An important part of the brake system is the brake fluid. The brake fluid is a vital topic because a lot of brake system maintenance don't include the brake fluid test to know when it should be changed.
Most car's and medium sized trucks that are more than five years old haven't had a brake fluid change for those years of service.
WHY CHANGE THE BRAKE FLUID.
A lot of car owners /drivers don't change the brake fluid because they don't know why.
Considering the fact that a brake fluid that has been in service for more than 3 years has been contaminated by moisture, and this will affect the brake fluid quality as the boiling point would have reduced to a dangerous level. For a lot of people who don't know why the brake fluid should be changed, that's a reason.
Part of the reasons why the brake fluid absorbs moisture is due to its hygroscopic nature. That's why unnecessary opening of the brake fluid reservoir filler cap should be avoided.
The brake fluid is stored in a white translucent plastic container with a minimum and maximum level mark so you can know the fluid level without opening the container.
CHECK THE FLUID LEVEL.
It is important to check the brake fluid level frequently . The level will gradually reduce as the brake pads wears out. But when you notice an unusual sudden drop in the fluid level, it means there is a leakage somewhere in th brake system, it may be the pipes/or hoses, through the worn out seals of. The brake master or pistons. The fluid level should be maintained between the MIN and MAX mark on the brake fluid reservoir, it should not be lower than the MIN mark and shouldn't exceed the MAX mark. Ensure that you use the specified type of fluid. It is usually written on the brake fluid filler cap, if your filler cap writes DOT 3, you should use DOT 3 brake fluid, and if it writes DOT 4 you should use DOT 4 brake fluid.
WHEN SHOULD THE BRAKE FLUID BE CHANGED.
Experts have recommended that the brake fluid be changed every year or two. Based on the fact that some glycol-based brake fluid starts to absorb moisture once it is put into the brake system. The fluid attracts moisture through the microscopic pores on rubber hoses, seals and exposures to the air. The process is obviously high during wet climates, when the humidity is usually high.
After a year the brake fluid in an average vehicle may contain as much about two percent of water, and about 18 months the water level may increase to 3 percent, and after several years of service the level of contamination would have increased the percent of water.
As the level of the water increases in the brake fluid, it causes a sharp drop in the boiling point of the brake fluid.
A typical DOT 3 brake fluid must have a dry(no water) boiling point of at least 401 degree F, and a wet(moisture saturated) boiling temperature of not less than 284 degree F. Most new DOT 3 fluids exceed these marks and may have a dry boiling point that ranges from 460 degrees up to about 500 degrees.
On the other hand, a DOT 4 fluid which does not absorbs moisture as the DOT 3 fluid, it absorbs moisture more slowly. The DOT 4 has a minimum dry boiling temperature of 446 degree F and wet boiling temperature of 311 degree F. A lower amount of contamination can cause a sharper drop in the boiling temperature compared to the DOT 3. 3 percent of moisture can reduce the boiling temperature by 50%.
A lot of the recent front wheel drive brake system with semi-metallic lining gets significantly hotter than the rear-wheel drive counterparts. High brake temperature require brake fluid that can take the heat, but has the brake fluid in most vehicles today have already been contaminated by moisture, such contaminated fluids will not be able to take the high level of heat produced.
THE DANGER OF OLD BRAKE FLUID.
An old brake fluid more than a year is likely to have been contaminated with some percentage of moisture. A water contaminated fluid will increase the danger of brake failure. When the fluid gets hot, water vapours form due to the presence of moisture in the fluid. The Vapour formed displaces fluid and is compressible. When the brake is applied, the pedal may go down to the floor without applying the brakes.
Another problem of a moisturised brake fluid is promoting corrosion and pitting in caliper pistons and bores, wheel cylinders, master cylinders, steel brake lines and ABS modulators.
WHEN TO CHANGE THE BRAKE FLUID.
The best recommendation is in your owners manual, or maintenance manual. That is where manufacturers specify when the brake fluid should be changed, it may be recommended in Miles or times.
The number of major car makers and their specifications on brake fluid change.
Acura: 36 months
Audi: 24 months
BMW: 24 months, or when indicated by Service Inspection Indicator
Honda: 36 months
Jaguar: 24 months all models except 2009 XF (36 months)
Land Rover: 36 months
Lexus: 36 months or 30,000 miles, which ever comes first
Mercedes-Benz: 24 months
MINI 24 months
Saab: 48 months (all models except 9-7X)
Smart: 24 months or 20,000 miles, which ever comes first
Subaru: 30 months or 30,000 miles (normal service) or 15 months/15,000 miles (severe service)
Suzuki: 24 months or 30,000 miles, which ever comes first (Forenza & Reno), 60 months or 60,000 miles (Grand Vitara and SX4)
Volkswagen: 24 months (New Beetle, City Gold, City Jetta), 36 months (all other models except Routan)
Volvo: 24 months or 37,000 miles (Normal), or 12 months (severe service)
If motorists would only follow this simple advice to change their brake fluid periodically, they could greatly reduce the risks associated with moisture-contaminated brake fluid. You can extend the life of your brake system and likely save yourself a lot of money in the long run on brake repairs, especially if your vehicle is equipped with ABS (because ABS modulators are very expensive to replace!).
Read more about brake system maintenance
Read more about brake system maintenance
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