When preparing for your MOT, most UK drivers focus on tyres, lights, and brakes — but one crucial component is often overlooked: brake fluid. Although it may seem like a small detail, the condition of your brake fluid can significantly impact your MOT result. Poor-quality or contaminated fluid can reduce braking performance, increase stopping distances, and in some cases, contribute to an MOT failure.
In this guide, we explain why brake fluid matters, how it affects MOT pass rates, and what you can do to ensure your vehicle remains safe and roadworthy.
Brake fluid plays an essential role in your vehicle’s hydraulic braking system. When you press the brake pedal, the fluid transfers pressure to the brake components, helping the car slow down or stop. Over time, brake fluid absorbs moisture from the air, reducing its boiling point and overall effectiveness.
During an MOT, testers will check:
While the MOT does not explicitly require a brake fluid test (such as a boiling point check), any issue affecting braking performance can directly lead to a fail.
Brake fluid naturally deteriorates over several factors:
Brake fluid is hygroscopic, meaning it absorbs water. High water content can cause:
Dirt, rust, or rubber particles can enter the system, causing:
Low fluid levels can be caused by leaks or worn brake pads. This can trigger a dashboard warning light — an instant MOT fail.
While brake fluid age alone doesn’t fail an MOT, the symptoms of degraded fluid can. These include:
Any of these issues may result in a fail or advisory.
Most manufacturers recommend changing brake fluid every 2 years, but this varies by vehicle. Regular services often include a brake fluid boiling point test to check for water content and contamination.
Keeping fluid fresh not only protects your safety but also improves your chances of passing your MOT the first time.
Before booking your test, check your MOT history and due date quickly at CheckMot.com. Staying informed helps you prepare for potential issues before they become MOT failures.
Not directly. However, anything affecting braking performance — such as leaks or poor responsiveness — can cause a failure.
Yes. If your brake warning light is on or your brake system shows signs of low fluid, the vehicle will fail.
Signs include a spongy pedal, longer stopping distances, or dark/dirty fluid in the reservoir.
Brake fluid should not need regular topping up. Frequent drops in level indicate a leak or worn pads and require immediate attention.