Automotive Maintenance Change the Brake Fliud
Passenger cars and trucks use DOT 3 and DOT 4 brake fluid, they are glycol based and absorb moisture over time. Moisture contamination causes the fluid boiling point to drop which could lead to the fluid boiling to soon and cause brake fade during hard use.
Moisture contamination also contributes to internal corrosion in the calipers, wheel cylinders, and metal brake lines. The reason for replacing brake fluid is to get rid on contaminated fluid and restore the fluid heat and corrosion resistance. Moisture seeps in through microscopic pores in rubber seals and hoses. It also enters every time someone opens the master cylinder reservoir to check the fluid level. Most fluid reservoirs are transparent so the level inside them can be checked without having to remove the cap.Brake fluid is so hygroscopic (attracts water) that leaving the lid off a can of fresh brake fluid can ruin overnight. It will absorb so much moisture from the air that it becomes too badly contaminated to be used.
How often should you replace the brake fluid in your car? By the time a new car is only 12 months old its brake fluid contains about 2% water. After 18 months, the water content is approaching 3%, which is enough to lower the boiling temperature by 25%. After several years of service, it is not unusual to find brake fluid containing seven to eight percent water. For this reason, many experts recommend replacing the fluid as preventative maintenance service every two years or 24,000 miles. At the very least it should be replaced when brakes are relined, usually the master cylinder is checked for proper level if the fluid is dark (color of iced tea or darker) it should be replaced, the dark color means that it has been boiled due to moisture contamination and is starting to corrode metal lines and break down rubber hoses.Brake fluid is toxic so the best and most "green" way to replace your fluid is in a repair shop. A complete fluid flush can run from $80-$150 depending on region and labor rates, it seems like a simple operation however it pretty tedious and several bottles of fluid will be needed.
