Problem: Low, spongy brake pedal
Cause: Air trapped in hydraulic system
Solution: RFI is a patented process from Phoenix Systems. The Phoenix Injector has been designed to perform RFI as well as pressure and vacuum bleeding. To perform RFI follow the steps below:
1. to perform RFI bleeding, first drain and clean the master cylinder reservoir. If necessary fill the before draining so an accurate measure of fluid can be taken. Note the amount of fluid removed. This will be necessary to avoid overfilling the master cylinder during the RFI bleeding process. In order to give the air an easy path out of the master cylinder raise the rear of the vehicle to allow the master cylinder to sit higher at the primary end (firewall) then at the secondary end. This will allow the air to exit the vent ports.
2. Remember caution is to be used when raising the vehicle to avoid an unsafe condition or vehicle damage. If the master cylinder cannot be positioned in this manner, get it to at least a point where the body is level. If this is not practical then remove the master cylinder from the vacuum booster and gently flex the brake lines to position the secondary end of the master cylinder (bumper end) lower than the primary side (firewall end). This will position the vent ports at the highest point.
3. Configure the Phoenix Injector for RFI bleeding as per the instruction manual. Follow instructions for priming the injector and lines. Once the master cylinder has been positioned then begin the bleeding process at the first wheel in the bleeding sequence. Connect the injection side of the tool to the bleeder and the vacuum side to the fluid supply container making sure it is full.
4. With the tool connected, open the bleeder screw and the slowly stroke the handle. Continue this at the wheel giving at least three to four strokes.
5. Once complete, remove the adapter from the bleeder and let the wheel cylinder or caliper burp or gravity bleed. Close the bleeder.
6. Repeat this process at each of the wheels remembering to watch the amount of fluid being used. It may be necessary to drain the reservoir during the process to avoid overfilling it. At the end of each wheel bleed remember to allow the caliper or wheel cylinder to gravity bleed.
7. Once complete check and adjust the master cylinder fluid level and test the pedal. If firm, test drive.
CAUTION: Never drive a vehicle with an unsafe pedal.
More Info: All bleed procedures published in service manuals are based on conventional bleeding techniques. Whether they work or not and how quick will depend on where the air is. In addition to these there is another relatively new technique available. It is called RFI, which stands for Reverse Fluid Injection.
RFI Exceptions: There is only one case where I am aware of where RFI will not work. It involves a unique style master cylinder. Master cylinders are supposed to have vent ports right? Well that’s what I thought too until about 5 years ago. TEVES makes a master cylinder that does not use vent ports. It uses valves in the center of each piston to control venting (See Figure 76.2). RFI will not work on this style of master cylinder because the air forced back to the master cylinder will be trapped above the check valves. These master cylinders seem to be used only on vehicles equipped with the TEVES IV ABS system. The reason for the elimination of the vent ports was to prevent damage to the cup seals during ABS operation. These master cylinders can be identified by looking for the large tube the connects the reservoir to the ABS modulator. The good news if that most of the time these systems do not prove too difficult to bleed.