That’s our dot five is silicone based. All the other ones are glycol based. So you go to take an ASE exam, just know dot five is silicone, the rest are glycol, the higher the number, the higher the boiling point, and you’ll be good to go.
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This document discusses brake fluid types and brake valves.
Brake Fluid:
- DOT 3, DOT 4, DOT 5, and DOT 5.1 exist.
- Higher DOT numbers generally indicate higher boiling points.
- Always use the manufacturer’s specified brake fluid. DOT 4 can supersede DOT 3.
- DOT 5 is silicone-based; all others (DOT 3, 4, 5.1) are glycol-based. Do not interchange DOT 5 with other types. DOT 5 is typically found in military vehicles and some motorcycles.
- Brake fluid is hygroscopic (absorbs water), which lowers its boiling point and can cause brake fade. Regularly check and maintain brake fluid.
- Metering Valve (front brake lines): Holds off front brakes until rear brakes apply. A faulty metering valve can cause rear wheels to lock up under light braking (nose-diving).
- Proportioning Valve (rear brake lines): Reduces brake force to the rears during hard braking to prevent rear wheel lock-up. Height-sensing proportioning valves, if an axle is hung on a lift, may prevent fluid from bleeding.
- Pressure Differential Switch: Turns on the “red brake warning light” (ribble light) if one side of the dual-channel system loses pressure, indicating a leak.
