Part Focus: Brake Fluid / Brands: MPM, Duckhams
World class oil and lubricants supplier MPM offers their knowledge on the importance of changing brake fluid.
MPM often receives maintenance questions about the use and product expiry of brake fluid in vehicles. It is vital that the workshop and end user are aware that there are stringent maintenance regimes that should be adhered to regarding maintaining the brake fluid. Modern braking systems and fluids are very complex and require as per manufacturer specification, higher levels of monitoring and change outs to meet the requirements of modern fleet. In this article, you will find a brief explanation of what happens to the fluid over time, but also the importance of using the correct fluid at service. In addition,we have also included important tips for use in the workshop. Summary:
Replace the brake fluid at least every two years. This can save lives.
Never mix brake fluids of different groups with each other.
For cars built from 2007 a DOT4+LV brake fluid is often prescribed - this is not always shown on the brake fluid reservoir.
DOT4+LV may also be used where DOT4 is prescribed. Our advice is therefore to use DOT4+LV, also where DOT 4 is prescribed.
Tips for the Workshop
Preferably use brake fluid from a sealed package
Choose the packaging form and size In such a way that no residue can be stored
Brake fluid can also affect some types of paint. If the brake fluid spills, rinse it thoroughly with water, do not rub away
Visit www.mpmoil.co.uk - you can quickly and easily see, based on the vehicle license plate, which brake fluid is prescribed for the specific.
Replace the brake fluid every 2 years.
Brake fluid must be renewed every two years, in addition to the mileage-related maintenance. We are regularly asked if this is absolutely necessary, and the answer is, yes. This is for your own safety and the safety of others. The next question that arises is, ‘why’. The most commonly used brake fluids (DOT 3, DOT 4 and DOT 5.1) are hygroscopic, i.e. they attract water. This property means that the boiling point drops drastically (3% water can already lower the boiling point to more than TOT). When brakes are heavily loaded (for example during intensive city traffic; driving with extra weight or in mountainous terrain) water vapour can then develop. Water vapour is compressible and therefore your brakes will not function as they were designed to do. In this type of fade, the brake pedal feels “spongy”. If temperatures drop below freezing another issue with the build-up of excessive water can mean that brake lines are blocked and cause brake failure. In addition to the danger of the brakes no longer working properly, the presence of water can also mean corrosion, especially in the very expensive parts of the ABS and stability control system.
How can water enter the brake fluid?
There are various ways as to how water can contaminate brake fluid. For example:
In the packaging - after opening and / or breathing from the plastic container. Storage in tin cans Is therefore preferable.
By entering at the main / brake cylinders.
By entering at the pipe / hose connections.
When refilling (water vapour in the air). Unfortunately, these causes are difficult to prevent, which is why it is important to change the brake fluid at least every two years.
Three groups of brake fluids:
We can distinguish three main groups of brake fluids, namely:
Brake fluid based on polyglycol ethers: DOT 3, DOT 4, DOT 4+ LV, DOT 5.1 - Clear or amber (not artificially coloured)/
Brake fluid based on silicone fluids:
DOT 5 - Purple.
Brake fluids on mineral oil basis:
Mostly Green
Until 1976, brake fluids based on polyglycol ethers were coloured blue. The above three types of brake fluids must NEVER be mixed with each other!
Brake fluids based on polyglycol ethers are in principle interchangeable. However, it may be that a DOT 3 is specifically prescribed. The reason for this Is usually because the used sealing materials are less resistant to the DOT 4 brake fluid.
DOT 4 or D0T4+LV?
For most vehicles which have been produced from 2007, a DOT 4+ LV is prescribed as mandatory by the manufacturer. Our experience has demonstrated that not everyone is aware of this. This brake fluid has a so-called Mow viscosity’. This low viscosity is essential to ensure the proper functioning of the braking system at cold temperatures. This brake fluid is also specially developed for braking systems that include ABS, ESP and ASR. To enable these systems to respond quickly, a DOT 4+ LV fluid Is required. The DOT4+ LValso has a high ‘wet boiling point’ which will reduce the chance of vapour bubbles and liquid boiling. More about this later. The difference in the specification can be found in the Class 6 addition:
DOT 4 = FMVSS116 ISO 4925
D0T4+LV = FMVSS116 ISO 4925 Class 6
Note: DOT 4 is often inscribed on the cap of the refill reservoir of the master cylinder, but in many cases the DOT 4+ LV should be used. Often this is not on the reservoir and therefore reference should be made to the operating manual of the vehicle.
Difference between dry and wet boiling point.
The DOT standard Indicates the boiling point of the brake fluid. A distinction is made between:
Dry boiling point where the brake fluid contains 0% water
Wet boiling point with a maximum saturation of over 3% water
The table below demonstrates the different DOT designations which are differentiated according to the international standard requirements.
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