Here, Sims is bleeding the brakes with the RFI method. He's injecting clean fluid into the
To do this, attach the injector to the caliper bleed screw so that it is injecting fresh brake fluid into the caliper. Begin, as you always should, with the caliper farthest from the master cylinder and work your way so that you finish at the caliper closest to the master cylinder (normally the left front). Also, lightly squeeze the Injector handle before attaching the end of the line to the bleeder screw to make sure there is no air in the Injector or attached hose. Phoenix Systems says that only three to 10 full pumps are needed at each caliper to do the job. Then, after removing the Injector, allow a small amount of fluid to drip from the hose connected to the bleeder valve in order to "burp" any trapped air from the brake system and close the bleeder valve.
Overall, the Phoenix Injector system worked very well. There are a lot of components involved, and hooking everything up can seem a bit complex at first. But once you get the hang of it, you will find that it will help you maintain a firm pedal and good braking performance every time you go to the racetrack.
This is an in-line filter to help you keep the Injector clean when pulling old fluid out o
Choose The Right Fluid
You may hear about some special types of brake fluid on the market that aren't hydroscopic and won't degrade by absorbing water. And it's true, this fluid is silicone based and won't draw moisture. At first, that may seem like the perfect answer to all your brake system problems-they also have a DOT 5 rating which means an extremely high boiling point-but resist the urge to put either in your race car.
According to information provided by Afco Racing Products, Silicone-based Polymer brake fluids are sold for street applications and are popular among the show-car set because they don't eat paint like traditional brake fluids. But they have one particular drawback, and it's a big one.
Silicone-based fluids are highly compressible. So even with fresh fluid in a perfectly spec'ed out brake system, you won't be able to get rid of the feeling of a spongy pedal. And it only gets worse as the temperature of the fluid rises. So even if it never hits its boiling point, silicone-based fluid is going to provide poor braking performance and rob you of any feel from the pedal. Don't be fooled by the DOT 5 rating, which many racers equate with performance. Silicone-based brake fluid is not a racing quality product.
Here, Sims uses the vacuum method to pull oil fluid from the caliper and dump it into the
A Good Reason To Flush Your Brake Fluid Regularly
A long with the valuable tip to stay away from Silicone-based brake fluids, AFCO also passed along this chart listing the boiling temps for brake fluids with different DOT (Department Of Transportation) ratings.
One important thing to note is that the dry boiling point for many of these fluids can actually be higher than the rating. For example, AFCO says that its 570 Degree brake fluid is rated DOT 3 but has a dry boiling point of 570 degrees F. (Wonder where they got the name?) But even though its boiling point is 169 degrees higher than DOT standards, it still gets a category three rating because of its wet boiling temp. This is true for any poly glycol-based fluid (non-silicone); the dry boiling point is going to be significantly higher than wet. And since race cars produce much more heat in the brakes than street vehicles, boiling the fluid is much more likely. This chart with the DOT ratings illustrates just how important it is to flush your brake fluids regularly.
| DOT Rating |
Dry Boiling Point |
Wet Boiling Point |
| DOT 3 |
401 |
284 |
| DOT 4 |
446 |
311 |
| DOT 5 |
500 |
356 |
| DOT 5.1 |
518 |
375 |
| Note: All temperatures listed are degrees Fahrenheit |