How to top up brake fluid (6 easy steps)

If you’ve noticed your brake warning light come on or your brake pedal feels a little softer than usual, low brake fluid could be the reason. The good news is that topping up brake fluid is usually quick and straightforward.  

In this guide, we’ll explain how to top up brake fluid step by step, how to check your brake fluid level, and when it’s time to book in with Merityre instead of doing it yourself.

 

What Does Brake Fluid Actually Do? 

Brake fluid is a hydraulic fluid. When you press the brake pedal, it transfers force from your foot to the brake components connected to the wheels. Without enough brake fluid, your car simply will not brake effectively. 

Low brake fluid can lead to: 

• a soft or spongy brake pedal 

• increased stopping distances 

• brake warning light on the dashboard 

• reduced braking performance 

This is not something you can ignore. 

 

How to Safely Top Up Your Brake Fluid 

If your brake fluid level is low, you can top it up yourself, but it is important to follow the correct steps to stay safe and avoid damaging your braking system. 

 

Step 1: Park Safely and Let the Engine Cool 

Park your car on level ground and switch the engine off. Engage the handbrake and allow the engine to cool before opening the bonnet. 

Brake fluid sits in a small reservoir in the engine bay, usually towards the back near the driver’s side. 

 

Step 2: Locate the Brake Fluid Reservoir 

Look for a small, translucent plastic tank with a cap labelled “Brake Fluid” or “DOT 4”. If unsure, check your vehicle’s handbook to find the correct location. 

The reservoir will have minimum and maximum markings on the side. Because the plastic is usually semi-transparent, you can often see the fluid level without removing the cap. 

If the level is below the minimum line, it needs topping up. 

 

Step 3: Check You Have the Correct Type of Brake Fluid 

Before opening the cap, check your vehicle handbook to confirm you have the correct brake fluid type. Most modern cars use DOT 4, but some use DOT 3 or DOT 5.1. 

Never mix different types unless your manufacturer confirms it’s safe to do so. 

Using the wrong fluid can damage your braking system. 

 

Step 4: Clean Around the Cap 

Brake systems must stay clean. Even small amounts of dirt can cause problems. 

Wipe around the reservoir cap with a clean cloth before removing it. This prevents debris from falling into the system. 

 

Step 5: Carefully Top Up the Brake Fluid 

Wear gloves to protect your skin from any contact with the brake fluid 

Unscrew the cap slowly. 

Insert a funnel into the top of the brake fluid reservoir and pour the brake fluid in steadily, stopping when it reaches just below the maximum line. Do not overfill it. 

Brake fluid is corrosive, so avoid spilling it on painted surfaces. If you do spill any, wipe it off immediately. 

Once topped up, securely refit the cap. 

 

Step 6: Check the Brake Pedal 

After closing the bonnet, press the brake pedal a few times. It should feel firm and responsive. 

If the pedal still feels soft, sinks to the floor, or the warning light remains on, do not continue driving. This could indicate a leak or air in the system. 

 

Why Was the Brake Fluid Low? 

Brake fluid does not simply “get used up” like fuel. If it’s low, there’s usually a reason: 

• Worn brake pads 

• A leak in the braking system 

• Damaged brake lines 

• Faulty seals 

If you find yourself topping up regularly, that’s a red flag. The system needs inspecting. 

 

When to Book a Brake Check Instead 

Topping up brake fluid is fine as a short-term fix. But you should book a professional inspection if: 

• The brake warning light stays on 

• You notice fluid under the car 

• Braking feels inconsistent 

• It has been over two years since your last brake fluid change 

Brake fluid absorbs moisture over time, which reduces its effectiveness. Most manufacturers recommend replacing it every two years. Discover the signs of brake failure from our dedicated brakes page. 

At Merityre, trained technicians can check your brake system properly, including brake pads, discs, and fluid condition, so you can drive with confidence. 

Book your free brake check at your nearest Merityre garage across South East England today.