Replacing Brake Fluid? Why?

October 5th, 2015
Brake Repair in St Louis, MOIn some cases, your technician might need to replace brake fluid when servicing your car’s brakes. While brake fluid is usually good for years at a time, there are a couple of reasons why that might be the case. 
 
Anytime that the brake system is opened up, such as when a caliper or wheel cylinder is replaced, air is introduced into the brake lines. In these instances, it’s necessary to purge the air from the lines; bubbles of air in the hydraulic fluid of the lines will compromise braking performance. This process is known as “bleeding the brakes.” 
 
Brake bleeding is done one wheel at a time, forcing fluid out and watching closely for bubbles. By the time all four wheels are done, it’s not unusual to add an entire quart of brake fluid back into the system again, which will effectively purge all the old fluid out and replace it. 
 
It’s also important to remember that brake fluid is hygroscopic, meaning it attracts and retains water. That water can raise the boiling point of brake fluid, hurting brake performance in repeated use such as in hilly terrain. It can also lead to corrosion and pitting of steel parts in the system, which can contaminate brake fluid and even lead to brake repair and replacement of certain crucial parts. 
 
Some manufacturers now recommend a brake fluid flush at a two-to-five-year interval. It’s important to know that not all brake fluids are the same – while older fluids used a glycol base, newer high-performance brake fluid is silicone-based. The fluid are not interchangeable; check your owner’s manual for manufacturer’s recommendations. 
 
You can easily check your brake fluid’s level and condition by unscrewing the tops of the master cylinder (as pictured), located on the engine bay’s firewall. The fluid should be clear and slippery (don’t get it on painted surfaces, it’s an effective paint remover). If it’s dark and/or gritty, you might be in need of a brake fluid flush. If you’ve got any doubts, give us a call or schedule an appointment at Master Auto Repair in St. Louis, MO and let us have a look! 
  Posted in: Auto Repair 101