What is Brake Fluid?

Brake fluid isn’t the most exciting part of car maintenance, but it is essential for keeping your car safe and roadworthy. If your brakes feel a bit spongy or you’re wondering what that warning light means, then this guide is for you. We’re here to answer all your questions and keep you stopping safely: what is brake fluid, why do you need to change your brake fluid, how often should you change your brake fluid, and more.  

What Is Brake Fluid? 

Brake fluid is a hydraulic liquid that plays a very important role in your cars braking system. When you press the brake, this fluid transfers that force into pressure that slows your car down... Without it, you’d just be pushing your foot into thin air, which isn’t the most ideal scenario when the lights turn red.  

Another job that brake fluid ticks off is it acts as a lubricant and helps prevent corrosion in key components like brake lines (these are how your brake fluid travels) and callipers (these sit over your brake discs and squeeze them when you brake, using the pressure from that fluid in the brake lines).  

Most brake fluids are either glycol-ether or silicone-based and are specially formulated to handle the high heat generated when you use your brakes – especially when you’re driving downhill or stopping suddenly.  

Why Does Brake Fluid Need Changing? 

Brake fluid absorbs moisture from the air over time which lowers its boiling point and makes it less effective, often resulting in longer stopping distances and even brake failure if left too long. Changing it regularly ensures your brakes respond properly when you need them most. Think of it like changing your oil or topping up your coolant – routine care that protects bigger, more expensive parts from wearing out or getting damaged. 

How Often Should It Be Changed? 

Brake fluid should be changed every two years or 24,000 miles, whichever comes first. But some vehicles might need it more often depending on the make, model, and driving conditions, so it’s best to check your owner’s manual or ask our service team for advice. It can be included in your annual service or MOT too. 

What Does a Brake Fluid Change Involve? 

A brake fluid change is done by a professional mechanic, who will: 

• Locate the brake fluid reservoir under the bonnet 
• Use a siphon or pump to remove the old fluid 
• Refill with the correct brake fluid for the car 
• Check for leaks or signs of damage in the system 

The process takes less than an hour and makes a huge difference in braking performance. This isn’t really a DIY job.  

How Much Does It Cost? 

A brake fluid change can start from £80, depending on the type of vehicle, but luxury or higher performing models can cost quite a bit more. CTA Call us for a quote. 

But this can be a small price to pay, considering it could cost far more in the long run – damaged brake lines, corroded callipers, or worse, an unresponsive brake.  

Should You Top Up Your Brake Fluid? 

Unlike screen wash or oil, brake fluid doesn’t usually need topping up regularly. In fact, if your brake fluid level is low, it could be a sign of a bigger issue - like worn brake pads or even a leak in the system. 

That said, it’s still worth checking your brake fluid level now and then (especially if a warning light comes on, or your brakes feel less responsive). You can do this by looking at the brake fluid reservoir under the bonnet—there’s usually a “MIN” and “MAX” line marked on it. If it’s below “MIN,” it’s time to get it checked out. 

⚠️ Important: Never just keep topping it up without finding out why it's low. Brake fluid doesn’t just vanish - so if it’s dropping, your brakes might not be safe, and it’s best to get a professional to take a look! 

Need Your Brakes Checked? 

If it’s been a while since your last service, or your brakes feel off, don’t wait. Contact SERE Motors Belfast or Lisburn to chat with our expert team. 

We’re here to keep your car safe, smooth, and ready for anything the road throws at you.