter.
3Disconnect the battery negative lead.
4Mark the position of the hinges on the
underside of the bonnet, then with the aid of
an assistant, unscrew the hinge bolts and lift
the bonnet clear of the car. Store the bonnet
in a safe area.
5Drain the engine coolant.
6Drain the engine and transmission oils.
7Disconnect and remove the air filter.
8Disconnect the coolant hoses from the
engine, including the hose to the inlet
manifold.
9Detach the ignition coil (HT) lead from the
distributor.10Compress the retaining clip and detach
the engine idle speed actuator lead from the
SPi unit (photo).
11Disconnect the brake servo vacuum pipe
from its connector on the inlet manifold.
12Disconnect the throttle cable from the SPi
unit.
13Disconnect the engine speed sensor lead.
14Release and detach the reversing light
lead from the switch on the transmission
(photo).
15Before disconnecting the hydraulic hose
from the clutch slave cylinder, remove the
filler cap from the reservoir and place a piece
of polythene sheet over the filler neck, then
refit the cap; this will help prevent excess fluid
loss. Once disconnected, plug the hose and
its cylinder connection to prevent the ingress
of dirt into the hydraulic system.
16Disconnect the wiring connector from the
alternator.
17Position a clean rag under the fuel supply
and return hose connections to the SPi unit,
then slowly unscrew the hose clips to release
the system pressure; catch fuel leakage in the
rag and dispose of it safely. Detach the hoses
and plug them to prevent ingress of dirt and
any further fuel leakage. Position the hoses
out of the way.
18Detach the wiring connector from the
engine coolant temperature sender unit
(photo).
19Release the retaining clip and detach the
wiring connector from the throttle position
switch. Also detach the associated earth
leads from the cylinder head.
Supplement: Revisions and information on later models 13•49
7C.14 Reversing light switch and lead7C.18 Engine coolant temperature sender
and wiring connector
7C.10 Engine idle speed actuator/SPi unit
lead connection (arrowed)
13

35Clean the mating faces of the thermostat
cover and cylinder head, and use a new
gasket when refitting the cover.
36Refill the cooling system as described
earlier in this Section.
Coolant pump -
removal and refittingÁ
Note: A new coolant pump gasket must be
used on refitting. If the pump is found to be
worn it must be renewed as a complete unit as
dismantling and repair is not possible.
37Disconnect the battery negative lead.
38Drain the cooling system as described
earlier in this Section.
39Remove the coolant/alternator drivebelt
as described in the next sub-Section.
40Unscrew the four coolant pump securing
bolts, noting that two of the bolts also secure
the alternator adjuster bracket, and withdraw
the pump from the housing (photo). Recover
the gasket.
41Refitting is a reversal of removal, bearing
in mind the following points.
42Use a new gasket between the pump and
the housing.
43Refit and tension the coolant
pump/alternator drivebelt as described in the
next sub-Section.
44On completion, refill the cooling system
as described earlier in this Section.
Coolant pump/alternator
drivebelt - checking,
renewal and tensioning
Á
45At the intervals specified in Section 3 or
“Routine maintenance” at the beginning of
this manual (as applicable), the drivebelt
should be checked and if necessary
re-tensioned.
46Access to the drivebelt is made from the
underside of the car on the right-hand side.
Loosen off the front right-hand roadwheel
retaining bolts, then raise and support the car
on axle stands at the front. Remove the front
roadwheel on the right-hand side.
47Remove the underwing shield from the
right-hand wheel arch by drifting the
compression pins out from the retaining
clips. Prise free the clips and remove the
shield.
48Additional, though somewhat restricted,
access can be obtained from above by
removing the air cleaner unit on the non-Turbo
ie-engine (photo).
49Check the full length of the drivebelt for
cracks and deterioration. It will be necessary
to turn the engine in order to check the
portions of the drivebelt in contact with the
pulleys. If a drivebelt is unserviceable, renew it
as follows (photo).
50Loosen the alternator mounting and
adjuster nuts and bolts and pivot the
alternator towards the cylinder block.51Slip the drivebelt from the alternator,
coolant pump and crankshaft pulleys.
52Fit the new drivebelt around the pulleys,
then lever the alternator away from the
cylinder block until the specified belt tension
is achieved. Lever the alternator using a
wooden or plastic lever at the pulley end to
prevent damage. It is helpful to partially
tighten the adjuster nut before tensioning the
drivebelt (photo).
53When the specified tension has been
achieved, tighten the mounting and adjuster
nuts and bolts (photo).
PART D: HEATER UNIT- LATER
MODELS
Heater unit -
removal and refitting
Á
1The heater unit is removed complete with
the facia/control panel. Commence by
draining the cooling system as described
previously in this Section.
2Disconnect the battery negative lead.
3Refer to Section 15 of this Chapter for
details and remove the ashtray/cigar lighter
and the auxiliary control panel.
4Undo the upper screw retaining the heater
unit to the facia (see Fig. 13.31).
5Remove the radio from the central facia.
6Undo the retaining screw on each side at
the front of the gear lever console. Prise free
13•58 Supplement: Revisions and information on later models
Fig. 13.31 Removing the heater unit-to-
facia upper retaining screw (Sec 8D)8C.53 Tightening the alternator adjuster
nut8C.52 Fitting a new coolant
pump/alternator drivebelt around the
pulleys
8C.49 Alternator/water pump drivebelt and
tensioner viewed from the right-hand
wheel arch8C.48 Top side view of water pump,
alternator and drivebelt8C.40 Coolant pump/alternator bracket
bolt removal

Vacuum servo unit and master
cylinder - general
54Access to the vacuum servo unit and the
master cylinder can only be obtained after the
cooling system expansion tank has been
released and moved aside (photo).
Antiskid system - description
55This system is available as an option on
the Turbo ie models only.
56The purpose of the system is to prevent
the wheel(s) locking during heavy brake
applications. This is achieved by automatic
release of the brake on a roadwheel which is
about to lock up, after which the brake is
re-applied. This cycle is carried out many
times per second under heavy braking,
retaining full steering control to avoid any
hazards.
57The main components of the system are
shown in Fig. 13.102. The control module
processes the signals received from the
sensors, and compares them with
deceleration values of the roadwheel and the
slip values of the tyre, which are stored in the
module memory.
58When reference values are exceeded and
wheel lock is imminent, the control module
signals the pressure modulators, which in turn
decrease the brake hydraulic pressure.
59Vehicle road speeds are also taken into
account by the module’s electronic circuits.
60In order to retain optimum system
performance, the tyres and wheels shouldalways be of the type originally fitted by the
vehicle manufacturer.
61Maintenance of the system should be
limited to checking the security of all electrical
and hydraulic connections. Individual compo-
nents are not repairable, and must be
renewed complete if faulty.15 Electrical system
Alternator (999 and
1108 cc models) -
removal and refitting
Á
1To remove the alternator from 999 cc
engine models, disconnect the leads from the
terminals on its rear face.
2Extract the screws and remove the plastic
drivebelt guard.
3Slacken the mounting and adjuster bolts,
push the alternator in towards the engine and
remove the drivebelt.
4Remove the mounting and adjuster bolts,
and withdraw the alternator downwards
through the gap between the right-hand
driveshaft and the engine sump pan (photo).
5Refitting is a reversal of removal; re-tension
the drivebelt.
Alternator (later models) -
removal and refitting Á
6Disconnect the battery negative lead.
7Loosen off the right-hand front roadwheelbolts, then raise and support the car at the
front end on axle stands. Remove the
right-hand roadwheel.
8Remove the wheel arch underwing shield
by driving the compression pins from the
centre of the retaining clips (using a 2 mm
drift), then prise free the panel retaining clips
and remove the shield. Keep the pins and
clips in a safe place and renew any that may
have been damaged during removal (photo).
9Detach the wiring connector from the
alternator.
10Release the alternator mounting and belt
adjuster link bolts, and take off the drivebelt.
11Take out the alternator top and bottom
mounting bolts.
Supplement: Revisions and information on later models 13•103
15.4 Removing the alternator from the
999 cc engine
Fig. 13.102 Braking system on Turbo ie Antiskid models (Sec 14)
13
1 Electronic control unit
(ECU)
2 Roadwheel speed
sensors
3 Pressure modulators
4 Vacuum reservoir
5 Check valve
6 Air cleaner
7 Load proportioning
(pressure regulating)
valves
8 Vacuum switch
9 ECU relay
10 System fault warning
lamp relay
11 System fault warning
lamp
12 Brake stop lamp
switch

Tools and Working FacilitiesREF•7
REF
MImpact screwdriver
MMicrometer and/or vernier calipers (see
illustrations)
MDial gauge (see illustration)
MUniversal electrical multi-meter
MCylinder compression gauge
(see illustration)
MClutch plate alignment set (see
illustration)
MBrake shoe steady spring cup removal tool
(see illustration)
MBush and bearing removal/installation set
(see illustration)
MStud extractors (see illustration)
MTap and die set (see illustration)
MLifting tackle
MTrolley jack
Buying tools
For practically all tools, a tool factor is the
best source, since he will have a very
comprehensive range compared with the
average garage or accessory shop. Having
said that, accessory shops often offer
excellent quality tools at discount prices, so it
pays to shop around.
Remember, you don’t have to buy the most
expensive items on the shelf, but it is always
advisable to steer clear of the very cheap
tools. There are plenty of good tools around atreasonable prices, but always aim to
purchase items which meet the relevant
national safety standards. If in doubt, ask the
proprietor or manager of the shop for advice
before making a purchase.
Care and maintenance of tools
Having purchased a reasonable tool kit, it is
necessary to keep the tools in a clean and
serviceable condition. After use, always wipe
off any dirt, grease and metal particles using a
clean, dry cloth, before putting the tools away.
Never leave them lying around after they have
been used. A simple tool rack on the garage
or workshop wall for items such as
screwdrivers and pliers is a good idea. Store
all normal spanners and sockets in a metal
box. Any measuring instruments, gauges,
meters, etc, must be carefully stored where
they cannot be damaged or become rusty.
Take a little care when tools are used.
Hammer heads inevitably become marked,
and screwdrivers lose the keen edge on their
blades from time to time. A little timely
attention with emery cloth or a file will soon
restore items like this to a good serviceable
finish.
Working facilities
Not to be forgotten when discussing toolsis the workshop itself. If anything more than
routine maintenance is to be carried out,
some form of suitable working area becomes
essential.
It is appreciated that many an owner-
mechanic is forced by circumstances to
remove an engine or similar item without the
benefit of a garage or workshop. Having done
this, any repairs should always be done under
the cover of a roof.
Wherever possible, any dismantling should
be done on a clean, flat workbench or table at
a suitable working height.
Any workbench needs a vice; one with a
jaw opening of 100 mm is suitable for most
jobs. As mentioned previously, some clean
dry storage space is also required for tools, as
well as for any lubricants, cleaning fluids,
touch-up paints and so on, which become
necessary.
Another item which may be required, and
which has a much more general usage, is an
electric drill with a chuck capacity of at least 8
mm. This, together with a good range of twist
drills, is virtually essential for fitting
accessories.
Last, but not least, always keep a supply of
old newspapers and clean, lint-free rags
available, and try to keep any working area as
clean as possible.
Bush and bearing removal/installation setStud extractor setTap and die set

REF•14Glossary of Technical Terms
Catalytic converterA silencer-like device in
the exhaust system which converts certain
pollutants in the exhaust gases into less
harmful substances.
CirclipA ring-shaped clip used to prevent
endwise movement of cylindrical parts and
shafts. An internal circlip is installed in a
groove in a housing; an external circlip fits into
a groove on the outside of a cylindrical piece
such as a shaft.
ClearanceThe amount of space between
two parts. For example, between a piston and
a cylinder, between a bearing and a journal,
etc.
Coil springA spiral of elastic steel found in
various sizes throughout a vehicle, for
example as a springing medium in the
suspension and in the valve train.
CompressionReduction in volume, and
increase in pressure and temperature, of a
gas, caused by squeezing it into a smaller
space.
Compression ratioThe relationship between
cylinder volume when the piston is at top
dead centre and cylinder volume when the
piston is at bottom dead centre.
Constant velocity (CV) jointA type of
universal joint that cancels out vibrations
caused by driving power being transmitted
through an angle.
Core plugA disc or cup-shaped metal device
inserted in a hole in a casting through which
core was removed when the casting was
formed. Also known as a freeze plug or
expansion plug.
CrankcaseThe lower part of the engine
block in which the crankshaft rotates.
CrankshaftThe main rotating member, or
shaft, running the length of the crankcase,
with offset “throws” to which the connecting
rods are attached.
Crocodile clipSee Alligator clipDDiagnostic codeCode numbers obtained by
accessing the diagnostic mode of an engine
management computer. This code can be
used to determine the area in the system
where a malfunction may be located.
Disc brakeA brake design incorporating a
rotating disc onto which brake pads are
squeezed. The resulting friction converts the
energy of a moving vehicle into heat.
Double-overhead cam (DOHC)An engine
that uses two overhead camshafts, usually
one for the intake valves and one for the
exhaust valves.
Drivebelt(s)The belt(s) used to drive
accessories such as the alternator, water
pump, power steering pump, air conditioning
compressor, etc. off the crankshaft pulley.
DriveshaftAny shaft used to transmit
motion. Commonly used when referring to the
axleshafts on a front wheel drive vehicle.
Drum brakeA type of brake using a drum-
shaped metal cylinder attached to the inner
surface of the wheel. When the brake pedal is
pressed, curved brake shoes with friction
linings press against the inside of the drum to
slow or stop the vehicle.
EEGR valveA valve used to introduce exhaust
gases into the intake air stream.
Electronic control unit (ECU)A computer
which controls (for instance) ignition and fuel
injection systems, or an anti-lock braking
system. For more information refer to the
Haynes Automotive Electrical and Electronic
Systems Manual.
Electronic Fuel Injection (EFI)A computer
controlled fuel system that distributes fuel
through an injector located in each intake port
of the engine.
Emergency brakeA braking system,
independent of the main hydraulic system,
that can be used to slow or stop the vehicle if
the primary brakes fail, or to hold the vehicle
stationary even though the brake pedal isn’t
depressed. It usually consists of a hand lever
that actuates either front or rear brakes
mechanically through a series of cables and
linkages. Also known as a handbrake or
parking brake.EndfloatThe amount of lengthwise
movement between two parts. As applied to a
crankshaft, the distance that the crankshaft
can move forward and back in the cylinder
block.
Engine management system (EMS)A
computer controlled system which manages
the fuel injection and the ignition systems in
an integrated fashion.
Exhaust manifoldA part with several
passages through which exhaust gases leave
the engine combustion chambers and enter
the exhaust pipe.
F
Fan clutchA viscous (fluid) drive coupling
device which permits variable engine fan
speeds in relation to engine speeds.
Feeler bladeA thin strip or blade of hardened
steel, ground to an exact thickness, used to
check or measure clearances between parts.
Firing orderThe order in which the engine
cylinders fire, or deliver their power strokes,
beginning with the number one cylinder.
Flywheel A heavy spinning wheel in which
energy is absorbed and stored by means of
momentum. On cars, the flywheel is attached
to the crankshaft to smooth out firing
impulses.
Free playThe amount of travel before any
action takes place. The “looseness” in a
linkage, or an assembly of parts, between the
initial application of force and actual
movement. For example, the distance the
brake pedal moves before the pistons in the
master cylinder are actuated.
FuseAn electrical device which protects a
circuit against accidental overload. The typical
fuse contains a soft piece of metal which is
calibrated to melt at a predetermined current
flow (expressed as amps) and break the
circuit.
Fusible linkA circuit protection device
consisting of a conductor surrounded by
heat-resistant insulation. The conductor is
smaller than the wire it protects, so it acts as
the weakest link in the circuit. Unlike a blown
fuse, a failed fusible link must frequently be
cut from the wire for replacement.Catalytic converter
Crankshaft assembly
Accessory drivebelts
Feeler blade