1.1.3 Air and vacuum systems

Official wording

The defect clauses

1. 1.1.3 (a)(i)Major

   Insufficient pressure/vacuum assistance for less than four brake applications after the warning device has operated (or gauge shows an unsafe reading)

2. 1.1.3 (a)(ii)Dangerous

   Insufficient pressure/vacuum assistance for less than two brake applications after warning device has operated (or gauge shows an unsafe reading)

3. 1.1.3 (b)Major

   Time taken to build up air pressure/vacuum to safe working value not in accordance with the requirements

4. 1.1.3 (c)Major

   Repeated operation of any ancillary air or vacuum system completely depletes the stored air or vacuum for the braking system

5. 1.1.3 (d)Major

   Air leak causing a noticeable drop in pressure or audible air leak

6. 1.1.3 (e)Major

   External damage likely to affect the function of the braking system

Wording and categories reproduced from the DVSA inspection manual under the Open Government Licence. Frequencies are items per 100 failed class 4 tests across the DVSA anonymised MOT dataset; a clause with no figure was not recorded often enough to appear in any model’s top forty failure items. 0 of 6 clauses link to our own explanation.

Grading

What the categories mean

Dangerous

a direct and immediate risk to road safety or the environment. The vehicle fails and must not be driven until repaired, even to a garage.

Major

a defect that affects safety, the environment or other road users. The vehicle fails.

Minor

a defect with no significant effect on safety or the environment. Recorded on the certificate; the vehicle passes.

The full guide to defect grading

Section 1

Other sub-sections of brakes

• 1.1.1Service brake pedal or hand lever pivot
• 1.1.2Service brake pedal or hand lever condition and travel
• 1.1.4Low-pressure warning
• 1.1.5Hand operated brake control valve
• 1.1.6Parking brake lever or control
• 1.1.7Brake valves
• 1.1.9Pressure storage reservoirs
• 1.1.10Brake servo units and master cylinder (hydraulic systems)
• 1.1.11Rigid brake pipes
• 1.1.12Flexible brake hoses
• 1.1.13Brake linings and pads
• 1.1.14Brake discs and drums
• 1.1.15Brake cables, rods, levers and linkages
• 1.1.16Brake actuators - including spring brakes, hydraulic cylinders and callipers
• 1.1.17Load sensing valve
• 1.1.18Brake slack adjuster
• 1.1.19Additional braking device (retarder), if fitted
• 1.1.21Complete braking system
• 1.2.1Performance
• 1.2.2Efficiency
• 1.3.1Performance
• 1.3.2Efficiency
• 1.4.1Performance
• 1.5Additional braking device (retarder) performance
• 1.6Anti-lock braking system (ABS)
• 1.7Electronic braking system (EBS)
• 1.8Brake fluid

All sections of the manual

Common questions

What does 1.1.3 mean on an MOT certificate?

It refers to sub-section 1.1.3 of the MOT inspection manual, "Air and vacuum systems", within section 1, brakes. The letter or letters after it — (a), (b)(i) and so on — identify the specific defect from the 6 listed here. 1 of them is graded Dangerous, 5 Major and 0 Minor.

Which air and vacuum systems defect is recorded most often?

None of the clauses in this sub-section appears among the most-recorded failure items nationally; they are rare in practice.

Does a Minor defect fail the MOT?

No. a defect with no significant effect on safety or the environment. Recorded on the certificate; the vehicle passes. Major and Dangerous defects fail. A Dangerous defect also means the car must not be driven until it is repaired.