For brake fluids, the boiling points and viscosity matter. Boiling point actually means the temperature at which the brake fluid starts to boil. The heat that is generated during braking is transferred to the brake lines. This can cause the brake fluid to heat up. If it starts to boil, this results in a sharp drop in braking performance, as the formation of vapor bubbles reduces the hydraulic pressure. A distinction is made between the dry and wet boiling points.
The dry boiling point refers to the brake fluid in its original state when it is very freshly filled into the brake lines. Over time, the brake fluid absorbs water via the brake lines and thus "dilutes" somewhat. This also lowers the boiling point, as water boils faster than the brake fluid. This is then referred to as the wet boiling point. The higher both values are, the better the brake fluid. The water content should be checked once a year, as the brake fluid should be replaced from a content of 3.5%.
The higher the value of the viscositiy, the more viscous the brake fluid. In vehicles with ESP systems, the value should be as low as possible, as these systems sometimes have tiny openings through which the fluid must flow. The thinner it is, the easier it is and the faster the brake system can react to the pressure changes.
Viscosity and boiling points have been divided into different types by the US Department of Transportation. These begin with DOT (=Department of Transportation) such as the brake fluid DOT 4 or DOT 5.1. The brake fluid is divided into the following types:
brake fluid DOT 3:
brake fluid DOT 4:
brake fluid DOT 5.1:
In addition to viscosity and boiling points, other requirements are placed on brake fluids besides temperature resistance. On the one hand, the fluid must not be affected by temperature fluctuations, and on the other hand, it must contain corrosion protection to delay wear of the components concerned.
In addition to an excessively high water content, small leaks, for example due to porous brake lines, can lead to a loss of brake fluid. In both cases, this has an impact on braking performance, which decreases as a result. For this reason, the ADAC recommends checking the brake fluid once a year and carrying out a complete brake fluid change every 2 years.This applies above all to vehicles that have been driven little in that time and older vehicles that are on the road with DOT 3. But also with newer vehicles a regular check of the water content and the filling level is necessary. Too much water in the brake fluid can promote the formation of rust, which should be avoided.
When changing brake fluid, it should be noted that air can get into the brake system, which must be removed again by bleeding before operation. In addition, brake fluid should be handled with care. It is not only toxic, but also corrosive, which is why it should not come into contact with the skin, paint or other components in the engine compartment. If it does happen, it is important to clean the areas immediately. The old brake fluid and the container should then be disposed of properly. Both are considered hazardous waste. If this is too tricky, it is best to have the brake fluid changed by a workshop.
When buying brake fluid depends on the correct type of fluid. Whether the brake fluid DOT 4, DOT 5.1 or another type is correct for your vehicle, you can find out in the owner's manual of your car. On some vehicles, the DOT specification is also indicated on the cap of the expansion tank. Basically, the types should not be mixed, as this changes the boiling points and viscosities.
In addition to the right types, high-quality brake fluids also contain the above-mentioned protective components against wear and corrosion. Therefore, it is recommended to rely on branded goods. Namable manufacturers of brake fluids that we carry are, for example:
With the brake fluids it is not necessary to buy the original goods of the vehicle manufacturers, because they do not produce the fluids themselves, but also fall back on brand manufacturers. The brake fluids offered by us also still convince with a favorable price.
In addition, when buying brake fluid is still to pay attention to the required amount. It is not advisable to stock up and buy more than fits into the brake system. As soon as the bottle or canister is opened, it draws water little by little, with which the brake fluid there already diluted and thus starts with worse conditions. You can also find the indication of the quantity in the manual of the vehicle.
If you are unsure which brake fluid to buy or there are any other questions about it, please feel free to contact our customer service with the vehicle details.
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