- Car Care & Maintenance
Brake fluid services help you stop sooner
Brake fluid = Sponge
Brake fluid services have suddenly become popular over the last few years. Almost all import vehicles have recommended service intervals for brake fluid exchanges. So why has this seemingly simple fluid suddenly become so important? Fact is, it's always been important, it just hadn't been emphasized. The development of proper tools and techniques makes this possible.
Some simple facts. Brake fluid is hygroscopic, which means that it absorbs water. Brake fluid is actually manufactured under a blanket of nitrogen to keep any moisture in the air out. All brake fluid comes in sealed bottles. Once the seal is broken, it's best to use the fluid and discard the remaining. An unsealed bottle will absorb moisture and lose it benefits.
Stopping now or later
Here's how stopping properly and your brake fluid relate. When the brake lines are properly filled with the correct fluid, the force of your foot pressing on the brake pedal is transferred directly to the brake friction components. Now consider that when a vehicle is stopping from highway speeds, those friction components can get pretty hot. Put your hands together and rub as fast as you can. Now imagine the full weight of your vehicle being stopped at high speed between your hands. That's a lot of friction which means a lot of heat. In a study sponsored by the Washington State Department of Transportation, brake pad temperatures can reach 800 degrees in a 60 mph stop at a low grade incline. The brake line containing the fluid is routed within a inch of this sudden heat blast. With a water concentration of 3.7 %, dot 4 brake fluid will boil at 311 degrees, and dot 5 will boil at 356 degrees.
When brake fluid boils in the lines, vapor forms. Vapor compresses under pressure. This causes the brake pedal to go from feeling solid, to feeling soft and mushy. This can cause an increase in stopping distance of up to 30 feet or more. That could be all the difference between a safe stop or a crash. I have heard that many state police departments now do annual brake fluid changes.
The exchange process
With the estimated rate of water absorption being around 2% a year, most manufacturers suggest fluid exchanges every 2 years. The process is simple and usually takes about an hour.
The technician installs a special cap onto the brake fluid reservoir. A line from the fresh brake fluid container is attached. A line with a container is then attached to one of the brake caliper bleeder screws (pictured). The system is then pressurized using shop air. This process is repeated at each wheel. At our facility, the entire contents of a brake fluid drum is used in the process. Using the system we use helps to insure that nearly no air can enter into the system and contaminate the new fluid. This is very important because it's kind of pointless to have the system wide open exposed to the open air.
The average cost of this service is right around $150.00 depending on where you go. Also, if the maintenance is performed early in the life of the vehicle, most facilities will warranty some brake system components. This is good because an ABS hydraulic control module can be about $1000.00 to replace.