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Wednesday, February 20 , 2019, 6:03 pm | Mostly Cloudy 51º


Brake Fluid Tips from Superior Brake & Alignment

Moisture is the most common contaminant, and its effects can be costly

Santa Barbara has trusted Superior Brake & Alignment’s high-quality brake service for nearly 30 years.

Along with excellent service, we would like to educate our customers on a simple, yet very important component of the brake system. Please take a moment to read about it.

Brake fluid is the most important fluid in your car. Your brake fluid is more important than gasoline, for reasons that should be obvious.

It has the responsibility of working flawlessly every time it is needed for years and years, miles and miles. Not much attention is given to it until there is a problem. Yet it is probably the most neglected fluid in your vehicle. Sure, we check the level now and then, but who would ever think of changing it? Yet brake fluid, just like every other fluid in your vehicle, breaks down and becomes contaminated, and eventually it even becomes harmful to the components it serves, such as the steel and aluminum brake cylinders.

The most common contaminant is moisture. Because DOT 3 and DOT 4 brake fluid is hygroscopic (yes, hygroscopic — not hydroscopic, as it is commonly called) it attracts and absorbs moisture. Moisture was more of a problem back in the early days of the automobile, all the way up to the early 1960s master cylinders vented to the atmosphere, and humid air contaminated the fluid. Even in modern cars and trucks, heat and cold, expansion and contraction, master cylinder caps and seals can let in moisture.

The moisture causes two potential system failures. One is that brake fluid has a very high boiling point — 401 degrees Fahrenheit for DOT 3, 446 degrees Fahrenheit for DOT 4. Studies have shown that even a modern system can absorb 2 percent of its volume in moisture in 12 months. Just 3 percent moisture by volume reduces DOT 3’s boiling point 25 percent. Dot 4 fluid has a higher dry boiling point to begin with, but suffers an even lower drop in boiling point than DOT 3 with the same amount of contamination.

The problem with all of this is that with heavy braking or emergency use, the fluid can boil unexpectedly, causing vaporization and pedal failure. With no pedal, it’s pretty hard to stop a vehicle!

The other problem the moisture causes is metal deterioration. Brake fluid by itself is a rust inhibitor, but when even a small amount of moisture is absorbed, it turns caustic and corrodes the master cylinder, wheel cylinders, calipers and every other metal part of the system. This is especially true with vehicles that sit for long periods of time, such as the family classic car.

The effects of moisture in the fluid can be costly. We recommend changing the brake fluid every couple of years. Think of it as cheap insurance!

Superior Brake & Alignment is located at 822 N. Milpas St. in Santa Barbara. The phone number is 805.962.1417.

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