How to check and change your brake fluid

How to check and change your brake fluid

Knowing how to check and change your brake fluid is just as important as checking your car’s engine oil and knowing how to change that.

Your vehicle is a well-oiled machine (hopefully…) that takes many different components working in harmony to run properly.

Therefore no one area is more important than the other, which is why in our series of ‘how to’ guides we’re running through how to check and change every important component on your car.

We’ve already told you why checking your brake fluid is important in the past, but now we’re going to tell you how to check and change one of the most important systems on your vehicle when it comes to safety.

In fact, your vehicle’s brakes are its biggest safety feature – that’s why it’s important to maintain they’re perfect working condition. And brake fluid can often be a culprit for faults.


To check your brake fluid level you’ll first need to open the bonnet and identify the correct reservoir – generally this will have a similar symbol to your car’s parking brake light, minus the exclamation mark.

If you’re not sure what this look like, turn the car on with the handbrake applied and look for a dashboard warning light – it’ll be a circle with two small arcs on either side of it.

Once you’ve found the right reservoir, locate the ‘Min’ and ‘Max’ scale on the side of the plastic tub – this should be easily visible as it’s the only way to assess how much fluid is in the tank.

If it’s under the minimum, do not drive your car until you top up the level, as you could be putting you and your passengers at risk. If you carry out regular checks – say, once a month – it shouldn’t get to the stage where the level drops below the minimum mark anyway.

Topping up your brake fluid (c) Newspress


Once you’ve located the brake fluid reservoir and decided it needs a top-up, you’ll need to make sure you get the right grade of brake fluid. The best way to do this is consult your vehicle handbook or phone your local dealer for help.

In most road cars it will usually be a solution called DOT 3, DOT 4, or DOT 5.1 – these are all based on a chemical called glycol, which is resistant to compression and boiling, as well as other chemical properties, such as not mixing with water.

In some cases it may be DOT 5 – this is a silicon-based fluid and must not be mixed with any of the above. That’s why it’s important to accurately track down which type of fluid you have in your car.

Once you’ve picked up the right fluid, it’s simply a case of topping the reservoir up to the ‘Max’ line. However, if you need to completely replace the brake fluid in the system, bleeding the lines, it is a more in-depth job.


The most important tip here is to make sure you are confident in carrying out this task. If you’re not, pay a professional to do it for you.

Start by safely jacking the car up and securing it on properly rated axle stands. Take one wheel off at a time and locate the brake caliper bleed nipple – this will be a small (8mm) octagonal nut on the body of the brake caliper itself.

Loosen this off, but not all the way – you’ll need to continually open and close it throughout the brake bleeding procedure.

There are two ways to now bleed your car’s brakes. You can buy a ‘power bleeder’ (effectively a pump with a non-return valve in-line to stop brake fluid flowing backwards and air entering the system) and fit it to the bleed nipple, or you can use a length of narrow-gauge hose over the nipple and get a friend to sit in the car to pump the brake pedal.

This will force fluid through the circuit just like the pump on a power bleeder, but can be more time consuming.

Using the first method, it’s a simple case of pumping the handle to draw fresh brake fluid through the system – make sure you keep an eye on the reservoir, as the fluid level will drop. Keep topping it up so no air makes its way into the lines, we’ll tell you why in a moment.

If you’re doing it the old fashioned way, get your friend to pump the pedal first, building up some pressure, tell them to keep their foot on the brakes then open the bleed valve so the brake fluid is squeezed out. Close the bleed nipple and only then tell your friend to release the brake.

Repeat this process – keeping an eye on the fluid level – until fresh fluid is drawn through the system. Repeat for every corner.

Make sure you DO NOT forget to tighten the bleed nipples when finished.

How to check and change your brake fluid (c) Newspress


It’s important that no air enters the brake lines when you’re bleeding the system. Brake fluid gets hot during operation and any air (or water for that mater) in the lines will expand, reducing your car’s braking performance and giving a spongy feeling to the pedal.


Brake fluid is very slippery indeed so make sure you clean any spilt solution off your calipers.

If it has dripped onto the discs or pads, you will have to take those off for safety reasons and clean them with brake cleaner to restore they’re full performance.

You can’t just tip brake fluid down the drain either – it’s an extremely toxic chemical, which can damage eco systems, so don’t pour it into the flowerbeds. Read the back of the bottle to find out how to dispose of it in an environmentally friendly way, or take it to your local council waste centre to see if they can help.


Always check you have a solid-feeling brake pedal before you take your car out for a test on the open road. On your driveway just try rolling the car and pushing the brakes to check they work. Safety is paramount when performing jobs on your car – especially on its braking system – so double-check everything is tight and in working order.

From there, perform a gentle test drive, come back and double-check everything again – then all that’s left to do is go and have some fun with your fresh, new, feelsome brakes.

How often do you check your brake fluid? Do you top it up and bleed your vehicle’s brakes yourself? If so, we want to know if you’ve got any top brake bleeding tips you use without fail. Why not let us know on twitter @twwhiteandsons or on our Facebook page.

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