Patent Publication Number: US-2007095422-A1

Title: Brake flush machine

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention is related in general to the field of automotive maintenance systems. In particular, the invention consists of a brake flush machine that allows sequential flushing of a vehicle&#39;s brake lines and anti-lock braking system (“ABS”).  
      2. Description of the Prior Art  
      Anti-lock brake system (ABS) design utilizes multiple hydraulic passageways and valving that restricts fluid movement. This means that fluid flowing through the system will be limited and may take excessive time to properly flush the system. The pressure that can be exerted on the system is limited by the master cylinder reservoir adapter. The adapter connects the pressurized fluid from a brake flush machine to the master cylinder reservoir to the brake system. Most reservoirs are a composite or plastic material and cannot be exposed to pressures above 20 psi without deforming the shape of the reservoir and causing leakage. Most brake flush machines limit master cylinder reservoir pressure to 12-18 psi to prevent leakage. The low pressure also makes removing brake fluid contamination more difficult.  
      In addition, the fluid does not move through each wheel system equally, but it will take the path of least resistance. Some brake flush machines flush all the wheels at the same time. A machine designed to flush all the wheels at the same time may experience an unequal system flush. This means that one part of the system may experience minimal fluid flow, which will not provide a proper flush.  
      Isolated flush machines isolate different parts of the system to control fluid flow. This allows the machine to force fluid though the more restrictive circuits. The downside is that the flush time is lengthened because the flow is isolated to a part of the system and not all the wheels at the same time. A properly isolated flush could take 2-3 times longer to move the same amount of fluid as an all-wheel flush, keeping in mind that the all-wheel flush also experiences an unequal system flush.  
      Empirical testing using Strip Dip® brake fluid test strips has shown that it takes approximately ½ gallon of brake fluid flushed equally through the system at sufficient pressure and flow to attain a proper flush to remove contaminants. Most all wheel flush machines use ½ gallon fluid container and operate for 10-12 minutes. The last minute or two of the cycle removes whatever fluid is left in the container and dumps it into the waste container so that the service uses ½ gallon of brake fluid each time. This does not mean the ½ gallon of brake fluid was flushed through the system, but only that ½ gallon of brake fluid was consumed. The actual flush may have used 1 quart of fresh fluid and the other quart was dumped into the waste. The reason this is done is to complete the flush within the allotted time period and consume ½ gallon of brake fluid per service regardless of the quality of flush.  
      There is also a low/no pressure area in many master cylinder designs that is isolated from the normal fluid pathway during a flush. This leaves an area of old fluid that can contaminate the new brake fluid after the flush has been performed. Even if ½ gallon of brake fluid is flushed through the system, the isolated low pressure area can contaminate the brake fluid once the brake pedal is depressed a few times. Depressing and holding the brake pedal exposes the new fluid to the low pressure area. This has been demonstrated again by the use of FASCAR® Strip Dip brake fluid test strips. A candidate vehicle was tested with Strip Dip®, demonstrating a FASCAR® rating of 100. The brake flush was performed using 1/1/2 gallon of brake fluid using proper sequencing and isolation and the brake fluid was immediately tested after the service, which results in a FASCAR® rating of 0. The vehicle is then driven in which the brake pedal is depressed several times during normal braking and a Strip Dip® retest is performed, which results in a FASCAR® rating of 25. It is not a problem with the test strip, but the low/no pressure area was not cleaned during the flush process and the old fluid contaminated the rest of the system.  
      To attain a proper brake system flush, approximately ½ gallon of brake fluid must be flushed through the system at sufficient pressure, circuit isolation, and flow to remove contaminates. In addition, the low/no pressure area of the master cylinder must be exposed to fluid flow to flush that portion of the system to prevent future contamination. An isolated brake flush machine could take as long as 30 minutes to properly introduce ½ gallon of brake fluid sequentially through the system, while current all wheel flush machines operate for 10-12 minutes and waste the unused fluid. Each brake flush machine design has severe design flaws, first is the time to perform service or, second, the quality of the service performed.  
      There are different classifications and standards for brake fluid, D.O.T. 3, 4, 5, and 5.1 (synthetic). D.O.T. 3, 4, and 5.1 brake fluids can be mixed together and perform to at least the minimum specification of the primary fluid. The seals in the brake system are compatible with these fluids. D.O.T. 5 is a silicone based fluid and cannot be mixed with any other type of brake fluid and will void many original equipment brake part warranties if used in a vehicle. D.O.T. 5 is primarily used for off-road use like racing and in motorcycle brake systems.  
      In addition, there are several manufacturers of brake fluids in the same D.O.T. class that have varying performance criteria. Many original equipment manufacturers have their own formulation of brake fluid. Therefore, it is desirable to have a brake flush machine that can be used with various manufacturers&#39; specifications of brake fluid. It is therefore important for the brake flush machine to be able to purge the brake flush machine with fluid used in the last service and prime the brake flush machine with the desired fluid for the next service. This feature gives the user the ability to service a variety of vehicles each with the original equipment manufacturer&#39;s brand of brake fluid.  
      Most late model anti-lock braking systems (“ABS”) require the use of a scan tool to properly bleed and flush the brake system. There are no current brake flush machines that allow the user to use a scan tool while the automated brake flush is performed. It is therefore desirable to have an interface which allows the user to perform various bleed/flush tasks as prompted by the scan tool.  
      Accordingly, it is desirable to have a brake flush system that primes brake fluid into a brake flush machine&#39;s bleed/flush lines in a manner that removes air and different types of fluid from these bleed lines and introduces the correct type of brake fluid. Additionally, it is desirable to have a system of sequentially flushing various bleed lines and ABS systems. It is also desirable to have an easy-to-use interface such as a graphical user interface or combination of graphic symbols or letters, lights, lamps, LEDs, buzzers, and speakers. A method of quickly connecting and disconnecting bleed lines and preventing fluid from flowing in the wrong direction is desirable as well. Other desirable features include utilizing a dual-pump manifold system to pressurize some fluid lines while providing vacuum on others; notifying a user when a low-flow, fluid empty, or system leak situation occurs; utilizing OEM scan tools such as GM Tech 2®; providing troubleshooting and diagnostics for the brake fluid machine; and performing reverse fluid injection, vacuum bleeding, pressure bleeding, and test-bench bleeding using the same bleed lines.  
     SUMMARY OF THE INVENTION  
      The invention disclosed herein utilizes a fluid-distribution system including one or more pumps, a plurality of fluid-distribution nodes, an onboard computer, and bleed/flush lines to sequentially flush a vehicle&#39;s brake system. A purge cycle allows the brake flush machine to remove air, old fluid, or the wrong type of fluid from the machine&#39;s manifold and bleed lines. The plurality of fluid-distribution nodes includes solenoids that are controlled by the onboard computer that allow for sequentially flushing of various bleed lines and the vehicle&#39;s ABS system, if present. Additionally, the fluid-distribution system is capable of closed-loop priming with fluid for the next service.  
      A graphical user interface displays various information and may include a touch screen input device. Alternatively, a user interface may include a combination of graphic symbols or letters, lights, lamps, LEDs, buzzers, and speakers to communicate information to a technician.  
      Quick connect fittings are added to the bleed lines to allow the quick connecting and disconnecting from bleed valves. An optional check valve in each bleed/flush line prevents fluid from flowing in the wrong direction, preventing air or waste fluid from back-flowing into the vehicle&#39;s brake system.  
      A dual-pump sequential control manifold allows the system to pressurize some fluid lines while providing vacuum on others, if desired. This decreases the time necessary to flush the brake system and increases the brake flush machine&#39;s ability to remove contaminants from the vehicle.  
      Another feature of the invention involves utilizing a notification system of graphical screens, lights, lamps, LEDs, buzzers or speakers to notify a user when a low-flow, fluid empty, or system leak situation occurs. Yet another feature is an interface that allows the fluid-distribution system to utilize OEM scan tools such as GM Tech 2®. Another aspect of the invention is a memory device for storing vehicle user manuals or bleed sequences that may be displayed on the GUI. The invention also includes troubleshooting and diagnostics systems for the brake fluid machine itself.  
      Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention comprises the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiments, and particularly pointed out in the claims. However, such drawings, description, and claims disclose just a few of the various ways in which the invention may be practiced.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram illustrating a fluid-distribution system including one or more pumps, a plurality of fluid-distribution nodes, an onboard computer, a user-interface, a waste receptacle, and a plurality of bleed/flush lines.  
       FIG. 2  is a block diagram of a main menu of the user-interface of  FIG. 1 .  
       FIG. 3  is a block diagram of an optional master cylinder cleanout screen of the user-interface of  FIG. 1 .  
       FIG. 4  is a block diagram of an optional safety screen of the user-interface of  FIG. 1 .  
       FIG. 5  is a block diagram of an optional test result input screen of the user-interface of  FIG. 1 .  
       FIG. 6  is a block diagram of an optional system prime menu of the user-interface of  FIG. 1 .  
       FIG. 7  is a block diagram of a fluid-distribution system of the user-interface of  FIG. 1 .  
       FIG. 8  is a block diagram of a brake flush help menu of the user-interface of  FIG. 1 .  
       FIG. 9  is a block diagram of a brake flush status screen of the user-interface of  FIG. 1 .  
       FIG. 10  is a block diagram of a event notification screen of the user-interface of  FIG. 1 .  
       FIG. 11  is a block diagram of a second brake status screen.  
       FIG. 12  is a block diagram of a scantools interface.  
       FIG. 13  is a flow chart illustrating a brake flush algorithm utilizing the fluid-distribution system of  FIG. 1 .  
       FIG. 14  is a block diagram illustrating a fluid-distribution system including one or more pumps, a first, second, and third distribution node, a plurality of three-port valves, and a plurality of bleed/flush lines according to the invention.  
       FIG. 15  is a table indicating the status of the pumps and three-port valves of the fluid-distribution system illustrated in  FIG. 15  during various disparate procedures.  
       FIG. 16  is a block diagram illustrating the fluid-distribution system of  FIG. 15  with an additional fluid-distribution node to facilitate priming the fluid-distribution system and specifically the bleed/flush lines.  
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      This invention is based on the idea of using a fluid-distribution system to selectively flush brake lines, master cylinders, and anti-lock brake (“ABS”) systems or other hydraulic brake components in a vehicle. For the purposes of this application, bleed lines, flush lines, and bleed/flush lines are used interchangeably. Additionally, a manifold or distribution node is used interchangeably to refer to a volume including multiple ports. A three-port valve is used herein to indicate a valve that includes at least three ports. A common port may alternatively be connected to either of the other two ports. Connections may be made from the fluid-distribution system to the vehicle via the vehicles bleed valves and master cylinder, referred to herein as discrete fluid-flow elements.  
      Referring to figures, wherein like parts are designated with the same reference numerals and symbols,  FIG. 1  is a block diagram illustrating a fluid-distribution system  10  including one or more pumps  12 , 13 , a plurality of fluid distribution nodes  14 , a computing device  16 , a user-interface  18 , a waste receptacle  20 , and a plurality of bleed/flush lines  22  and vacuum lines  23 . The primary purpose of the fluid-distribution system  10  is to introduce new brake fluid into a master cylinder and brake lines of a vehicle in a manner designed to force air and contaminated brake fluid out of the master cylinder, calipers, or other hydraulic brake components and brake lines. To aid in the evacuation of air and contaminated fluid, the vehicle&#39;s brake lines typically include bleed valves. Modem vehicles may also include anti-lock braking systems (“ABS”) for varying the pressure of the brake fluid delivered to each brake caliper located at each wheel. These ABS systems may also include bleeder valves for evacuating air and contaminated brake fluid from the ABS system. The pumps  12 , 13  are used to provide positive pressure and/or a vacuum to the plurality of fluid distribution nodes  14 .  
      Various vehicle manufacturers recommend specific brake flush sequences tailored to different makes and models. Using the brake flush machine  10 , isolated brake flush procedures may be performed according to a desired sequence. Independent control of each solenoid valve  28  allows the brake flush machine  10  to isolate individual brake lines, ABS systems, and the master cylinder during the flush procedure. In this way, the fluid-distribution system  10  may better flush air and contaminants from specific portions of the vehicle&#39;s brake system.  
      The computing device  16  may be an embedded processor. Alternatively, the computing device may be a micro-processor, a field-programmable gate array (“FPGA”), an application-specific integrated circuit (“ASIC”), general purpose computer (“CPU”), or programmable logic device (“PLD”). The user interface  18  ( FIG. 1 ) preferably includes a video display  19  such as a cathode ray tube (“CRT”) or computer monitor or any of a variety of graphical touch screens. The user interface  18  may also include an input device such as a keyboard  42  or keypad, a mouse  44 , or a touch-screen monitor  46 . Alternatively, the user interface  18  may include a set of graphics and textual information, lamps, light-emitting diodes (“LEDs”), buttons, and switches.  
      In one embodiment of the invention, the user interface  18  illustrated by the block diagram of  FIG. 2  includes a graphical user interface (“GUI”)  50  including information display screens  52 , menus  54 , and selectable areas or graphical buttons  56 . The graphical user interface  50  is a visual representation of a software application  57  stored in a memory device  17  and accessed by the computing device  16  of  FIG. 1 . If the video display  19  includes a touch-screen monitor  46 , a user may select a displayed item from one of the menus  54  or one of the graphical buttons  56  simply by placing an object or finger in the general area of the displayed item. Alternatively, a user may move a graphical cursor or pointer to the desired location using the keyboard  42  or mouse  44  and depress a switch to indicate the intended choice.  
      The display screen  52  of  FIG. 3  is the main menu  57  of the preferred embodiment of the graphical user interface  50  of the fluid-distribution system  10  including graphical buttons for master cylinder cleanout  58 , master cylinder fill  60 , utilities  62 , help  64 , and brake flush  66 . Selecting the master cylinder cleanout graphical button  58  invokes the information display screen  52  of the master cylinder cleanout menu  68  as illustrated by the block diagram of  FIG. 3 .  
      The master cylinder cleanout menu  68  includes graphical buttons  56  and additional textual information  70  to assist a user in using the brake flush machine  10  properly. Once an activity as been selected, such as initiating a master cylinder cleanout procedure by selecting the start button  72 , optional information screens may be displayed. In  FIG. 4 , the optional information safety screen  74  includes textual information  70  and a graphical compliance indicator button  76  for affirming compliance with proper safety procedure. The fluid-distribution system  10  may be adapted to prevent a user from continuing a brake flush procedure until he has positively indicated his compliance.  
      Additionally, optional data input screens such as the stripdip menu  78  of  FIG. 5  may require that a technician or other user input specific information before proceeding with a brake flush procedure. Here, the stripdip menu  78  includes graphical buttons  56  for indicating the results of a stripdip test that gauges the amount of contaminants in a vehicle&#39;s brake system. This information may be used by the fluid-distribution system  10  to adjust the length of time dedicated to a brake flush procedure. A lower contaminant level may allow for a more perfunctory brake flush, while a high contaminant level may require a more extensive brake flush procedure. The system prime menu  80  illustrated by the block diagram of  FIG. 6  includes textual information  70  and graphical buttons  56  for initiating or bypassing a priming procedure.  
      Once all information safety screen and data input screens have been managed properly, the computing device  16  will initiate a procedure such as priming the sequential control valve manifold  14 , evacuating a master cylinder, or flushing contaminants from a vehicle&#39;s brake lines. This is accomplished by the computing device  16  sending control signals to the pumps  12 , 13  and the solenoid valves  28  ( FIG. 1 ). By regulating which pumps are operative and which solenoid valves are open or closed, the fluid-distribution system  10  can perform any of a multitude of brake flush procedures, as previously indicated.  
      Referring back to the main menu  57  illustrated by  FIG. 2 , selecting the brake flush graphical button  66  invoke the brake flush menu  82  illustrated by  FIG. 7 . Selecting the help graphical button  84  invokes the brake flush help menu of  FIG. 8  which includes additional textual information  70  to aid a technician in the proper use of the fluid-distribution system  10 .  
      The block diagram of  FIG. 9  indicates a brake flush status screen  88  including a dynamic graphical status display  90  and a stop graphical button  92  for interrupting a brake flush procedure. Event notification screens  94 , such as the one illustrated in  FIG. 10 , are displayed when the computing device  16  detects an anomalous condition and temporarily interrupts a brake flush procedure. In this example, a user may either terminate the brake flush procedure, resume the procedure, or correct the problem and resume the procedure. A second brake flush status screen  96 , as illustrated by the block diagram of  FIG. 11 , includes additional textual information  70  and graphical buttons  56  for completing a brake flush procedure.  
      Selecting the utilities graphical button  62  ( FIG. 2 ) from the main menu  57  may invoke optional procedures such as a scan tool interface  98 , as illustrated in  FIG. 12 . Vehicle manufactures sometimes develop automated diagnostic applications called scantools. The fluid-distribution system  10  is designed to interface with these scantools. In an exemplary interface of the invention with scantools, a scantool will prepare the vehicle&#39;s engine and brake controller for a brake system flush. Using input signals from the scantool application, the computing device  16  may prompt the user to flush new brake fluid through isolated branches of the vehicle&#39;s brake system according to a sequence and schedule dictated by the manufacturer.  
      Vehicle manufacturers have created a protocol for communicating with the vehicle&#39;s computer. The tool used to communicate with the vehicle computer is commonly referred to as a scan tool. A scan tool may also be bidirectional, meaning it can directly control or initiate procedures. One such procedure is preparing the ABS system for bleeding and flushing.  
       FIG. 13  is a flow chart illustrating a brake flush algorithm  100  utilizing the brake flush machine of  FIG. 1 . In step  102 , a user initiates a closed-circuit priming procedure. In step  104 , the user selects a brake flush procedure such as master cylinder cleanout, master cylinder fill, or brake flush. Optional steps  106  and  108  include acknowledging proper safety procedures and inputting test result data, respectively. In step  110 , the computing device  16  initiates a brake flush procedure by selectively activating pumps  12 , 13  and opening ports  34  and alternate ports  35 . In optional step  112 , abnormal conditions such as low pressure or low fluid flow are displayed as event notifications screens and in step  114 , completion procedures are displayed for the technician.  
      Other features of the fluid-distribution system  10  include the ability to transfer contaminated brake fluid from the waste receptacle  20 , test the pumps  12 , 13 , and troubleshoot problems with the solenoid valves  28 . Additionally, the fluid-distribution system  10  may be integrated with a brake flush accelerator as described in U.S. provisional patent application Ser. No. 10/981060 which is hereby incorporated by reference.  
      In one embodiment of the invention, as illustrated in  FIG. 14 , a fluid-distribution system  200  includes a first distribution node  202  connected to a first plurality of three-port valves  204 , 206 , 208 , 210 , 212 , 214 . These three-port valves may include solenoid valves that create a first path for fluid flow from their top ports  204   a , 206   a ,  208   a , 210   a , 212   a ,  214   a  and their common ports  204   b , 206   b , 208   b   210   b , 212   b  when the solenoid valves are not energized. In this embodiment of the invention, the first paths may be closed off and second paths created from the common ports to the bottom ports  204   c , 206   c , 208   c , 210   c , 212   c , 214   c  which are, in turn, connected to a second distribution node  216  when the solenoid valves are energized. A second plurality of three-port valves  218 , 220  connect the second distribution node  216  to a third distribution node  222 .  
      A new fluid container  224  is connected to a first pump  226  which is, in turn, connected to the common port  218   b . The common port  220   b  is connected to a second pump  228  which is connected through an optional three-port valve  231  for expelling brake fluid from the system to the first distribution node  202 .  
      The common port  214   b  is connected to a waste container  230  that stores contaminated fluid during normal use. When it is desirable to empty the waste container  230 , the waste container  230  may be purged through the fluid-distribution system  200  and expelled through the optional three-port valve  231 . Alternatively, the waste container  230  may be drained or poured into a container which is external to the fluid-distribution system  200 .  
      The common ports  204   b , 206   b , 208   b , 210   b  are connected by bleed/flush lines  22  to a vehicles bleeder valves (also not shown). The common port  212   b  is optionally connected to a vehicle&#39;s ABS system (not shown). The third distribution node  222  is connected by an optional master/cylinder adapter  232  to a vehicle&#39;s master cylinder  234  Alternatively, the master/cylinder adapter  232  may be replaced with an evacuate gun  236  designed to suck fluid and contaminants from the master cylinder  
      Using this fluid-distribution system  200 , an operator may perform a variety of functions without having to reconfigure hoses and bleed/flush lines, as illustrated in the table of  FIGS. 15 . In the first row, the valves of the brake flush machine are configured so that an operator may evacuate a vehicle&#39;s master cylinder. First, the evacuate gun  236  is placed on a bleed/flush line  22  attached to the third distribution node  222 . Solenoid  220  is not energized, creating a path from the third distribution node  222  to the second pump  228 . Solenoid  214  is energized creating a path from the first distribution node  202  to the waste container  230 . The second pump  228  is turned on. In this manner, a vacuum is created at the master cylinder  234  which pulls brake fluid and contaminants from the master cylinder, through the evacuate gun  236 , through the third distribution node  222 , solenoid  220 , the second pump  228 , the optional three-port valve  231 , the first distribution node  202 , the solenoid  214 , to the waste container  230 . It is noted for completeness that solenoids  204 , 206 , 208 , 210 , 212 , 216  are energized and the first pump  226  is turned off removing the associated bleed/flush lines, the vehicle&#39;s bleeder valves, and the new fluid container  224  from the evacuation procedure.  
      The second row of the table of  FIG. 15  indicates the procedure for filling the master cylinder  234  with new brake fluid from the new fluid container  224 . The first pump  226  is turned on drawing new fluid from the new fluid container  224  through the non-energized solenoid  218 , the third distribution node  222 , and the master/cylinder adapter  232  to the master cylinder. This procedure may also be used to flush a master cylinder when it is disconnected from the vehicle, as in a bench bleed.  
      To flush a single brake line on the vehicle, the procedure of the third row is implemented. The first pump  226  is on, drawing new fluid from the new fluid container  224  through the solenoid  218 , through the third distribution node  222 , to the vehicles master cylinder. The fluid is forced through the vehicles brake system, through a bleed/flush line  22 , through the solenoid  204 , the first distribution node  202 , and another solenoid  214  to the waste container  230 . Likewise, flushing a vehicle&#39;s other brake lines and ABS system, if present, are illustrated in rows four through seven. To flush all of the vehicles brake lines and ABS system simultaneously, the procedure of row  8  is used.  
      To empty contaminated fluid from the waste container  230 , the procedure illustrated in the ninth row is implemented. Solenoids  214 , 220  are energized and the second pump  228  is active drawing the contaminated fluid through solenoid  214 , the second distribution node  216 , the solenoid  220 , the second pump  228 , and the three-port valve  231 . In this instance, the three-port valve  231  is turned so as to expel (“expel”) the fluid from the system, rather than allowing it to pass through (“P/T”).  
      The tenth row of the table of  FIG. 15  illustrates a procedure for vacuuming fluid from the brake lines. In this instance, the first pump  226  is on, pumping new fluid from the new fluid container  224  through solenoid  218 , through the third distribution node  222 , and into the master cylinder  234 . The fluid is forced through the vehicle&#39;s brake lines (not shown) and is extracted from the bleeder valves by a vacuum created by the second pump  228 . Here, the second pump draws the brake fluid through solenoid valves  204 , 206 , 208 , 210 , 212 , through the second distribution node  216 , and the solenoid valve  220 . The fluid is then forced into the first distribution node  202  and solenoid valve  214  into the waste container  230 . This procedure may be alternatively performed without the aid of the pressure supplied by the first pump  226 , as well.  
      Row  12  of  FIG. 15  illustrates a cross-flush process where fluid is introduced into a line and extracted from another line. The second pump  228  simultaneously applies vacuum to the second distribution node  216  and pressurizes the first distribution node  202  in order to pressurize some lines while simultaneously applying vacuum to others. For example, new brake fluid may be introduced through the first pump  226 , solenoid valve  218 , and the third distribution node  222 . This fluid is evacuated through solenoid valves  204 , 208 , 210 , 212  (but not  206 ), partly recirculated through solenoid valve  206  to cross-bleed through the vehicle and partly sent to the waste container  230  through solenoid valve  214 . Many variations of this cross-bleed process may be used to pressurize and vacuum individual wheel lines. Alternatively, this process may be executed with the first pump  226  off.  
      Row  13  of the table of  FIG. 15  illustrates an alternate cross bleed procedure. New brake fluid may be introduced into the vehicle through the first pump  226 , solenoid valve  218 , the second distribution node  216 , and solenoid valve  204 . This fluid is evacuated through solenoid valves  206 , 208 , 210 , 212  and the first distribution node  202  and sent to the waste container  230  through solenoid valve  214 .  
      If the second pump is powered on during the alternate cross bleed procedure, a vacuum is applied to the master cylinder through the third distribution node  222 . The fluid extracted from the master cylinder will be sent to the first distribution node  202  where it is combined with the fluid arriving through solenoid valves  206 , 208 , 210 , 212  and sent to the waste container  230  through the solenoid valve  214 .  
      An optional fourth distribution node  240  is shown in the illustration of  FIG. 16 . Here, the bleed/flush lines are connected from the common ports  204   b , 206   b , 208   b ,  210   b , 212   b  to the fourth distribution node  240  and the priming procedure of the fourteenth row of the table of  FIG. 15  is implemented to prime the fluid-distribution system  200  and the bleed/flush lines  22  with new fluid. Solenoid  218  is not energized and the first pump  226  is activated, drawing new brake fluid from the new fluid container  224  into the third distribution node  222 . A hose  242  connects the third distribution node  222  to the fourth distribution node  240 , allowing the new fluid to flow to the bleed/flush lines  22 , through the solenoids  204 , 206 , 208 , 210 , 212 , through the first distribution node  202 , through solenoid  214 , to the waste container  230 . A valve prevents outflow through the bleed/flush line for the waste cylinder.  
      All of these procedures may be facilitated by either removing the check valves  36  or using an improved check valve  36 . While a traditional check valve maybe used to prevent fluid from flowing from the line as it is removed from the wheel and dropped to the floor, a specialized check valve may prevent reverse fluid flow only when under low pressure. For example, this improved check valve may prevent reverse flow until pressure reaches 1 or 2 psi and then becomes unseated, allowing reverse fluid flow.  
      Those skilled in the art of making fluid-distribution system may develop other embodiments of the present invention. However, the terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.