General brake fluid - BB00.40-P-0330-01A

These specifications are valid for the Mercedes-Benz and smart brands. 

General 

The brake fluid in the brake system and in the hydraulic clutch operating system fulfills hydraulic tasks. Due to the high heat build-up during braking, these tasks can only be fulfilled by brake fluids which comply with all of today's technical requirements in terms of their various properties (viscosity-temperature-characteristic, boiling point, corrosion protection, oxidation resistance, etc.).

The most important properties which a brake fluid must exhibit are:

• High boiling point, to ensure that the brake fluid does not form vapor locks at high temperatures. Vapor locks reduce the operating pressure and thus the braking effect and may ultimately lead to brake failure.
• The boiling point should remain as constant as possible throughout the duration of use of the coolant and not drop under varying atmospheric influences or operating conditions (pressure, temperature), i.e. the "wet boiling point" should be as high as possible.
• Low compressibility, in particular at high temperatures.
• The low-temperature characteristic of the fluid - even when at 40°C - must permit operation, i.e. primarily, the viscosity must not become too high in the cold.
• Compatibility with the materials used in the brake units and clutch operating systems, e.g. the rubber boots or any other seal materials (elastomers) included in the brake components may only swell to a controlled extent, any shrinkage must be avoided.
• Sufficient corrosion protection for all metals present in the brake system.

The brake fluids released for use in MB vehicle models are listed on Sheet 331.0. These brake fluids not only comply with our requirements, but also those of the US safety specifications FMVSS 116, DOT 4. The released "DOT 4 plus" brake fluids (internal designation) are more advanced DOT 4 brake fluids with higher wet boiling point, standard change interval: 2 years. In order to be able to comply with this useful period without any problem, we strongly advise the use of released products as per Sheet 331.0, during the warranty phase this is a precondition for any acceptance of customer claims.

The brake fluid listed on Sheet 331.1 "DOT 4 Type 200" is released for special applications in the UNIMOG range with more stringent thermal requirements. For this type of use, a brake fluid change interval of 1 year must be adhered to.

Handling brake fluid 

Brake fluid based on polyhydric alcohols in oligomer or polymer form and/or their

Esters are hygroscopic and thus absorbs moisture from the air. Water, however, reduces the boiling point of the brake fluid, whereby the danger of vapor lock formation is present. Therefore it should be noted that brake fluid is always stored in sealed vessels. Brake fluid that has been stored unsealed can absorb so much moisture in a few hours that it is rendered unusable.

Because the brake fluid also absorbs moisture through the vent bore on the expansion reservoir, the wheel brake cylinder and the brake hoses, the brake fluid has to be changed for safety reasons at regular intervals, best done in the spring. When performing this change, make sure that the old fluid is also drained off the clutch system. Generally, it is vital for the brake/clutch system to be completely drained before being filled with new fluid!

For the above-mentioned reasons, used brake fluid must not be used again.

The brake fluid is amber in color and thus can be easily confused with mineral products.

Therefore, brake fluids should always only be taken from original containers and stored separately from other mineral oils and fluids.

When performing maintenance operations and repairs on brake parts, make sure that fuel, mineral oil, grease or suchlike do not enter the brake system. Hydrocarbon-based materials will lead to swelling of the elastomers in the brake and clutch system and - even in low concentrations - will suffice to cause total failure of the systems.

Only new brake fluid may be used as a rinsing and cleaning agent for the cylinders, lines and the expansion reservoir of the hydraulic brake system.

Experience shows that before handling brake fluid, the hands must be cleaned and any oil and grease removed.

Brake fluid acts aggressively towards paint and color. In the event of any brake fluid spills or splashes, it must be rinsed away immediately using copious amounts of water (do not rub it away).

Brake fluid disposal 

When disposing of brake fluid, the relevant national specifications must be observed. It is advisable to try to have the brake fluid disposed of as economic good; this is contingent on

• Strict separation of used brake fluid from other materials;
• Presence of a disposal channel, which justifies its classification as an economic good, i.e. a proper alternate usage must be assured.

If this procedure is not possible, used brake fluid is to be disposed of together with any, e.g. paint residue, solvents and suchlike. Any adding of used oil must be avoided, as it will result in difficulties, if the used oil is to be recycled; in several countries this is prohibited by the legislators.