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Dangerous MOT Failures - Brakes
Part of the Dangerous MOT Failures Explained series.
Brake performance is one of the most critical aspects of vehicle safety. Any major failure in this system - like a leaking master cylinder or inoperative servo - is treated as a serious risk by MOT testers.
We’ve listed 32 brake-related dangerous MOT faults that instantly fail a test.
These problems result in severely compromised stopping power and must be fixed before driving. A new MOT Test will also be required once the fixes are made.
Full List of Dangerous MOT Faults: Brakes
| Vehicle System / Component | MOT Manual Reference | Specific Fault / Issue | Description | MOT Fault Category |
| Brakes | 1.1.3. Air and vacuum systems | (a) Insufficient pressure/vacuum assistance for less than | (ii) two brake applications after warning device has operated (or gauge shows an unsafe reading) | Dangerous |
| Brakes | 1.1.7. Brake valves | (a) Valve | (ii) leaking such that brake functionality is affected | Dangerous |
| Brakes | 1.1.7. Brake valves | (d) Hydraulic fluid | (ii) leak from a brake valve such that brake functionality is affected | Dangerous |
| Brakes | 1.1.10. Brake servo units and master cylinder (hydraulic systems) | (a) Brake servo | (ii) inoperative | Dangerous |
| Brakes | 1.1.10. Brake servo units and master cylinder (hydraulic systems) | (b) Master cylinder | (ii) leaking | Dangerous |
| Brakes | 1.1.10. Brake servo units and master cylinder (hydraulic systems) | (d) Brake fluid | (iii) not visible | Dangerous |
| Brakes | 1.1.11. Rigid brake pipes | (a) Brake pipe is at imminent risk of failure or fracture | N/A | Dangerous |
| Brakes | 1.1.11. Rigid brake pipes | (b) Leaking brake pipe or connection | (ii) on a hydraulic system | Dangerous |
| Brakes | 1.1.12. Flexible brake hoses | (a) Brake hose damaged and likely to fail | N/A | Dangerous |
| Brakes | 1.1.12. Flexible brake hoses | (c) Brake hoses or connections leaking on | (ii) hydraulic systems | Dangerous |
| Brakes | 1.1.12. Flexible brake hoses | (f) Brake hose ferrules | (ii) excessively corroded and likely to fail | Dangerous |
| Brakes | 1.1.13. Brake linings and pads | (a) Brake lining or pad | (ii) worn below 1.5mm | Dangerous |
| Brakes | 1.1.13. Brake linings and pads | (c) Brake lining or pad missing or incorrectly mounted | N/A | Dangerous |
| Brakes | 1.1.14. Brake discs and drums | (a) Brake disc or drum | (ii) insecure, fractured or otherwise likely to fail | Dangerous |
| Brakes | 1.1.14. Brake discs and drums | (c) Missing | N/A | Dangerous |
| Brakes | 1.1.16. Brake actuators - including spring brakes, hydraulic cylinders and callipers | (a) Actuator cracked or damaged and | (ii) braking performance affected | Dangerous |
| Brakes | 1.1.16. Brake actuators - including spring brakes, hydraulic cylinders and callipers | (b) Actuator leaking and | (ii) braking performance affected | Dangerous |
| Brakes | 1.1.16. Brake actuators - including spring brakes, hydraulic cylinders and callipers | (c) Actuator insecure or inadequately mounted and | (ii) braking performance affected | Dangerous |
| Brakes | 1.1.16. Brake actuators - including spring brakes, hydraulic cylinders and callipers | (d) Actuator | (ii) excessively corroded and likely to crack | Dangerous |
| Brakes | 1.1.16. Brake actuators - including spring brakes, hydraulic cylinders and callipers | (e) Actuator has | (ii) no reserve travel and braking performance affected | Dangerous |
| Brakes | 1.1.17. Load sensing valve | (c) Load sensing valve seized or inoperative and | (ii) ABS not fitted or inoperative | Dangerous |
| Brakes | 1.1.17. Load sensing valve | (d) Load sensing valve missing where fitted as standard | N/A | Dangerous |
| Brakes | 1.1.21. Complete braking system | (a) Other braking system (e.g. antifreeze pump, air dryer etc.) component damaged or corroded | (ii) leaking and system functionality adversely affected | Dangerous |
| Brakes | 1.1.21. Complete braking system | (d) Braking system component modification | (ii) adversely affecting braking performance | Dangerous |
| Brakes | 1.1.21. Complete braking system | (e) The strength or continuity of the load bearing structure within 30cm of any braking system actuation component mounting (a prescribed area) | (ii) is so weakened that the functionality of the braking system is affected | Dangerous |
| Brakes | 1.2.1. Performance | (a) Braking effort | (ii) not recording at a wheel | Dangerous |
| Brakes | 1.2.1. Performance | (b) Brakes imbalance across an axle such that | (ii) the braking effort from any wheel is less than 50% of the maximum effort recorded from the other wheel on a steered axle | Dangerous |
| Brakes | 1.2.2. Efficiency | (a) Service brake efficiency | (ii) less than 50% of the required value | Dangerous |
| Brakes | 1.3.1. Performance | (a) Braking effort | (ii) not recording at any wheel | Dangerous |
| Brakes | 1.3.1. Performance | (b) Brakes imbalance across an axle such that | (ii) the braking effort from any wheel is less than 50% of the maximum effort recorded from the other wheel on a steered axle | Dangerous |
| Brakes | 1.3.2. Efficiency | (a) Parking brake efficiency | (ii) less than 50% of the required value | Dangerous |
| Brakes | 1.4.2. Efficiency | (a) Parking brake efficiency | (ii) less than 50% of the required value | Dangerous |
Brakes – What to Do If You Fail for This Issue
If your car fails its MOT due to a dangerous brake fault, do not drive the vehicle under any circumstances.
Contact the garage to arrange immediate repairs, or request vehicle recovery if needed.
Driving with brake defects can lead to fines, points on your licence, or serious accidents. Once repaired, you’ll need to book a partial retest at the same MOT station.
Brakes – Symptoms to Watch For
- Spongy or soft brake pedal feel
- Grinding or squealing noises when braking
- Increased stopping distance
- Pulling to one side under braking
- Dashboard brake warning light illuminated
If you notice any of these signs, have your brakes checked immediately. Ignoring them could lead to a dangerous MOT failure — or worse, a real-world accident.