Shop Talk: Brake fluid most important

Brake fluid is perhaps the most important fluid of all in a vehicle, because without it, we couldn’t stop!

It’s also one of the most neglected vehicle fluids, ranking right up there with anti-freeze. Master mechanics recommend that brake fluid be changed when it becomes contaminated by moisture, which lowers its boiling point to a dangerous level and thus decreases brake efficiency.

To be safe, we recommend changing brake fluid at least every three years. If you travel more miles than the average driver or use your vehicle mostly in stop-and-go traffic, changing fluid every two years is recommended. Every time you use your brakes, the fluid absorbs just a wee bit of moisture. After a year, the brake fluid in the average vehicle may contain as much as 2 percent water. After several years of service, it’s not unusual to find brake fluid that contains as much as 8 percent water.

This effectively lowers the fluid’s boiling point, increasing the danger of a brake failure because vapor pockets form if the fluid gets too hot. Vapor thus replaces fluid in actuating the brake lining against a drum or disc, so that when brakes are applied, the pedal may go “soft” or, in a worst-case scenario, go all the way to the floor.

The National Highway Traffic Safety Administration found that brake fluid in 20 percent of 1,720 vehicles tested recently contained 5 percent or more water. This finding should convince motorists to have their mechanic check the brake fluid on a regular basis.