Vacuum bleeding involves pulling air bubbles through the system and out the calipers. We do this by stepping on and off the brakes or by using a machine that applies pressure and fluid via an adapter at the master cylinder.
Finally, there is bench bleeding, which involves a bleeding component not installed on the car, like a new master cylinder. Different tools can bleed vehicles in different ways.
You can do any of these with a vacuum/pressure pump (such as a Matco Tools No. MVP 5000) as long as you have the right adapters. However, some companies make more specialized tools for this task.
Some tools “reverse bleed” the vehicle. One such example of this is Phoenix Systems’ MaxPro Brake Bleeder. Instead of pumping the air out through the lines out of the brake bleeder, this tool pushes the air up and out the master cylinder.
The tool is a pump that directly handles the brake fluid, not a vacuum pump that forces the air out the top of the master cylinder reservoir. In just a few minutes, the pedal is firm. This will work on any hydraulic system. It allows pressure, vacuum and reverse bleeding.
With the MaxPro, in order to bleed a master cylinder, a universal port adapter screws onto the front of the bleeder in place of the outlet hose. Push the port adapter into the ports of the master cylinder inlet, and squeeze the handle to bleed air bubbles out.
You can reverse bleed the piece by going in the master cylinder outlets. Pressure bleeding is similar but done on the vehicle. It forces fluid in at the master cylinder and out through the caliper bleed screws.
When the pedal refuses to lose its sponginess, the best technique is to use a combination of bleeding techniques, such as pressure and reverse bleeding or reverse and vacuum bleeding.
An example of a brake fluid exchange tool that vacuum bleeds is RTI’s BFX-2 Brake Fluid Exchange System. This tool works by pushing fluid through the master cylinder, while simultaneously applying vacuum to the appropriate brake bleed screw. Fluid is moved from the master cylinder through the lines and out of the calipers, taking any air out with it. In order to pressurize fluid through the master cylinder without creating a mess, the tool comes with a variety of adapters designed to fit the master cylinders of many makes and models.
Other pressure bleeding tools such as the BrakeMate Brake Flush Machine from Flo-Dynamics address the issue of bleeding sequence. The BrakeMate has a “select sequence” feature that allows the tech to select the desired sequence for flushing as specified by the manufacturer.
The BrakeMate Jr. eliminates suction lines and includes a catch bottle giving the tech the freedom to follow the bleeding sequence. It also has an adjustable regulator to increase supply pressure which is required to bleed hybrids and some high end sport cars.
Brakes may be a profitable part of this business and not too difficult to diagnose. However, intermittent problems and spongy pedals can turn customers off, as brakes are one of the most important items on a vehicle. To maintain a good reputation and have no comebacks, the right tools are necessary.