How much brake fluid does a car need and how to add it
While we all know the importance of brakes, it can be easy to forget the maintenance brakes require to keep them in top condition.
Unless your car is vintage, you are more than likely to have hydraulic brakes. In addition to the more obvious components, such as the disks and pads, you also have the hydraulic brake lines containing fluid which is central to the mechanism. Unfortunately, this fluid doesn't last forever and a range of driving conditions can affect its performance. This is why years of experience tell us that checking the fluid regularly and knowing how to top it up is an essential part of your car's routine maintenance.
How can I tell if I need to change the brake fluid?
In the driver's seat, the first indicator you'll notice is a "soft" feel to the brakes. This is because the fluid is no longer able to create a sufficient level of pressure, rendering the hydraulic system ineffective. The real reason for this is usually that air or water has entered into the hydraulic cylinder or excessive heat has boiled the fluid to create air bubbles that spoil the system.
To get a little more technical, brake fluid is hygroscopic. This means it absorbs moisture from the air, which will happen gradually over time. The greater proportion of moisture in the fluid, the lower the boiling point will be of that fluid. This, in turn, increases the chance of it boiling and creating air bubbles that render the fluid compressible and compromise the braking system.
In our experience, for most drivers this will happen after a period of prolonged braking, but it can also occur in any kind of sport or track driving where higher speeds and temperatures make it likely the fluid will boil and lead to brake fade. In each situation, the only solution is to replenish the braking system with new fluid. Spoiled fluid will have a burnt smell and will look darkened or black in colour. This should always be your signal to change the fluid.
If you use the wrong size battery, this could cause changes in the flow of electrical currents, resulting in power surges that can damage the onboard computers or other components.
How to add brake fluid
First of all, we need to advise you that changing your brake fluid is ordinarily a two-person job and should always be handled by professionals unless you are highly experienced. One person needs to press and release the brake pedal while the other controls the flushing of the old fluid in order to prevent any new air from entering the system.
You will need to remove as much old fluid as possible from the master cylinder normally found under the bonnet. Remember to dispose of this safely, never in regular landfill or down the drain, as the fluid is noxious.
Next, you'll need to access the brakes themselves, which will require lifting the car with all the wheels removed. Very few people have access to this kind of equipment, so consider whether it might be easier to take to your local Protyre garage. Once the brakes are accessible, fill up the master cylinder with fresh brake fluid so that you'll be filling the hydraulic lines with new fluid as you flush out the old fluid.
The minimum amount of brake fluid you'll need will depend on your car, so always take a look at your vehicle's manual. As a rough guide, 500ml should be suitable for flushing most hydraulic brake systems, but if you're replacing burned or spoiled fluid, then you may need roughly a litre in order to fill the system entirely with fresh fluid.
Flushing the brakes
Finally, it is time to flush the system. This is where the second person comes in. Locate the bleed nipple on the brake calliper and connect this to a small pipe or hose to direct the old fluid into a suitable container.
One person will need to press on the brake pedal while the other opens and closes the bleed nipple. You want to open the bleed nipple as the brake is being pressed down, then make sure to close the nipple as the pedal is lifted back up. This is to prevent drawing new air into the system as the brake pedal is relaxed, which will create the same problems as before. Keep going until new, clear brake fluid with no air bubbles comes through the nipple. Finally, top up the fluid level in the master cylinder as necessary.
Professional help when you need it
Brakes are a vital part of any vehicle, but changing the brake fluid can be a time-consuming task and requires knowledge, equipment and expertise. Years of experience tell us that it is usually safer, easier, quicker, and more efficient to seek professional help.
Our tyre professionals aren't just expects on quality tyre products such as Pirelli and Bridgestone. They are also on hand at our nationwide network of local garages to take the appropriate action with your braking system. They have the training and technical know-how to identify whether the fluid or another underlying reason is causing braking problems.
With free vehicle checks available to book online today, why not consider dropping in or giving our qualified fitters a call to see how we can help?
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