Although many car owners believe that modern cars are too complicated for
them to work on, this is not so. Routine tasks can be done by anybody - if
they know what they are doing.
With the Seriously Useful Info series,
our mission is to give you a greater understanding of your car and provide
you with essential tips, advice and tasks that will aid trouble-free motoring.
For example: how to check tyres and engine fluids, replace wiper blades,
light bulbs and spark plugs, how to conduct a pre-MOT test check and what
to do before taking your car on holiday or abroad.
Links to the other Seriously Useful Info features
appear at the bottom of this page.
Most MoT failures are due to something quite simple, such as a blown light bulb or a worn out windscreen wiper blade. Putting everything right before the test will save the inconvenience and expense of a re-test. It will also be a lot cheaper than paying garage labour rates for things you can do yourself.
We show you how to check your car before you put it in for the test. If there is anything wrong, you'll find help on how to fix basic problems in our comprehensive manual on car and motoring care, The Haynes Glovebox Car Book. For more involved issues look in the appropriate Haynes Service and Repair Manual for your car.
It has only been possible to summarise the test requirements here, based on the regulations in force at the time of publication. Test standards are becoming increasingly stringent, although in some cases there are exemptions for older vehicles.
The help of an assistant will be necessary to carry out these checks thoroughly. The checks have been sub-divided into four categories. Please click on a category heading for details on the checks.
Test the
operation of the handbrake. Excessive travel (too many clicks)
indicates incorrect brake or cable adjustment.
Check that
the handbrake cannot be released by tapping the lever sideways.
Check the
security of the lever mountings.
2 Footbrake
Depress the
brake pedal and check that it does not creep down to the floor,
indicating a master cylinder fault. Release the pedal, wait a
few seconds, then depress it again. If the pedal travels nearly
to the floor before firm resistance is felt, brake adjustment
or repair is necessary. If the pedal feels spongy, there is air
in the hydraulic system which must be removed by bleeding.
Check that
the brake pedal is secure and in good condition. Check also for
signs of fluid leaks on the pedal, floor or carpets, which would
indicate failed seals in the brake master cylinder.
Check the
servo unit (when applicable) by operating the brake pedal several
times, then keeping the pedal depressed and starting the engine.
As the engine starts, the pedal will move down slightly. If not,
the vacuum hose or the servo itself may be faulty.
3 Steering wheel and column
Examine the
steering wheel for fractures or looseness of the hub, spokes or
rim.
Move the
steering wheel from side to side and then up and down.
Check that
the steering wheel is not loose on the column, indicating wear
or a loose retaining nut. Continue moving the steering wheel as
before, but also turn it slightly from left to right.
Check that
the steering wheel is not loose on the column, and that there
is no abnormal movement of the steering wheel, indicating wear
in the column support bearings or couplings.
4 Windscreen and mirrors
The windscreen
must be free of cracks or other significant damage within the
driver's field of view (small stone chips are acceptable).
Rear view
mirrors must be secure, intact, and capable of being adjusted.
5 Seat belts and seats
The following
checks are applicable to all seat belts, front and rear:
Examine the webbing of all the belts (including rear belts if fitted)
for cuts, serious fraying or deterioration. Fasten and unfasten
each belt to check the buckles. If applicable, check the retracting
mechanism. Check the security of all seat belt mountings accessible
from inside the vehicle.
The front
seats themselves must be securely attached and the backrests must
lock in the upright position.
6 Doors
Both front
doors must be able to be opened and closed from outside and inside,
and must latch securely when closed.
Number plates
must be in good condition, secure and legible, with letters and
numbers correctly spaced - spacing at (B) should be twice that
at (A).
The VIN plate
and/or homologation plate must be legible.
8 Electrical equipment
Switch on
the ignition and check the operation of the horn.
Check the
windscreen washers and wipers, examining the wiper blades; renew
damaged or perished blades. Also check the operation of the stoplights.
Check the
operation of the sidelights and number plate lights. The lenses
and reflectors must be secure, clean and undamaged.
Check the
operation and alignment of the headlights. The headlight reflectors
must not be tarnished and the lenses must be undamaged.
Switch on
the ignition and check the operation of the direction indicators
(including the instrument panel tell-tale) and the hazard warning
lights. Operation of the sidelights and stop-lights must not affect
the indicators - if it does, the cause is usually a bad earth
at the rear light cluster.
Check the
operation of the rear foglight(s), including the warning light
on the instrument panel or in the switch.
The ABS and airbag
warning lights (as applicable) must operate as specified by the car maker.
This usually means lighting up when the ignition is switched on,
then going out and staying out.
9 Footbrake
Examine the
master cylinder, brake pipes and servo unit for leaks, loose mountings,
corrosion or other damage.
The fluid
reservoir must be secure and the fluid level must be between the
upper (MAX) and lower (MIN) markings.
Inspect both
front brake flexible hoses for cracks or deterioration of the
rubber. Turn the steering from lock to lock, and ensure that the
hoses do not contact the wheel, tyre, or any part of the steering
or suspension mechanism. With the brake pedal firmly depressed,
check the hoses for bulges or leaks under pressure.
10 Steering and suspension
Have your
assistant turn the steering wheel from side to side slightly,
up to the point where the steering gear just begins to transmit
this movement to the roadwheels. Check for excessive free play
between the steering wheel and the steering gear, indicating wear
or insecurity of the steering column joints, the column-to-steering
gear coupling, or the steering gear itself.
Have your
assistant turn the steering wheel more vigorously in each direction,
so that the roadwheels just begin to turn. As this is done, examine
all the steering joints, linkages, fittings and attachments. Renew
any component that shows signs of wear or damage. On vehicles
with power steering, check the security and condition of the steering
pump, drivebelt and hoses.
Check that
the vehicle is standing level, and at approximately the correct
ride height.
11 Shock absorbers
Depress each
corner of the vehicle in turn, then release it. The vehicle should
rise and then settle in its normal position. If the vehicle continues
to rise and fall, the shock absorber is defective.
A shock absorber
which has seized will also cause the vehicle to fail.
12 Exhaust system
Start the
engine. With your assistant holding a rag over the tailpipe, check
the entire system for leaks. Repair or renew leaking sections.
Jack up the
front and rear of the vehicle, and securely support it on axle
stands. Position the stands clear of suspension assemblies. Ensure
that the wheels are clear of the ground and that the steering
can be turned from lock to lock.
Starting
at the front right-hand side, grasp the road-wheel at the 3 o'clock
and 9 o'clock positions and shake it vigorously.
Check for
free play or insecurity at the wheel bearings, suspension balljoints,
or suspension mountings, pivots and attachments.
Now grasp
the wheel at the 12 o'clock and 6 o'clock positions and repeat
the previous inspection. Spin the wheel, and check for roughness
or tightness of the front wheel bearing.
If excess
free play is suspected at a component pivot point, this can be
confirmed by using a large screwdriver or similar tool and levering
between the mounting and the component attachment. This will confirm
whether the wear is in the pivot bush, its retaining bolt, or
in the mounting itself (the bolt holes can often become elongated).
Carry out
all the above checks at the other front wheel, and then at both
rear wheels.
15
Springs and shock absorbers
Examine the
suspension struts (when applicable) for serious fluid leakage,
corrosion, or damage to the casing. Also check the security of
the mounting points.
If coil springs
are fitted, check that the spring ends locate correctly in their
seats, and that the spring is not badly corroded, cracked or broken.
If leaf springs
are fitted, check that all leaves are intact, that the axle is
securely attached to each spring, and that there is no deterioration
of the spring eye mountings, bushes, and shackles.
The same
general checks apply to vehicles fitted with other suspension
types, such as torsion bars, hydraulic displacer units, etc. Ensure
that all mountings and attachments are secure, that there are
no signs of excessive wear, corrosion or damage, and (on hydraulic
types) that there are no fluid leaks or damaged pipes.
Inspect the
shock absorbers for signs of serious fluid leakage. Check for
wear of the mounting bushes or attachments, or damage to the body
of the unit.
16
Driveshafts (fwd vehicles only)
Rotate each
front wheel in turn and inspect the constant velocity joint gaiters
for splits or damage.
Also check
that each driveshaft is straight and undamaged.
17
Braking system
If possible
without dismantling, check brake pad wear and disc condition.
Ensure that the friction lining material has not worn excessively,
and that the discs are not fractured, pitted, scored or badly
worn.
Examine all
the rigid brake pipes underneath the vehicle, and the flexible
hose(s) at the rear. Look for corrosion, chafing or insecurity
of the pipes, and for signs of bulging under pressure, chafing,
splits or deterioration of the flexible hoses.
Look for
signs of fluid leaks at the brake calipers or on the brake backplates.
Repair or renew leaking components.
Slowly spin
each wheel, while your assistant depresses and releases the footbrake.
Ensure that each brake is operating and does not bind when the
pedal is released.
Examine the
handbrake mechanism, checking for frayed or broken cables, excessive
corrosion, or wear or insecurity of the linkage. Check that the
mechanism works on each relevant wheel, and releases fully, without
binding.
It is not
possible to test brake efficiency without special equipment, but
a road test can be carried out later to check that the vehicle
pulls up in a straight line.
18
Fuel and exhaust systems
Inspect the
fuel tank (including filler cap), fuel pipes, hoses and unions.
All components must be secure and free from leaks.
Examine the
exhaust system over its entire length, checking for any damaged,
broken or missing mountings, security of the retaining clamps
and rust or corrosion.
19
Wheels and tyres
Examine
the sidewalls and tread area of each tyre in turn. Check for cuts,
tears, lumps, bulges, separation of the tread, and exposure of
the ply or cord. Check that the tyre bead is correctly seated
on the wheel rim, that the valve is sound and properly seated,
and that the wheel is not distorted or damaged.
Check that
the tyres are of the correct size for the vehicle, that they are
of the same size and type on each axle, and that the pressures
are correct.
Check the
tyre tread depth. The legal minimum at the time of writing is
1.6 mm over at least three-quarters of the tread width. Abnormal
wear may indicate incorrect front wheel alignment.
20
Body corrosion
Check the
condition of the entire vehicle structure for signs of corrosion
in load-bearing areas. (these include chassis box sections, side
sills, cross-members, pillars, and all suspension, steering, braking
system and seat belt mountings and anchorage) Any corrosion which
has seriously reduced the thickness of a load-bearing area is
likely to cause the vehicle to fail. In this case professional
repairs are likely to be needed.
Damage or
corrosion which causes sharp or otherwise dangerous edges to be
exposed will also cause the vehicle to fail.
Have the
engine at normal operating temperature, and make sure that it
is in good tune (ignition system in good order, air filter element
clean, etc).
Before any
measurements are carried out, raise the engine speed to around
2500 rpm, and hold it at this speed for 20 seconds. Allow the
engine speed to return to idle, and watch for smoke emissions
from the exhaust tailpipe. If the idle speed is obviously much
too high, or if dense blue or clearly-visible black smoke comes
from the tailpipe for more than 5 seconds, the vehicle will fail.
As a rule of thumb, blue smoke signifies oil being burnt (engine
wear) while black smoke signifies unburnt fuel (dirty air cleaner
element, or other carburettor or fuel system fault).
An exhaust
gas analyser capable of measuring carbon monoxide (CO) and hydrocarbons
(HC) is now needed. If such an instrument cannot be hired or borrowed,
a local garage may agree to perform the check for a small fee.
The permitted emission levels in the following paragraphs vary according to the age of the vehicle. If a vehicle has been fitted with an engine taken from an older vehicle, it only has to meet the emission levels applicable to the older vehicle. It will be necessary to provide the MoT tester with satisfactory proof of the age of the donor vehicle (for instance, a registration document showing the engine number).
22
CO emissions (mixture)
At the time
of writing, for vehicles first used between 1st August 1975 and
31st July 1986 (P to C registration), the CO level must not
exceed
4.5% by volume. For vehicles first used between 1st August 1986
and 31st July 1992 (D to J registration), the CO level must
not
exceed 3.5% by volume. Vehicles first used after 1st August 1992
(K registration) must conform to the manufacturer's specification.
The MOT tester has access to a DOT database or emissions handbook,
which lists the CO and HC limits for each make and model of
vehicle.
The CO level is measured with the engine at idle speed, and at "fast idle". The following limits are given as a general guide:
At idle speed - CO level no more than 0.5% At "fast idle" (2500
to 3000 rpm) - CO level no more than 0.3% (minimum oil temperature
60ºC) If the CO level cannot be reduced far enough to pass the
test (and the fuel and ignition systems are otherwise in good
condition) then the carburettor is badly worn, or there is some
problem in the fuel injection system or catalytic converter (as
applicable).
23
HC emissions
With the
CO within limits, HC emissions for vehicles first used between
1st August 1975 and 31st July 1992 (P to J registration) must
not exceed 1200 ppm. Vehicles first used after 1st August 1992
(K registration) must conform to the manufacturer's specification.
The MOT tester has access to a DOT database or emissions handbook,
which lists the CO and HC limits for each make and model of
vehicle.
The HC level is measured with the engine at "fast idle". The following
is given as a general guide: At "fast idle" (2500 to 3000 rpm)
- HC level no more than 200 ppm (minimum oil temperature 60ºC)
Excessive
HC emissions are caused by incomplete combustion, the causes of
which can include oil being burnt, mechanical wear and ignition/fuel
system malfunction.
24
Diesel models
The only
emission test applicable to Diesel engines is the measuring of
exhaust smoke density. The test involves accelerating the engine
several times to its maximum unloaded speed. Note: it is of the utmost importance
that the engine timing belt is in good condition before the test
is carried out.
The limits
for Diesel engine exhaust smoke, introduced in September 1995
are:
Vehicles first used before 1st August 1979: Exempt from metered
smoke testing, but must not emit "dense
blue or clearly visible black smoke for a period of more than
5 seconds at idle"
or "dense blue or clearly
visible black smoke during acceleration which would obscure the
view of other road users".
Non-turbocharged vehicles first used after 1st August 1979: 2.5m-1
Turbocharged vehicles first used after 1st August 1979: 3.0m-1
Excessive
smoke can be caused by a dirty air cleaner element. Otherwise,
professional advice may be needed to find the cause.
Note
for visitors from outside the UK: the MoT test is performed
annually on all vehicles 3 years old or more. Most countries have
something similar, but the details will vary.
'Haynes Publishing' is the trade name of JH Haynes & Co Ltd ( Company Number 1449587 ). Both this company & its parent company, Haynes Publishing Group P.L.C. ( Company Number 659701 ), are registered in England & Wales and their Registered Office is at Sparkford, Yeovil, Somerset, BA22 7JJ, England.
Examine
the sidewalls and tread area of each tyre in turn. Check for cuts,
tears, lumps, bulges, separation of the tread, and exposure of
the ply or cord. Check that the tyre bead is correctly seated
on the wheel rim, that the valve is sound and properly seated,
and that the wheel is not distorted or damaged.