The opinions expressed herein do not necessarily reflect those of the National Street Rod Association and/or StreetScene Magazine. Out of Sight, Out of Mind
W hen was the last time you changed your brake fluid?” Most people know that routine car care involves checking the brakes and squeaky ones usually get immedi- ate attention. But if your car’s brakes seem sluggish and it’s taking longer to stop than is normally nec- essary, a simple brake fluid change could restore your brake’s good, hard pedal. Brake fluid is an “out- of-sight, out-of-mind” component of the brake system, so other than checking the fluid levels in the reservoir, we don’t think of it until something goes wrong. Our brake fluid is working hard every day to keep us safe on the road and over time it can experience boiling tem- peratures, risk of depletion, or it can become contaminated, pre- venting proper brake function.
Brake fluid is hygroscopic, meaning it’s notorious for absorbing water. Although brake fluid absorbs water like a sponge, you don’t want your pedal to feel like a sponge when you jam on the brakes. A vehicle using fresh brake fluid should deliv- er a solid brake-pedal feel, like you’re pressing down on a brick. Think of the last time you drove a new car. The brakes likely inspired confidence and felt rock-solid. That’s because the entire system was brand new and moisture had yet to infiltrate the fluid. Fresh brake fluid has a boiling point that is a higher temperature than would be produced while braking. However, water has a much lower boiling point and can boil from the temperatures pro- duced during braking. Moisture which has been absorbed by the
brake fluid can boil, releasing gas. With this gas in your braking sys- tem, pressing the brake will simply compress the gas, instead of push- ing the brake fluid to your wheel cylinders or calipers. There are any number of brake-fluid testing ‘strips’ or devices on the market solely to test for moisture in the fluid. But here’s the kicker, even if you do everything in your power to prevent moisture absorption, brake fluid will absorb moisture in a variety of ways, whether through the packaging process, while pour- ing it into the reservoir or from air in the brake fluid lines. If the level of fluid in the reservoir is not kept topped off, air filling the vacancy in the reservoir contains moisture that can lead to corrosion throughout the brake’s hydraulic system. There is no set time to change the brake fluid in your vehicle. The timing varies by type of car, the driving conditions you typical- ly encounter, and the manufactur- er’s recommendations. But a good rule of thumb is to check it during regular oil changes and expect to change it every four to five years. Signs that you should get your brake fluid checked immediately include fluid that has a burnt odor, is not clear or transparent, or is at a lower level than it’s sup- posed to be. There are many types of brake fluids with different rat- ings and specifications, and they shouldn’t be mixed. As a rule of thumb DOT 3 & 4 will fill most needs but when you step up to high performance silicone DOT 5 the products can’t be mixed. I hope the next time you do routine maintenance on your vehi- cle you will remember to check your brake fluid and keep in mind, over time accumulated moisture could lead to a spongy situation. Carol Barnhill Arkansas State Inspector
104 SEPTEMBER 2025
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