Substandard or Contaminated Brake Fluid

Improper brake fluid, mineral oil (i.e., power steering fluid and transmission fluid) or water in the fluid may cause the fluid to boil, or the rubber components in the brake hydraulic system to deteriorate. If the master cylinder cap diaphragm is swollen, then rubber parts have deteriorated. This deterioration may also be evidenced by swollen wheel cylinder boots and caliper boots.