Pressure bleeding is done with a device that forces fluid into the reservoir and as a result air is pushed through the system and released at the bleeders as with standard procedures.
Vacuum bleeding is done with a pump attached to the bleeders. Fluid is drawn into a container through a clear plastic hose. When no bubbles are seen in the fluid the system is bled.
When Should You Change Your Brake Fluid?
As we’ve pointed out brake fluid will absorb moisture from the air, so use is less of a factor than you might think. Interestingly, most domestic automobile manufacturers don’t provide recommended intervals for changing brake fluid, however most European and Japanese companies recommend changing fluid anywhere from 24-36 months.
Considering the fact that as little as 1 percent water can reduce the boiling point of brake fluid any contamination is cause for concern. Given the minor investment involved, and the possible benefits in an emergency situation, changing brake fluid regularly should be part of your street rod’s maintenance program.