553 Brake Systems Technician Handbook Brake Fluid Brake fluid must: • Have a high boiling point to prevent hydraulic fade. • Have a low freezing point so that it does not freeze even in very low temperatures. • Lubricate moving parts, such as the piston seals. Most brake fluids are based on Alkyl Polyglycol Ether Esters, or “ Polyglycol. ” Poly-glycol is: • Clear to amber in color. • A solvent that will dissolve paint on contact. Flush paint with water to remove spilled brake fluid Have a low freezing point so that it does not freeze even in very low temperatures. • Hygroscopic, and attracts water through hoses, past seals, and through the vent in the reservoir cap.
Moisture reduces the brake fluid’s boiling point corrodes metal parts, so brake fluid containers should remain tightly closed to prevent moisture from contaminating the fluid. IMPORTANT While all brake fluids must conform to certain government standards for boiling point, not all brake fluids meet Toyota ’ s standards for lubrication and corrosion resistance. Toyota recommends the EXCLUSIVE use of Toyota brand DOT 3 brake fluid in all its products. Using brake fluid that does not meet Toyota ’ s standards may introduce moisture, debris, petroleum based fluids or other contaminants into the brake system. This can damage brake system components and decrease braking efficiency.
Do not mix brake fluid with any other fluid, including other brake fluids from partially filled bottles. NOTE Some brake fluids are silicone based. Silicone-based brake fluids are: • Purple in color and typically used in show cars or other specific application. • Not corrosive to paint, but have a higher affinity for air than polyglycol. • NOT compatible with polyglycol-based brake fluids.” 8 Technical Training