The Rolls-Royce in the photo above is a prize-winner, as the one in this story. Just not the night it failed to proceed. Imagine the scene . . . .
- · The wheel bearing could have failed and overheated the area
- · The brake could have dragged and overheated the rotor and hub
- · The overheated parts would smoke
- · The hot rotor would vibrate
- · If the rotor got hot enough, it would boil the brake fluid, which would make the pedal go to the floor, and light the lamp
- · If the hub got hot enough, grease would melt out of the bearing and perhaps remain on the brake disc.
- · There would be no loss of fluid and it would look fine when cool.
- · The caliper pistons could be frozen
- · Pads could be rusted in the caliper
- · The conventional master cylinder to the rear wheels could have stuck
- · One of the distribution valves might have leaked
- · The brake hoses might have swelled, preventing release of fluid
Above - the rear hub bearings, Note the outer is greasy, while the inner bearing is about dry. Neither has failed, but without attention, the inner bearing would have burnt up soon.
Above - a failed caliper piston. The rust line is where the piston enters the seal area.
Above - the other side was worse
Above - a closeup of the corresponding caliper bore shows rust damage and roughening. This surface must be perfectly smooth and even. If it's too rusty to clean up, we split the caliper, bore it oversize, and press in a sleeve.
With these observations, we can paint a picture of how and why this system failed.
- The small pistons in the right rear caliper corroded and became tight, which made the brakes drag slightly.
- When the car got up to speed the drag got the brakes hotter and hotter, which eventually warped the rotor and caused the shake.
- The hot rotor melted the grease causing some to run out onto the rotor as the car cooled. That was what we saw, and it caused the smoke the driver saw.
- The hot brakes boiled the fluid, which caused the pedal to go to the floor, and light the lamp
- The leaking distribution valves were not part of this failure, but they leak excessively and should be changed before they cause a bigger problem
Above - the other side's caliper pistons were not dragging as much, but they all show rust breaking through, which is the seed of failure whether now, next year, or two years hence. Best fix it before it leaves the car stranded.
Bear in mind that the damage you see in these photos is on a well-maintained car. This is not damage from neglect. The brake fluid is clean and clear, but nothing stops rust from outside, especially in a car that lives near the ocean, as this car has for 30+ years.
Above - For comparison, here is what fluid looks like in a system that was neglected. Needless to say, that car has much bigger problems.