Coolant is depleted of buffering ingredients and becomes extremely corrosive, literally eating holes in cooling system components. By-products of corrosion damage, as well as rust and scale, clog the passageways that conduct the water through the radiator and choke off the flow. This may result in an overheated engine that may be damaged beyond repair.
After 30,000 miles, transmission fluid begins to show its age as it turns brown in color and oxidizes due to the combination of time and heat. Deposits begin to form around the transmission's many moving parts, resulting in valves that stick and gears that slip or are sluggish and chatter as they shift.
The power steering pump produces high pressure between 800--2000 pounds, with high heat. This leads to fluid breakdown and failure. Symptoms include groaning and whining noises, erratic steering and pump leaks.
Brake fluid becomes oxidized and contaminated over time and use. Heat and moisture cause corrosion on parts and brake fluid failure. This causes a spongy brake pedal and shows up in discolored brake fluid.