Peugeot 405 Haynes (petrol). Manual - part 37

7 Driveshafts

5 Manual transmission

REF•16

Fault Finding

Noisy in neutral with engine running

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Primary gears and bearings worn (noise apparent with clutch
pedal released, but not when depressed) (Chapter 7A).*

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Clutch release bearing worn (noise apparent with clutch pedal
depressed, possibly less when released) (Chapter 6).

Noisy in one particular gear

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Worn, damaged or chipped gear teeth (Chapter 7A).*

Difficulty engaging gears

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Clutch fault (Chapter 6).

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Worn or damaged gear linkage (Chapter 7A).

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Incorrectly-adjusted gear linkage (Chapter 7A).

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Worn synchroniser units (Chapter 7A).*

Jumps out of gear

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Worn or damaged gear linkage (Chapter 7A).

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Incorrectly-adjusted gear linkage (Chapter 7A).

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Worn synchroniser units (Chapter 7A).*

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Worn selector forks (Chapter 7A).*

Vibration

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Lack of oil (Chapter 1).

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Worn bearings (Chapter 7A).*

Lubricant leaks

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Leaking differential output oil seal (Chapter 7A).

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Leaking housing joint (Chapter 7A).*

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Leaking input shaft oil seal (Chapter 7A).*

*Although the corrective action necessary to remedy the symptoms
described is beyond the scope of the home mechanic, the above
information should be helpful in isolating the cause of the condition,
so that the owner can communicate clearly with a professional
mechanic.

6 Automatic transmission

Note: Due to the complexity of the automatic transmission, it is
difficult for the home mechanic to properly diagnose and service this
unit. For problems other than the following, the vehicle should be
taken to a dealer service department or automatic transmission
specialist.

Fluid leakage

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Automatic transmission fluid is usually deep red in colour. Fluid
leaks should not be confused with engine oil, which can easily
be blown onto the transmission by air flow.

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To determine the source of a leak, first remove all built-up dirt
and grime from the transmission housing and surrounding areas,
using a degreasing agent or by steam-cleaning. Drive the vehicle
at low speed, so that air flow will not blow the leak far from its
source. Raise and support the vehicle, and determine where the
leak is coming from. The following are common areas of leakage.

a) Fluid pan (Chapter 1 and 7B).
b) Dipstick tube (Chapter 1 and 7B).
c) Transmission-to-fluid cooler fluid pipes/unions (Chapter 7B).

Transmission fluid brown, or has burned smell

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Transmission fluid level low, or fluid in need of renewal 
(Chapter 1).

General gear selection problems

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Chapter 7B deals with checking and adjusting the selector cable
on automatic transmissions. The following are common
problems which may be caused by a poorly-adjusted cable:

a) Engine starting in gears other than Park or Neutral.
b) Indicator on gear selector lever pointing to a gear other than the

one actually being used.

c) Vehicle moves when in Park or Neutral.
d) Poor gear shift quality, or erratic gear changes.

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Refer to Chapter 7B for the selector cable adjustment procedure.

Transmission will not downshift (kickdown) 
with accelerator pedal fully depressed

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Low transmission fluid level (Chapter 1).

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Incorrect selector cable adjustment (Chapter 7B).

Engine will not start in any gear, 
or starts in gears other than Park or Neutral

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Incorrect starter/inhibitor switch adjustment - where applicable
(Chapter 7B).

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Incorrect selector cable adjustment (Chapter 7B).

Transmission slips, shifts roughly, is noisy, 
or has no drive in forward or reverse gears

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There are many probable causes for the above problems, but the
home mechanic should be concerned with only one possibility -
fluid level. Before taking the vehicle to a dealer or transmission
specialist, check the fluid level and condition of the fluid as
described in Chapter 1. Correct the fluid level as necessary, or
change the fluid and filter if needed. If the problem persists,
professional help will be necessary.

Clicking or knocking noise on turns 
(at slow speed on full-lock)

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Lack of constant velocity joint lubricant, possibly due to
damaged gaiter (Chapter 8).

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Worn outer constant velocity joint (Chapter 8).

Vibration when accelerating or decelerating

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Worn inner constant velocity joint (Chapter 8).

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Bent or distorted driveshaft (Chapter 8).

Fault Finding

REF•17

REF

8 Braking system

Note: Before assuming that a brake problem exists, make sure that
the tyres are in good condition and correctly inflated, that the front
wheel alignment is correct, and that the vehicle is not loaded with
weight in an unequal manner.

Vehicle pulls to one side under braking

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Worn, defective, damaged or contaminated front or rear brake
pads/shoes on one side (Chapters 1 and 9).

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Seized or partially-seized brake caliper/wheel cylinder piston
(Chapter 9).

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A mixture of brake pad/shoe lining materials fitted between sides
(Chapter 9).

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Brake caliper mounting bolts loose (Chapter 9).

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Worn or damaged steering or suspension components 
(Chapters 1 and 10).

Noise (grinding or high-pitched squeal) 
when brakes applied

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Brake pad/shoe friction lining material worn down to metal
backing (Chapters 1 and 9).

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Excessive corrosion of brake disc/drum - may be apparent after
the vehicle has been standing for some time (Chapters 1 and 9).

Excessive brake pedal travel

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Faulty master cylinder (Chapter 9).

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Air in hydraulic system (Chapter 9).

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Faulty vacuum servo unit (Chapter 9).

Brake pedal feels spongy when depressed

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Air in hydraulic system (Chapter 9).

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Deteriorated flexible rubber brake hoses (Chapters 1 and 9).

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Master cylinder mountings loose (Chapter 9).

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Faulty master cylinder (Chapter 9).

Excessive brake pedal effort 
required to stop vehicle

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Faulty vacuum servo unit (Chapter 9).

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Disconnected, damaged or insecure brake servo vacuum hose
(Chapters 1 and 9).

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Primary or secondary hydraulic circuit failure (Chapter 9).

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Seized brake caliper/wheel cylinder piston(s) (Chapter 9).

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Brake pads/shoes incorrectly fitted (Chapter 9).

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Incorrect grade of brake pads/shoes fitted (Chapter 9).

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Brake pads/shoes contaminated (Chapter 9).

Judder felt through brake pedal or 
steering wheel when braking

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Excessive run-out or distortion of brake disc/drum (Chapter 9).

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Brake pad/shoe linings worn (Chapters 1 and 9).

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Brake caliper mounting bolts loose (Chapter 9).

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Wear in suspension or steering components or mountings
(Chapters 1 and 10).

Brakes binding

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Seized brake caliper/wheel cylinder piston(s) (Chapter 9).

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Incorrectly-adjusted handbrake mechanism (Chapter 9).

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Faulty master cylinder (Chapter 9).

Rear wheels locking under normal braking

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Seized brake caliper/wheel cylinder piston(s) (Chapter 9).

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Faulty brake pressure regulator (Chapter 9).

9 Suspension and steering

Note: Before diagnosing suspension or steering faults, be sure that
the trouble is not due to incorrect tyre pressures, mixtures of tyre
types, or binding brakes.

Vehicle pulls to one side

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Defective tyre (Chapter 1).

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Excessive wear in suspension or steering components 
(Chapters 1 and 10).

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Incorrect front wheel alignment (Chapter 10).

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Accident damage to steering or suspension components
(Chapters 1 and 10).

Wheel wobble and vibration

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Front roadwheels out of balance (vibration felt mainly through
the steering wheel) (Chapter 10).

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Rear roadwheels out of balance (vibration felt throughout the
vehicle) (Chapter 10).

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Roadwheels damaged or distorted (Chapter 10).

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Faulty or damaged tyre (Chapter 1).

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Worn steering or suspension joints, bushes or components
(Chapters 1 and 10).

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Wheel nuts loose (Chapter 10).

Excessive pitching and/or rolling around
corners, or during braking

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Defective shock absorbers (Chapters 1 and 10).

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Broken or weak coil spring and/or suspension component
(Chapters 1 and 10).

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Worn or damaged anti-roll bar or mountings (Chapter 10).

Wandering or general instability

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Incorrect front wheel alignment (Chapter 10).

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Worn steering or suspension joints, bushes or components
(Chapters 1 and 10).

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Roadwheels out of balance (Chapter 10).

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Faulty or damaged tyre (“Weekly checks”).

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Wheel nuts loose (Chapter 10).

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Defective shock absorbers (Chapters 1 and 10).

Excessively-stiff steering

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Lack of steering gear lubricant (Chapter 10).

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Seized track rod end or suspension balljoint (Chapters 1 and 10).

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Broken or incorrectly adjusted auxiliary drivebelt (Chapter 1).

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Incorrect front wheel alignment (Chapter 10).

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Steering rack or column bent or damaged (Chapter 10).

Excessive play in steering

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Worn steering column universal joint(s) (Chapter 10).

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Worn steering track rod end balljoints (Chapters 1 and 10).

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Worn rack-and-pinion steering gear (Chapter 10).

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Worn steering or suspension joints, bushes or components
(Chapters 1 and 10).

Lack of power assistance

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Broken or incorrectly-adjusted auxiliary drivebelt (Chapter 1).

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Incorrect power steering fluid level (“Weekly checks”).

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Restriction in power steering fluid hoses (Chapter 1).

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Faulty power steering pump (Chapter 10).

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Faulty rack-and-pinion steering gear (Chapter 10).

9 Suspension and steering (continued)

REF•18

Fault Finding

Tyre wear excessive

Tyres worn on inside or outside edges

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Tyres under-inflated (wear on both edges) (“Weekly checks”).

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Incorrect camber or castor angles (wear on one edge only)
(Chapter 10).

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Worn steering or suspension joints, bushes or components
(Chapters 1 and 10).

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Excessively-hard cornering.

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Accident damage.

Tyre treads exhibit feathered edges

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Incorrect toe setting (Chapter 10).

Tyres worn in centre of tread

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Tyres over-inflated (“Weekly checks”).

Tyres worn on inside and outside edges

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Tyres under-inflated (“Weekly checks”).

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Worn shock absorbers (Chapters 1 and 10).

Tyres worn unevenly

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Tyres out of balance (Chapter 1).

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Excessive wheel or tyre run-out (Chapter 1).

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Worn shock absorbers (Chapters 1 and 10).

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Faulty tyre (“Weekly checks”).

10 Electrical system

Note: For problems associated with the starting system, refer to the faults listed under “Engine” earlier in this Section.

Battery will not hold a charge 
for more than a few days

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Battery defective internally (Chapter 5).

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Battery electrolyte level low - where applicable 
(“Weekly checks”).

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Battery terminal connections loose or corroded 
(“Weekly checks”).

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Auxiliary drivebelt worn - or incorrectly adjusted (Chapter 1).

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Alternator not charging at correct output (Chapter 5).

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Alternator or voltage regulator faulty (Chapter 5).

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Short-circuit causing continual battery drain (Chapters 5 and 12).

Ignition/no-charge warning light remains
illuminated with engine running

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Auxiliary drivebelt broken, worn, or incorrectly adjusted 
(Chapter 1).

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Alternator brushes worn, sticking, or dirty (Chapter 5).

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Alternator brush springs weak or broken (Chapter 5).

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Internal fault in alternator or voltage regulator (Chapter 5).

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Broken, disconnected, or loose wiring in charging circuit
(Chapter 5).

Ignition/no-charge warning light fails to come on

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Warning light bulb blown (“Weekly checks”).

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Broken, disconnected, or loose wiring in warning light circuit
(Chapter 12).

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Alternator faulty (Chapter 5).

Lights inoperative

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Bulb blown (Chapter 12).

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Corrosion of bulb or bulbholder contacts (Chapter 12).

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Blown fuse (Chapter 12).

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Faulty relay (Chapter 12).

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Broken, loose, or disconnected wiring (Chapter 12).

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Faulty switch (Chapter 12).

Instrument readings inaccurate or erratic

Instrument readings increase with engine speed

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Faulty voltage regulator (Chapter 12).

Fuel or temperature gauges give no reading

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Faulty gauge sender unit (Chapters 3 and 4A or 4B).

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Wiring open-circuit (Chapter 12).

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Faulty gauge (Chapter 12).

Fuel or temperature gauges 
give continuous maximum reading

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Faulty gauge sender unit (Chapters 3 and 4A or 4B).

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Wiring short-circuit (Chapter 12).

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Faulty gauge (Chapter 12).

Horn inoperative, or unsatisfactory in operation

Horn operates all the time

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Horn contacts permanently bridged or horn push stuck down
(Chapter 12).

Horn fails to operate

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Blown fuse (Chapter 12).

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Cable or cable connections loose, broken or disconnected
(Chapter 12).

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Faulty horn (Chapter 12).

Horn emits intermittent or unsatisfactory sound

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Cable connections loose (Chapter 12).

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Horn mountings loose (Chapter 12).

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Faulty horn (Chapter 12).

Windscreen/tailgate wipers inoperative, or
unsatisfactory in operation

Wipers fail to operate, or operate very slowly

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Wiper blades stuck to screen, or linkage seized or binding
(Chapters 1 and 12).

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Blown fuse (Chapter 12).

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Cable or cable connections loose, broken or disconnected
(Chapter 12).

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Faulty relay (Chapter 12).

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Faulty wiper motor (Chapter 12).

Wiper blades sweep over 
too large or too small an area of the glass

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Wiper arms incorrectly positioned on spindles (Chapter 1).

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Excessive wear of wiper linkage (Chapter 12).

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Wiper motor or linkage mountings loose or insecure 
(Chapter 12).

Wiper blades fail to clean the glass effectively

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Wiper blade rubbers worn or perished (“Weekly checks”).

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Wiper arm tension springs broken, or arm pivots seized 
(Chapter 12).

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Insufficient windscreen washer additive to adequately remove
road film (“Weekly checks”).

Windscreen/tailgate washers inoperative, 
or unsatisfactory in operation

One or more washer jets inoperative

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Blocked washer jet (Chapter 1).

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Disconnected, kinked or restricted fluid hose (Chapter 12).

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Insufficient fluid in washer reservoir (“Weekly checks”).

Washer pump fails to operate

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Broken or disconnected wiring or connections (Chapter 12).

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Blown fuse (Chapter 12).

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Faulty washer switch (Chapter 12).

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Faulty washer pump (Chapter 12).

Washer pump runs for some time 
before fluid is emitted from jets

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Faulty one-way valve in fluid supply hose (Chapter 12).

Electric windows inoperative, 
or unsatisfactory in operation

Window glass will only move in one direction

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Faulty switch (Chapter 12).

Window glass slow to move

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Regulator seized or damaged, or in need of lubrication 
(Chapter 11).

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Door internal components or trim fouling regulator (Chapter 11).

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Faulty motor (Chapter 11).

Window glass fails to move

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Blown fuse (Chapter 12).

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Faulty relay (Chapter 12).

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Broken or disconnected wiring or connections (Chapter 12).

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Faulty motor (Chapter 11).

Central locking system inoperative, 
or unsatisfactory in operation

Complete system failure

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Blown fuse (Chapter 12).

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Faulty relay (Chapter 12).

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Broken or disconnected wiring or connections (Chapter 12).

Latch locks but will not unlock, 
or unlocks but will not lock

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Faulty switch (Chapter 12).

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Broken or disconnected latch operating rods or levers 
(Chapter 11).

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Faulty relay (Chapter 12).

One solenoid/motor fails to operate

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Broken or disconnected wiring or connections (Chapter 12).

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Faulty solenoid/motor (Chapter 11).

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Broken, binding or disconnected latch operating rods or levers
(Chapter 11).

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Fault in door latch (Chapter 11).

Fault Finding

REF•19

REF

REF•20

Glossary of Technical Terms

A

ABS (Anti-lock brake system)

A system,

usually electronically controlled, that senses
incipient wheel lockup during braking and
relieves hydraulic pressure at wheels that are
about to skid.
Air bag  An inflatable bag hidden in the
steering wheel (driver’s side) or the dash or
glovebox (passenger side). In a head-on
collision, the bags inflate, preventing the
driver and front passenger from being thrown
forward into the steering wheel or windscreen.
Air cleaner

A metal or plastic housing,

containing a filter element, which removes
dust and dirt from the air being drawn into the
engine.
Air filter element The actual filter in an air
cleaner system, usually manufactured from
pleated paper and requiring renewal at regular
intervals.

Allen key A hexagonal wrench which fits into
a recessed hexagonal hole.
Alligator clip

A long-nosed spring-loaded

metal clip with meshing teeth. Used to make
temporary electrical connections.
Alternator

A component in the electrical

system which converts mechanical energy
from a drivebelt into electrical energy to
charge the battery and to operate the starting
system, ignition system and electrical
accessories. 

Ampere (amp) A unit of measurement for the
flow of electric current. One amp is the
amount of current produced by one volt
acting through a resistance of one ohm.
Anaerobic sealer

A substance used to

prevent bolts and screws from loosening.
Anaerobic means that it does not require
oxygen for activation. The Loctite brand is
widely used.
Antifreeze

A substance (usually ethylene

glycol) mixed with water, and added to a
vehicle’s cooling system, to prevent freezing
of the coolant in winter. Antifreeze also
contains chemicals to inhibit corrosion and
the formation of rust and other deposits that

would tend to clog the radiator and coolant
passages and reduce cooling efficiency.
Anti-seize compound

A coating that

reduces the risk of seizing on fasteners that
are subjected to high temperatures, such as
exhaust manifold bolts and nuts.

Asbestos A natural fibrous mineral with great
heat resistance, commonly used in the
composition of brake friction materials.
Asbestos is a health hazard and the dust
created by brake systems should never be
inhaled or ingested.
Axle A shaft on which a wheel revolves, or
which revolves with a wheel. Also, a solid
beam that connects the two wheels at one
end of the vehicle. An axle which also
transmits power to the wheels is known as a
live axle.

Axleshaft

A single rotating shaft, on either

side of the differential, which delivers power
from the final drive assembly to the drive
wheels. Also called a driveshaft or a halfshaft.

B

Ball bearing

An anti-friction bearing

consisting of a hardened inner and outer race
with hardened steel balls between two races.

Bearing The curved surface on a shaft or in a
bore, or the part assembled into either, that
permits relative motion between them with
minimum wear and friction.
Big-end bearing The bearing in the end of
the connecting rod that’s attached to the
crankshaft.
Bleed nipple

A valve on a brake wheel

cylinder, caliper or other hydraulic component
that is opened to purge the hydraulic system
of air. Also called a bleed screw.

Brake bleeding Procedure for removing air
from lines of a hydraulic brake system.
Brake disc The component of a disc brake
that rotates with the wheels.
Brake drum The component of a drum brake
that rotates with the wheels.
Brake linings

The friction material which

contacts the brake disc or drum to retard the
vehicle’s speed. The linings are bonded or
riveted to the brake pads or shoes.
Brake pads

The replaceable friction pads

that pinch the brake disc when the brakes are
applied. Brake pads consist of a friction
material bonded or riveted to a rigid backing
plate.
Brake shoe The crescent-shaped carrier to
which the brake linings are mounted and
which forces the lining against the rotating
drum during braking.
Braking systems

For more information on

braking systems, consult the Haynes
Automotive Brake Manual.
Breaker bar

A long socket wrench handle

providing greater leverage.
Bulkhead

The insulated partition between

the engine and the passenger compartment.

C

Caliper The non-rotating part of a disc-brake
assembly that straddles the disc and carries
the brake pads. The caliper also contains the
hydraulic components that cause the pads to
pinch the disc when the brakes are applied. A
caliper is also a measuring tool that can be set
to measure inside or outside dimensions of an
object.

Brake bleeding

Bearing

Axle assembly

Anti-seize compound

Alternator (exploded view)

Air filter

Glossary of Technical Terms

REF•21

REF

Camshaft A rotating shaft on which a series
of cam lobes operate the valve mechanisms.
The camshaft may be driven by gears, by
sprockets and chain or by sprockets and a
belt.
Canister

A container in an evaporative

emission control system; contains activated
charcoal granules to trap vapours from the
fuel system.

Carburettor A device which mixes fuel with
air in the proper proportions to provide a
desired power output from a spark ignition
internal combustion engine.

Castellated Resembling the parapets along
the top of a castle wall. For example, a
castellated balljoint stud nut.

Castor In wheel alignment, the backward or
forward tilt of the steering axis. Castor is
positive when the steering axis is inclined
rearward at the top.

Catalytic converter A silencer-like device in
the exhaust system which converts certain
pollutants in the exhaust gases into less
harmful substances.

Circlip

A 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.
Clearance

The amount of space between

two parts. For example, between a piston and
a cylinder, between a bearing and a journal,
etc.
Coil spring A 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.
Compression

Reduction in volume, and

increase in pressure and temperature, of a
gas, caused by squeezing it into a smaller
space.
Compression ratio The 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) joint

A type of

universal joint that cancels out vibrations
caused by driving power being transmitted
through an angle.
Core plug A 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. 
Crankcase

The lower part of the engine

block in which the crankshaft rotates.
Crankshaft

The main rotating member, or

shaft, running the length of the crankcase,
with offset “throws” to which the connecting
rods are attached.

Crocodile clip See Alligator clip

D

Diagnostic code Code 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 brake A 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.

Driveshaft

Any shaft used to transmit

motion. Commonly used when referring to the
axleshafts on a front wheel drive vehicle.

Drum brake A 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.

Castellated nut

Catalytic converter

Crankshaft assembly

Carburettor

Canister

Drum brake assembly

Accessory drivebelts

Driveshaft

REF•22

Glossary of Technical Terms

E

EGR valve A 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 brake

A 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.
Endfloat

The 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 manifold

A part with several

passages through which exhaust gases leave
the engine combustion chambers and enter
the exhaust pipe.

F

Fan clutch

A viscous (fluid) drive coupling

device which permits variable engine fan
speeds in relation to engine speeds.

Feeler blade A thin strip or blade of hardened
steel, ground to an exact thickness, used to
check or measure clearances between parts.

Firing order The 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 play The 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.
Fuse

An 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 link

A 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.

G

Gap

The distance the spark must travel in

jumping from the centre electrode to the side

electrode in a spark plug. Also refers to the
spacing between the points in a contact
breaker assembly in a conventional points-
type ignition, or to the distance between the
reluctor or rotor and the pickup coil in an
electronic ignition.
Gasket Any thin, soft material - usually cork,
cardboard, asbestos or soft metal - installed
between two metal surfaces to ensure a good
seal. For instance, the cylinder head gasket
seals the joint between the block and the
cylinder head.

Gauge An instrument panel display used to
monitor engine conditions. A gauge with a
movable pointer on a dial or a fixed scale is an
analogue gauge. A gauge with a numerical
readout is called a digital gauge. 

H

Halfshaft

A rotating shaft that transmits

power from the final drive unit to a drive
wheel, usually when referring to a live rear
axle.
Harmonic balancer

A device designed to

reduce torsion or twisting vibration in the
crankshaft. May be incorporated in the
crankshaft pulley. Also known as a vibration
damper.
Hone

An abrasive tool for correcting small

irregularities or differences in diameter in an
engine cylinder, brake cylinder, etc.
Hydraulic tappet

A tappet that utilises

hydraulic pressure from the engine’s
lubrication system to maintain zero clearance
(constant contact with both camshaft and
valve stem). Automatically adjusts to variation
in valve stem length. Hydraulic tappets also
reduce valve noise.

I

Ignition timing

The moment at which the

spark plug fires, usually expressed in the
number of crankshaft degrees before the
piston reaches the top of its stroke.
Inlet manifold

A tube or housing with

passages through which flows the air-fuel
mixture (carburettor vehicles and vehicles with
throttle body injection) or air only (port fuel-
injected vehicles) to the port openings in the
cylinder head.

Exhaust manifold

Feeler blade

Adjusting spark plug gap

Gasket

EGR valve

Glossary of Technical Terms

REF•23

REF

J

Jump start Starting the engine of a vehicle
with a discharged or weak battery by
attaching jump leads from the weak battery to
a charged or helper battery.

L

Load Sensing Proportioning Valve (LSPV) A
brake hydraulic system control valve that
works like a proportioning valve, but also
takes into consideration the amount of weight
carried by the rear axle.
Locknut A nut used to lock an adjustment
nut, or other threaded component, in place.
For example, a locknut is employed to keep
the adjusting nut on the rocker arm in
position.
Lockwasher A form of washer designed to
prevent an attaching nut from working loose.

M

MacPherson strut

A type of front

suspension system devised by Earle
MacPherson at Ford of England. In its original
form, a simple lateral link with the anti-roll bar
creates the lower control arm. A long strut - an
integral coil spring and shock absorber - is
mounted between the body and the steering
knuckle. Many modern so-called MacPherson
strut systems use a conventional lower A-arm
and don’t rely on the anti-roll bar for location.
Multimeter An electrical test instrument with
the capability to measure voltage, current and
resistance.

N

NOx

Oxides of Nitrogen. A common toxic

pollutant emitted by petrol and diesel engines
at higher temperatures. 

O

Ohm

The unit of electrical resistance. One

volt applied to a resistance of one ohm will
produce a current of one amp.
Ohmmeter

An instrument for measuring

electrical resistance.
O-ring

A type of sealing ring made of a

special rubber-like material; in use, the O-ring
is compressed into a groove to provide the
sealing action.

Overhead cam (ohc) engine An engine with
the camshaft(s) located on top of the cylinder
head(s).
Overhead valve (ohv) engine An engine with
the valves located in the cylinder head, but
with the camshaft located in the engine block.
Oxygen sensor

A device installed in the

engine exhaust manifold, which senses the
oxygen content in the exhaust and converts
this information into an electric current. Also
called a Lambda sensor.

P

Phillips screw A type of screw head having a
cross instead of a slot for a corresponding
type of screwdriver.
Plastigage

A thin strip of plastic thread,

available in different sizes, used for measuring
clearances. For example, a strip of Plastigage
is laid across a bearing journal. The parts are
assembled and dismantled; the width of the
crushed strip indicates the clearance between
journal and bearing.

Propeller shaft

The long hollow tube with

universal joints at both ends that carries
power from the transmission to the differential
on front-engined rear wheel drive vehicles.
Proportioning valve

A hydraulic control

valve which limits the amount of pressure to
the rear brakes during panic stops to prevent
wheel lock-up.

R

Rack-and-pinion steering A steering system
with a pinion gear on the end of the steering
shaft that mates with a rack (think of a geared
wheel opened up and laid flat). When the
steering wheel is turned, the pinion turns,
moving the rack to the left or right. This
movement is transmitted through the track
rods to the steering arms at the wheels.
Radiator A liquid-to-air heat transfer device
designed to reduce the temperature of the
coolant in an internal combustion engine
cooling system. 
Refrigerant Any substance used as a heat
transfer agent in an air-conditioning system.
R-12 has been the principle refrigerant for
many years; recently, however, manufacturers
have begun using R-134a, a non-CFC
substance that is considered less harmful to

the ozone in the upper atmosphere.
Rocker arm A lever arm that rocks on a shaft
or pivots on a stud. In an overhead valve
engine, the rocker arm converts the upward
movement of the pushrod into a downward
movement to open a valve.
Rotor

In a distributor, the rotating device

inside the cap that connects the centre
electrode and the outer terminals as it turns,
distributing the high voltage from the coil
secondary winding to the proper spark plug.
Also, that part of an alternator which rotates
inside the stator. Also, the rotating assembly
of a turbocharger, including the compressor
wheel, shaft and turbine wheel.
Runout

The amount of wobble (in-and-out

movement) of a gear or wheel as it’s rotated.
The amount a shaft rotates “out-of-true.” The
out-of-round condition of a rotating part.

S

Sealant

A liquid or paste used to prevent

leakage at a joint. Sometimes used in
conjunction with a gasket.
Sealed beam lamp An older headlight design
which integrates the reflector, lens and
filaments into a hermetically-sealed one-piece
unit. When a filament burns out or the lens
cracks, the entire unit is simply replaced.
Serpentine drivebelt

A single, long, wide

accessory drivebelt that’s used on some
newer vehicles to drive all the accessories,
instead of a series of smaller, shorter belts.
Serpentine drivebelts are usually tensioned by
an automatic tensioner.

Shim Thin spacer, commonly used to adjust
the clearance or relative positions between
two parts. For example, shims inserted into or
under bucket tappets control valve
clearances. Clearance is adjusted by
changing the thickness of the shim.
Slide hammer A special puller that screws
into or hooks onto a component such as a
shaft or bearing; a heavy sliding handle on the
shaft bottoms against the end of the shaft to
knock the component free.
Sprocket

A tooth or projection on the

periphery of a wheel, shaped to engage with a
chain or drivebelt. Commonly used to refer to
the sprocket wheel itself.
Starter inhibitor switch On vehicles with an

O-ring

Serpentine drivebelt

Plastigage