Brake fluid colour is usually clear or light amber but can also have a dark yellow tint pigmentation.
This occurs when the brake fluid absorbs water from the air due to repeated use of moisture in its system. If your car seems to require more brake pedal pressure than normal, you may have a brake fluid leak or worn brake pads. Some manufacturers recommend replacing brake fluid every two years, while others specify every four years. It's possible for the colour of the brake fluid to change from light amber to dark brown over time even if no leaks are present; this is especially true if it's subjected to extreme heat or cold during storage or usage. The most reliable way to tell if there might be a problem with your brakes is to have them checked by a qualified mechanic. If your brake fluid is dark brown in colour, have your brakes inspected as soon as possible. If there isn't a problem with the brakes themselves, you probably need to get the fluid flushed and replaced.
In a brake flush, the technician will open the fluid reservoir and remove about half of the old fluid. A suction tool then pulls out any more remaining in the lines and calipers before fresh fluid is added back to top off the system. This reduces or eliminates moisture from entering your brake lines.
Brake fluids are a mixture of water and ethylene glycol, which lowers the boiling point of water to allow for safe braking at high temperatures. The ethylene glycol both lubricates parts inside the braking system as well as lowers surface tension so that pressure on the foot brake pedal will push it down with less effort.
When a driver puts pressure on the brake pedal, the vacuum power booster system activates a master cylinder. The pressurised brake fluid pushes brake fluid into the brake line all the way to the brake parts that connect to the wheels, pushing pistons that apply pressure to the rotors or discs through the brake pads.
The friction action of the brake pads stops the vehicle. The brake system works with the ABS unit.There are four types of brake fluids in Australia generally used for cars, motorcycles, or any other vehicle that uses hydraulic braking systems.
This type is also known as mineral oil and DOT3 / DOT4 fluid. It's the most common type found in passenger vehicles, trucks, and motorcycles.
Also called mineral oil with polyol ester added, it's different because it has a lower boiling point than standard brake fluid but often costs more.
This is low-viscosity mineral oil with some alcohol-based additives included to help prevent corrosion and deposits from building up on components inside a braking system. OAT brake fluids are very popular in later model vehicles.
Contains a combination of low viscosity oils and synthetic fluids.
There are different brake fluids for different types of vehicles, so it's important to know what type you need. Generally, you will find brake fluid labels with the initials DOT. Cars used in plains and under normal driving conditions will comfortably use DOT 3 brake fluids. In higher altitudes conditions, DOT4 is recommended. DOT 5 and DOT5.1 brake fluid is recommended for performance-based vehicles and race cars. DOT3 and 4 brake fluids are poly glycol-based, whereas DOT5 and 5.1 are silicone-based. You can only mix brake fluids that have similar characteristics. As such, you can mix DOT 3 and 4 but cannot mix this category with DOT 5s. If you're not sure which type of brake fluid is correct for your vehicle, consult an expert or check the manufacturer's manual for more information.
Using any other type of brake fluid than what is recommended by your car's manufacturer can cause deterioration and even damage to parts inside the braking system. Using the wrong brake fluid will alter the performance of a braking system, which can cause brake failure. Contaminated brake fluid can also cause corrosion of the brake lines, damage seals, or clog valves. Some damages may be irreversible, even with a brake fluid flush.
If you neglect to change your brake fluid over time, it can cause permanent damage to your brake system or lead to failure of either your master or wheel cylinders resulting in brakes that do not work. The absorption of moisture contaminates brake oil. This affects the brake fluid composition, altering important characteristics like the boiling point, viscosity, and corrosion resistance. Opening the brake cap for long periods can also lead to dirt or grime mixing with the fluid. All these factors lead to dirty brake fluid. Always check or have your mechanic check any changes in brake fluid colour, which may be a sign of old or contaminated brake fluid.
The frequency of changing your brake fluid largely depends on what type of driving you do, how many miles are driven each year, and also what the weather is like where you live. If you drive in an area where it's very hot or very cold, or if your brake system deals with a lot of water through rain and car washes then it's a good idea to change your brake fluid more regularly. Some brake fluid manufacturers recommend a change every two years. Many drivers find it necessary to change old to new brake fluid every 4 to five years. Different car makers have different recommendations for brake fluid replacement. Check your user manual for details. If you notice dark brake fluid with a semblance to used motor oil colour, that's a sign you need to replace the old brake oils with new brake fluid. Again, if the brake pedal feels soft and there are no visible leakages, it may be due to moisture contamination affecting the viscosity performance of the brake fluid.
If the colour of your brake fluid has changed from its original colour, or if you notice any leaks under the hood near the brake system, this could indicate that your brake fluid should be changed. If there are visible signs of corrosion on components inside your braking system, especially near the master cylinder, change your brake fluid immediately.
Check the brake fluid reservoir located in the engine bay. If it has a clear plastic cap, remove the cap and check the fluid level. If it's dark or murky, you should change your brake fluid immediately. The brake fluid level in the reservoir should not be lower than "min" or higher than "max" under any circumstances. If it is, you may have a leak in your braking system and will need to consult your manufacturer's manual to find out which type of brake fluid is compatible with your vehicle and how to add more if necessary.
If the brake fluid is down to the minimum level, you can top it up using new brake fluid. Make sure that you use the correct type of brake fluid as outlined in your owner's manual, and follow any specific instructions or precautions listed on your car's handbook. After adding more brake fluid, check the reservoir again and keep checking your brakes every few days until they feel normal again.
Also, ensure you do not have leaking brake fluid lines. If there are any leaks, you will notice wet brake lines or wetness at the pistons or cylinder sections.
The South Australian state government has a handy information sheet to brakes and braking modifications.