Posts Categorized ‘The MOT Test’

June 21, 2007 at 3:41 pm

THE MoT TEST Fuel and Emissions

The Mot test Inspection Manual now moves onto Fuel and Emissions and is divided into four sub-sections: exhaust system, fuel system, exhaust emissions-spark ignition and exhaust emissions-compression ignition.

As with almost all of the Inspection Manual, the tester is not obliged to follow any set examination order as long as the test is carried out to the correct standards with no omissions. In this section I will deal with each subject in the order it appears in the manual. Read the rest of this entry »

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June 7, 2007 at 11:30 am

THE MoT TEST Body and Structure

The Inspection Manual section next under our gaze is that entitled Body and Structure which is self explanatory, but also includes sub sections on doors, seats, registration plates, vehicle Identification Numbers, load security, spare wheel and carrier.

Body & Structure

For the tester the main criteria during inspection is that of damage, fracture or corrosion which may affect the correct functioning of the steering and/or braking system but not within a prescribed area, these prescribed areas those that are specifically dealt with in the sections of the Inspection Manual covering steering/suspension, brakes and seat belts. In the case of any of the above faults, damage, corrosion etc, it is the responsibility of the tester to employ qualification and experience in deciding whether the area of bodywork or structure is adversely affected, if this is not the case then the tester would normally issue an advisory notice. Another area which must be examined concerns vehicles which have a separate chassis to which the bodywork is mounted, here the nominated tester must check for corrosion, damage etc which seriously affects any chassis/body mounting plus any insecurity allowing excessive body movement relative to the chassis which may cause loss of vehicle control.

Whilst dealing with vehicle Body and structure an examination must be made for any sharp edge or projection caused by damage or corrosion which may make the vehicle dangerous to other road users, the term road user also includes pedestrians and any such damage will fail.

Moving on now to the vehicle doors which must latch securely in the closed position. The tester must check the drivers door and the front passenger door to ensure that they can be opened from both inside and outside. This particular stipulation does not apply to two vehicle types 1) vehicles which have been customised to the extent that no door exists and 2) vehicles specially modified for the carriage of high value cargo.

Another very short sub-section concerns the vehicle seating, basically the regulations insist on security of the driver and front passenger seat plus checks to ensure that all seat backrests can be secured in the upright position. The main reason for the above requirements is to ensure that the seat belts can do their job effectively.

We move now into the realms of registration plates and Vehicle Identification Numbers (VIN). The regulations stipulate that a registration plate will fail the test if it is: missing or incorrect, so insecure that it may fall off, letters of figures missing or incomplete, faded, dirty, obscured or deteriorated. To underline the required standards the inspection manual states likely to be mis-read or is not easily legible by a person standing approximately 20 metres to the front/rear of the vehicle. We have all seen or may even use registration plates which fall into the following areas for MoT test fail: letters and/or figures obviously incorrectly spaced, a figure or letter not correctly formed or likely to be mis-read, a letter or figure which is obviously not of equal width along its entire length, any feature on a number plate that has the effect of changing the appearance or legibility of any of the characters so that the true identity of the vehicle is less easily identified. The inspection manual also makes special mention of badly positioned or uncovered retaining bolts etc which have been placed to change the appearance of a letter or figure, another guaranteed MoT fail.

Vehicle Identification Numbers have been a test requirement since August 1980 although of course their use goes back to the start of motor vehicle production. The VIN requirements are that it must be present and either displayed on a VIN plate secured to the vehicle or stamped/etched into the vehicle chassis or bodywork, most manufacturers of course employ both. Fail criteria for VIN are: not permanently displayed or not legible and more than one different VIN displayed.

The last sub-section of the Body and Structure part of the MoT Inspection Manual deals with load security and spare wheel and carrier. Load security does not mean how effectively a load is tied to the vehicle at the time of the test, it means the effectiveness of securing a load within the confines of the vehicle body., to make clearer still, the MoT inspection procedure must include checks on any bootlid, tailgate, loading door, HINGED tailboard or dropside ensuring that it is or can be secured in the closed position. Obviously the safety of other road users is paramount so any locks, catches etc cannot be substituted by lengths of rope, wire and the like.

Spare wheel and carrier relates to the security of external spare wheels and their associated fixings.  The tester must inspect such items ensuring that they are not in such a condition as they may fall off.

Remember if you need repairs to your vehicle you can get parts for any vehicle including Vauxhall Vectra parts from Carsparefinder and have a garage fit them for you, by supplying the Vauxhall parts yourself the garage will cut the bill as they will not have to pay for those expensive new parts.

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May 31, 2007 at 11:17 am

THE MOT TEST – Seat Belts

Without any doubt the introduction of vehicle seat belts has saved many from serious injury or even death, so their inclusion into the MOT test in 1969 for front seat belts and extended to cover rear belts in 1991 was to many a foregone conclusion. Read the rest of this entry »

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May 24, 2007 at 2:13 pm

THE MoT TEST – Tyres

The inspection of the tyres is restricted to those fitted to the vehicle at the time of the test; this does not include any spare tyre/wheel.

The most obvious test requirement for tyres is of course that of wear, the tyre must have at least 1.6mm of tread depth across the central three quarters and around the entire circumference. The other basic stipulation is that the tyres fitted across the same axle must be of the same size. This size ruling also extends to the aspect ratio of the tyre, for example, a tyre 175/70×14 must not be fitted on the same axle as a 175/65×14. One slight contradiction in this area is the use of the so called “standardâ€? profile, these tyres may be marked, for example , 155×13 and have an aspect ratio of 82%, they can be fitted on the same axle as a tyre 155/80×13. This 2% difference is specifically allowed by the MoT test regulations.

When inspecting the tyres from underneath the tester will also examine each tyre for any lump or bulge which may indicate structural damage and also check that the tyres do not foul any part of the vehicle i.e. rubbing on bodywork or steering/suspension component. In the area of cuts the regulations state that any cut at least 25mm long or at least 10% of the tread width deep enough to reach the structure must fail. On the subject of structure, the tyre must not have any area of ply or cord exposed.

Another tyre feature which comes under the testers eye is that of rotation specific construction, these are easily spotted and will have a clear sidewall marking with either an arrow indicating forward direction of rotation or the word “outside� denoting outward facing fitment.

With tyre fitting in mind attention will be paid to the tyre valve ensuring that it is not damaged or seriously mis-aligned (often caused by poorly fitted wheel trims) and whether it is correctly seated on the wheel.

Moving onto the wheels, checks must be made by the tester to ensure that they are not badly damaged, distorted or cracked and in some cases where spoked wheels are fitted the spokes are not loose, bent or corroded. This reference to spokes applies equally to wire, steel and alloy construction.

Lastly, the tester will examine each road wheel for security, checking where possible for the correct number of nuts/studs/bolts. These checks must be done without disturbing any wheel trim/cap etc.

Remember if you need tyres for your vehicle weather your test is coming up or just gone Carsparefinder can locate legal Vauxhall parts or used car parts for any vehicle new or old.

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May 11, 2007 at 2:13 pm

The MoT Test – Braking Systems

The next section in the MoT Inspection Manual is that covering braking systems. By and large the basics of vehicle braking has not changed a great deal in the past fifty plus years, it is only the ancillary items such as dual circuit and anti lock systems which have had any great effect. Obviously as braking systems have evolved so have the inspection procedures within the MoT test.

As we all know the average motor vehicle has two braking systems, a mechanical park or hand brake and a hydraulic service or foot brake. Starting with the parking brake the nominated tester will usually start the inspection procedure sat in the driver’s seat and will operate the park brake lever checking for presence, security, travel and the effectiveness of the ratchet mechanism. Presence and security require little explanation other than to say that the lever must not have excessive movement on its mountings indicating loose fixing bolts and/or damage/corrosion to the mounting area. With the lever in the on position the tester must check to ensure that it cannot be knocked off thus indicating a worn or defective ratchet mechanism.  Park brake lever travel must not reach the end of the ratchet which would indicate a requirement for adjustment and/or replacement of brake components. Staying with the park brake and moving to the vehicle underside the tester will examine as much of the park mechanism as possible without dismantling or removing any covers etc, at this point the tester may request an assistant sitting in the driver’s seat to operate the park brake on and off whilst observing the movement of cables etc and checking for unusual movement around any panelwork supporting any part of the system. Any such movement should be investigated as far as possible bearing in mind the “no dismantling� rule and it is here that the testers previous experience may well come into play identifying whether the abnormality is due to a weakness affecting a particular make/model.

Moving on now to the service brakes and again starting in the driver’s seat and checking the “feel� of the brake pedal checking for excessive travel before brake pressure is felt, presence of the pedal rubber pad/anti slip device plus any abnormal play i.e., side to side, indicating excessive play in the pedal pivots. One other check whilst in the driving position is for brake servo operation, with the engine off the brake is pressed repeatedly until the pedal goes hard, now with foot pressure applied to the pedal the engine is started and if the servo is functioning the pedal will drop slightly.  The lack of pedal drop at this point would cause an MoT fail providing of course a brake servo is fitted by the vehicle manufacturer and has not been removed for some reason. Another required check whilst in the drivers seat is that for the correct functioning of the ABS warning light (where ABS is fitted by the vehicle manufacturer) this light must follow the correct sequence as stipulated by the manufacturer and normally this comprises; ABS light on with the ignition on, ABS light goes off within 5 to 20 seconds, any deviation from the specifications warrants an MoT fail.

Before the vehicle is raised the tester will move into the engine bay area and examine as far as possible all brake components looking for insecurity, excessive corrosion and leaks. With an assistant pressing the brake pedal an inspection will also be carried out on the master cylinder/servo assembly including all surrounding support panelling within 300mm again looking for any excessive damage or corrosion. Brake fluid level is also checked where possible and this must be no lower than the “minimum� level marking.

Working now under the vehicle the tester must examine all visible brake pipes and hoses, check for damage, insecurity, leakage and/or excessive corrosion/deterioration, this examination must also include time when the system is fully pressurized meaning that the engine must be running to provide power assistance and the service brake pedal applied. Any leakage will cause a fail so will any brake hose bulging under pressure. Further examination of the brake hoses will be carried out to ensure that they are not twisted, fouling any steering or suspension component especially when the steered wheels are moved from left to right. One part of the brake hose that can escape assessment is the ferrule, this is the metal union which is crimped on to the end of the hose and provides the connection for the brake caliper or cylinder. Excessive corrosion here is not acceptable and will be a fail item. Whilst on the subject of corrosion many people ask “what is excessive corrosion on a brake pipe?� According to the chapter dealing with brakes in the MoT Inspection Manual “a rigid brake pipe excessively chafed, corroded or damaged so that its wall thickness is reduced by 1/3 (approximately 0.25mm for a typical 4.75mm brake pipe) is a reason for rejection�. Obviously the only way to accurately assess this is to remove the section of pipe, clean it and measure the wall thickness with a pin anvil micrometer! Just as obvious is the impracticality, so trust is placed on the MoT tester to employ knowledge and experience in assessing a brake pipe and deciding whether pass or fail.

Having covered all the main brake components the tester must also inspect and assess other parts which have a direct effect on the brake system effectiveness. Many vehicles have a load sensing valve fitted into the brake hydraulic system which regulates the pressure available to the rear brakes dependant on vehicle load; corrosion, security and the condition of any linkages must be checked together with a check to ensure that it is not seized or has an operating lever obviously incorrectly adjusted. Other ancillary components include the vacuum pump often fitted to compression ignition engines, here the pump must be secure and its drive system in good working order, some of these pumps are belt driven and in this case the condition of the belting is checked to ensure that they are not excessively loose and/or deteriorated.

The last part of this article may well be the first or last part of the MoT test procedure that the nominated tester carries out, the brake performance test. At present the most common method of evaluating brake performance is by the use of a slow speed roller brake tester set into the floor of the test bay, there are however, other systems which use special plates, again mounted into the test lane floor and deccelerometers which are used during a road test of certain vehicles which cannot be roller brake tested due to the design of their transmission system. For now we will assume that the vehicle tested is an average family car undergoing a roller brake test.
 
With the vehicle front wheels positioned in the rollers the tester sets the machine running and records the brake efforts for each wheel by pressing the brake pedal, checks are also made on whether the brakes come on and then release evenly and should there be an imbalance between the steered wheels of 25% or more a fail will result. Moving the vehicle so that the rear wheels are sat in the rollers the tester will repeat the above test with the addition of readings from the park brake. Although there is no specific maximum out of balance reading as with the front wheels, the rear service (foot) brake efforts must increase and decrease at approximately the same rate.

The results of the roller brake test are entered into the results screen of the test station MoT computer and this will then calculate the brake efforts and display them as percentages. The requirements for service and park brakes are as follows:

  • Total Service Brake Efficiency – at least 50%
  • Brake Imbalance on Steered Wheels – no more than 25%
  • Park Brake Efficiency – at least 16%

The figures quoted above apply to dual circuit brake system as fitted to today’s vehicles; the earlier single circuit systems have a park brake requirement of 25% minimum as there is a greater reliance on the hand brake for emergencies.

In over ten years of vehicle testing I have come across many instances where a car owner has argued over a failed brake component insisting that it should have passed, I usually reply that it is far better for an MoT tester to cast doubt on a part at 0 mph than the owner have doubts at 70 mph with their loved ones on board!

Remember if your car has failed its MoT you can find all your used car parts to get your car back on the road from CarSpareFinder.

 

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May 1, 2007 at 10:03 am

THE MoT TEST – Suspension & Steering

As far as the tester is concerned one of the biggest sections in the vehicle inspection manual is that dealing with suspension and steering, although this part does deal with only two closely related sections its size is mainly due to the number of variations within each subject heading. Five or six different steering mechanisms, some common some not, five or six different types of suspension again some more common than others all add up to a forest of test requirements that can apply in one instance but not in the next, it is the responsibility of the nominated tester to identify the type of steering or suspension fitted and then apply the correct test pass/fail criteria.
Due to the variations mentioned above I shall deal with both subjects in general terms.

Starting with the steering system, the vehicle presented for test would, in most cases, be driven into the MoT area by the mechanic carrying out the test so it makes sense for the steering controls to be assessed first. Pushing and pulling the steering wheel at right angles to the steering column will show any excessive play in the top column support bearings and the possibility of the wheel not being secured to the shaft. This procedure will also show up any problems with the clamp which, when slackened, permits the steering wheel to be adjusted for height and/or reach. Turning the wheel left to right allows the tester to feel for any excessive play that may be in the steering mechanism and/or joints, flexible couplings etc. Moving to the vehicle underside and with an assistant in the drivers seat turning the wheel left to right the tester again looks for excessive play in joints, couplings and mountings. If the vehicle is fitted with power steering the tester will be looking for fluid leakage plus the security and condition of all associated hoses and pipes. On the subject of power steering, should a drive belt be missing or defective the regulations stipulate a fail situation; the same applies to the power steering pump itself. As well as the normal wear and tear in the steering system the inspection procedure also looks for evidence of excessive corrosion within 300mm of a component mounting, deliberate modification which significantly reduces the original strength, fractures, inadequate repair or distortion. It must be mentioned that the above examination also applies to the rear of the vehicle if rear wheel steering is fitted.

Moving on now to suspension, and starting with the “bounce� test on each corner of the vehicle to assess damper (shock absorber) performance, the tester is looking for excess body movement after the load is removed and this must not carry on for more than one or two up/down cycles. From the vehicle underside the tester will examine all springs looking particularly for fractures, incorrect location, modification by the use of heat, weld repair and corrosion to the extent that the spring is seriously weakened. As with the steering system excessive corrosion within 300mm of any suspension mounting point will fail. Whilst underneath an examination of the dampers is made looking particularly for serious external leaks, security, presence, plus the condition of all linkages, pivots and bushes. As there are so many variations on the basic suspension theme the inspection manual is sub divided into sections dealing with the specifics of coil, leaf, torsion bar, fluid, hydro-pneumatic suspensions,  but generally speaking the system fitted must be effective, in good working condition, free from excessive corrosion, secure, free from damage such that is function or durability is impaired and mounted to the rest of the vehicle at a point which is free from excessive corrosion to a range of 300mm. The extent to which the test covers all suspension ancillary components is clear when you consider that the inspection manual specifically mentions the following:

  • Upper and lower suspension arms/wishbones
  • Trailing arms
  • Radius arms
  • Tie bars/rods
  • Panhard rods
  • Torque/ reaction arms
  • Anti-roll bars and linkages
  • Sub-frames

As well as the main and ancillary components, the tester is required to access the presence of all locking devices fitted to the various parts, these will include the fitment of locking tabs/washers, self locking nuts or split pins.

The simple reason for this is to help prevent the nut coming loose to the extent that it could become detached and cause an assembly to separate leading to the vehicle going out of control.

Towards the end of the inspection manual section on steering and suspension we come to a small chapter dealing with wheel bearings and front drive shafts. The assessment of wheel bearings are basically checks for excessive free play, this will depend on the type of bearing fitted and also excessive noise when the wheel is rotated indicating roughness. The degree at which the roughness in the bearing becomes failable is a matter for the tester’s discretion that must employ judgement based on knowledge and experience.

The assessment of the front driveshafts basically covers security, damage and the condition of any outer gaiter which must be secure onto the joint housing, not split or missing. Any flexible couplings are also included in the inspection and they must not be excessively worn or show excessive cracking or display signs of breaking up.

Remember if you need repairs to your vehicle you can get used Vauxhall parts from car dismantlers and have the garage fit them for you, by supplying the parts yourself the garage will cut the bill as they will not have to pay for those expensive new parts.

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April 25, 2007 at 4:55 pm

THE MoT TEST – Lighting

The lighting section of the MoT covers all exterior lamps required by the Road Traffic Act; this excludes front fog lamps, reversing lights and work lights as fitted to some commercial vehicles.

By and large all required lights must switch on and off when required, be correctly positioned, give out light of the correct colour and not affect or be affected by the operation of any other light.

Firstly lets take a look at the sidelights, or more correctly, the position lights, these not only indicate the vehicles presence but also its approximate width, so a couple of white LEDs mounted in the grille is easily going to get you an MoT failure. Much the same applies to the rear position lights and in common with all other required lights must not flicker or go off when tapped lightly.  Quite common within the motoring community at the younger end of the population is the fitting of blue sidelights especially at the front, again a guaranteed MoT fail as the regulations require they must show a steady white light to the front, or a yellow light, if incorporated in a headlamp which emits a yellow lightâ€?

One particular chaffing point between vehicle owners and MoT testers is the subject of damage, I personally have seen countless lamp units of all types with holes, cracks, incomplete lenses attended by an indignant owner clutching a freshly issued fail sheet insisting that I should have used some discretion when assessing that particular lamp, the regulations however, are quite clear, and state:

A front or rear position lamp incomplete, not in good working order or not clean, i.e. damaged or deteriorated, or not visible from a reasonable distance.

If damaged, the replacement of most lamp units can be fairly easy and other than the main dealers, many suppliers can offer replacement at a competitive price and should there not be a ready source the required unit from one of the second-hand parts companies will fill the void. One recommended source for used car parts are breakers yards where you can get a fully functioning Vauxhall headlamp N/S and/or O/S for almost nothing.

The next lamps that work in conjunction with the side/position lamps are the registration plate lights. The requirements for these are straight forward and must be:

  • Fitted
  • Secure
  • Working
  • Correctly positioned
  • Not flicker when tapped
  • Not show a white light to the rear

One of the biggest problems with these lights is that of bulb holder corrosion which in turn can affect the wiring. Keeping the holder free from moisture is the basis of fault prevention and there are numerous aerosol sprays which do a fine job in keeping the bulb contacts rot free.

Whilst at the rear of the vehicle the MoT tester needs to check the rear fog light, which has been a required fitment to the offside or centre of vehicles since April 1980. This lamp must not be;

  • Missing
  • Emitting any colour other than red
  • Incomplete
  • Not in good working order
  • Insecure, obscured or not facing rearward
  • Flickers when tapped by hand
  • Affected by the operation of other lamp
  • Tell-tail (warning lamp) does not work

As with all other required lights, the switch must also meet certain specifications in that it must be present, in good working order and secure.

Another rear mounted lamp which is included in the MoT is of course the brake or stop lamps and they must obviously be fitted for the inspection to proceed. Since January 1971 a vehicle must be fitted with two stop lights and they must emit a steady red light when the service brakes are operated, go off, be complete, clean, in good working order, secure and face rearward. One minor quirk of the regulations is that additional stop lamps are not a testable item IF there is doubt as to whether they are connected.

Also tested whilst at the rear of the vehicle are the indicators which of course are fitted to all four corners and since April 1986 must include side repeaters. In common with all other required lamps they must be in good working condition, present, secure, showing light of the appropriate colour (amber) or affected by the operation of another lamp. Different to any other lamp of course is that they must flash at a rate of between one and two times per second (60-120 times per minute).

Closely related to the indicators are the hazard warning lights which have been a required fitment since April 1986. By the operation of a single switch all indicators must flash in phase with both the ignition on and off. In common with the indicators is the requirement for a “tell tale� to warn the driver that the hazard lights are on.

Last but certainly not least are the headlamps which have the same basic requirements as the other lights, security, condition etc but also have a requirement regarding aim. Basically, this is checked with the headlamp aligner which when correctly positioned in front of each headlamp in turn will, with the lamp on, display the projected beam image which has the following requirements: flat horizontal illumination just below the straight ahead a kick up image rising above the horizontal and away to the left, the point at which the image kicks up must be just to the left of the vertical centre line. Any deviation from the above will result in a fail unless it can be corrected via the “height adjuster control by the driver or by simple adjustment which is now permitted to be carried out during the test. The other variation from the norm is that headlamps are permitted to show either a yellow or substantially white light, anything else will fail.

I am sure that it will come as no surprise that the most common reason for MoT failure in automotive lighting is blown bulbs, a quick replacement and that’s that. Another very common area is that of headlamp aim and in many cases a tweak with a screwdriver will suffice and if at all possible this should be done by the MoT station as they will have access to the correct alignment equipment.

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