Why Your Brake Fluid Needs More Attention Than You Think

When it comes to car maintenance, most drivers know to check their tyres, change the oil, and top up their washer fluid. But there’s one vital fluid quietly doing its job behind the scenes — and neglecting it could seriously impact your safety: brake fluid.

Despite being one of the most critical elements in your car’s braking system, brake fluid is often overlooked. And in the UK, ignoring it can mean the difference between passing or failing your MOT — or worse, losing braking performance when you need it most.

In this blog, we’ll explore what brake fluid actually does, how it degrades, how to spot issues, and why it deserves far more attention than it typically gets.

? What Is Brake Fluid and Why Does It Matter?

Brake fluid is a hydraulic fluid. Its main job is to transfer force from your brake pedal to the brake callipers or drums. When you press the pedal, the fluid transmits that force through a network of brake lines to apply pressure to your brake pads or shoes — slowing your vehicle down.

The pressure has to be instant and consistent. That means the fluid must be non-compressible and able to operate across a wide range of temperatures.

But here’s the problem: brake fluid is hygroscopic — it absorbs moisture from the air. Over time, that moisture builds up inside your brake system, lowering the fluid’s boiling point and increasing the risk of corrosion inside brake lines and master cylinders.

? What Happens When Brake Fluid Goes Bad?

Brake fluid degrades gradually, and because it’s not visible in your day-to-day checks, it’s easy to forget. But the signs are there if you know what to look for:

• Spongy or soft brake pedal feel

• Longer stopping distances

• Discoloured or dark fluid in the reservoir

• Squeaking or fading brakes under pressure

As moisture increases in the system, your brake fluid’s boiling point drops. This means during heavy braking (especially downhill or when towing), the fluid can boil inside the lines, causing a sudden loss of braking power known as brake fade.

And while this may sound extreme, it’s not uncommon — particularly in older vehicles or those that haven’t had a fluid change in years.

? MOT Failure Risk & Why It’s Often Missed

Brake fluid isn’t just a safety issue — it’s also an MOT concern. While MOT testers don’t open the reservoir or test fluid directly, they are required to fail vehicles with:

• Spongy or ineffective brakes

• Low fluid levels

• Corroded brake lines (a symptom of moisture-laden fluid)

At Brede Garage, we often see MOT fails where the root cause traces back to poor brake fluid condition — even though it doesn’t trigger a dashboard warning light.

? How Brake Fluid Is Tested Professionally

At Brede Garage, we use specialist tools to check brake fluid condition, including:

• Boiling point testers to see if your fluid is still within spec

• Moisture content meters to measure water absorption

• Visual inspections for signs of contamination or ageing

If the boiling point has dropped too low, or the fluid is visibly contaminated, we’ll recommend a full system flush with fresh DOT-approved fluid.

We recommend changing your brake fluid every 2 years — or sooner if you tow, drive in hills, or do high mileage. It’s a quick and affordable way to stay safe and compliant.

? Brake Fluid Myths — Busted

There are plenty of misconceptions floating around about brake fluid:

• “It only needs topping up, not changing.” Wrong. Fluid level may drop due to pad wear, but the real danger is moisture buildup.

• “It lasts the life of the vehicle.” Absolutely not. Like oil or coolant, brake fluid degrades with time and heat.

• “I’ll know when there’s a problem.” Possibly — but by then, it could be dangerous.

These myths lead many car owners to delay a brake fluid change far beyond what’s safe.

? Summary: Why This Matters

Brake fluid isn’t glamorous. It doesn’t get topped up at the fuel station. But without it, your brakes simply wouldn’t work — and over time, poor fluid could put you, your passengers, and other road users at risk.

If you can’t remember the last time your brake fluid was checked or changed, it’s probably overdue.

? Book a brake fluid inspection today at Brede Garage — and stop taking chances with your stopping power.