In this guide, we examine brake fluid leak causes, and what you should do if you notice brake fluid leaking from various components.
Identifying a brake fluid leak
There are a range of causes of brake fluid leaks, including damage to brake components and general wear, rusting and pitting. If your dashboard brake fluid indicator is lit and your reservoir is low despite you topping up your fluid, there’s a high chance your brake hydraulic system – usually closed – is compromised.
Typically, brake fluid leaks are identified by a pool of light yellow or brown fluid beneath your vehicle.
When depressed, the brake pedal may also feel spongy or soft – this can be due to air entering the braking system via a leak.
Leaks are usually due to issues with the master cylinder, ABS module, brake line, bleeder valve, rotor, drum, pistons, or general brake assemblies, so checking which component is above the leak can sometimes signify the source.
To find the leak, safely jack up your vehicle, block the wheels and engage the parking brake in order to conduct a thorough visual check beneath your vehicle.
If the leak is light or difficult to locate, place newspaper beneath the car, then, with the car stationery and engine off, press the brake pedal repeatedly. This should force out brake fluid through any leaking components, which will show up on the newspaper or be visible upon inspection.
Check that the reservoir lid is tightly fastened – this can also be a source of leakage.
Internal leaks can also occur. In this case, fluid can leak from one component into another without any symptoms such as pools of brake fluid manifesting beneath your car. If your fluid level keeps falling despite top-ups and you cannot see any obvious source or indication of leakage, refrain from driving the vehicle and visit your mechanic as soon as possible.
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Fixing a leak is entirely dependent on its source, so if you are unsure which failed component is causing the leak or are not experienced or confident working on your car, always visit a trained mechanic and have them perform the repairs.
To perform fixes yourself, you will need:
A car jack
Parts (dependent on which component you are repairing)
Car maintenance tools (noted in part-specific repair kits).
Your vehicle’s master cylinder should be located below the brake fluid reservoir. If it is worn, broken, or leaking, you should purchase a master cylinder rebuild kit. The kit should come with detailed instructions on how to remove and rebuild a new master cylinder.
The same is true for your wheel cylinders and caliper pistons, both located within the wheel assembly. Take care to check your caliper bolts too – these may simply need tightening.
Brake hoses are located behind each wheel. If they are damaged and leaking, it’s a case of getting new hoses and replacing them.
Located beneath your vehicle, if your brake lines are leaking then the entirety of the lines will need replacing with new metal tubing, utilising a pipe bender. This can be a complex job and you will need to adjust the torque of the lines to levels specified by your vehicle’s manufacturer.
If your ABS module or pump is visibly leaking, you should visit a mechanic to effectively remedy the problem.