1.1.10 Brake servo units and master cylinder (hydraulic systems)

Official wording

The defect clauses

1. 1.1.10 (a)(i)Major

   Brake servo defective or ineffective

   Brake servo or vacuum system defective explained: what it means and what puts it right

2. 1.1.10 (a)(ii)Dangerousunder 0.1 per 100 fails

   Brake servo inoperative

   Brake servo or vacuum system defective explained: what it means and what puts it right

3. 1.1.10 (b)(i)Major

   Master cylinder defective but brake still operating

4. 1.1.10 (b)(ii)Dangerousunder 0.1 per 100 fails

   Master cylinder leaking

5. 1.1.10 (c)Major

   Master cylinder insecure

6. 1.1.10 (d)(i)Minor

   Brake fluid below minimum mark

   Brake fluid level below minimum explained: what it means and what puts it right

7. 1.1.10 (d)(ii)Majorunder 0.1 per 100 fails

   Brake fluid significantly below minimum mark

   Brake fluid level below minimum explained: what it means and what puts it right

8. 1.1.10 (d)(iii)Dangerousunder 0.1 per 100 fails

   Brake fluid not visible

9. 1.1.10 (e)Majorunder 0.1 per 100 fails

   Master cylinder reservoir cap missing

10. 1.1.10 (f)Minor

    Brake fluid warning light illuminated or defective

11. 1.1.10 (g)Minor

    Incorrect functioning of brake fluid level warning device

    Brake fluid level below minimum explained: what it means and what puts it right

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. 5 of 11 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
• 1.1.3Air and vacuum systems
• 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
• 1.1.11Rigid 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 1.1.10 mean on an MOT certificate?

It refers to sub-section 1.1.10 of the MOT inspection manual, "Brake servo units and master cylinder (hydraulic systems)", within section 1, brakes. The letter or letters after it — (a), (b)(i) and so on — identify the specific defect from the 11 listed here. 3 of them are graded Dangerous, 5 Major and 3 Minor.

Which brake servo units and master cylinder (hydraulic systems) defect is recorded most often?

"Brake fluid significantly below minimum mark" (1.1.10 (d)(ii)), recorded about 0.0 times per 100 failed MOT tests nationally. We explain what it means and what puts it right.

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.