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More and more shops are performing a variety of fluent bloom services as a method acting of increasing denounce income. broadly, shops purchase a specialized flush machine for each system they want to perform these services on, but this is not always the subject with brake fluid flush. While there are a act of brake fluid flush machines available, it is not necessity to use one to perform a bracken system bloom .
Shops have three general options when they choose to perform a brake system bloom :
Use a dedicate brake system flush machine ;
Use either a pressure or vacuum hemophiliac ; or
Foot bleed the system to flush it .
note : These are listed in the holy order of efficiency .
Most blush machines are designed to allow flying frame-up and semi-unattended operation. These features allow shops to maximize work stream. The same flush can be performed using either a imperativeness or vacuum hemophiliac, but by and large require the technician to stick with the speculate. ad Performing the flush using animal foot bleeding is the least effective of all methods primarily because it ties up two technicians. Foot bleeding in many cases besides results in the lowest quality flower, not because of the method acting, but because of the time spent performing it .
careless whether you are using a flush machine, or pressure or vacuum hemophiliac, there are some techniques you should be mindful of that will enhance the choice of the hot flash. The quality of the flush and the time necessary to perform it are influenced by the invention of the maestro cylinder reservoir. Most modern vehicles use a screw-cap type reservoir that is normally equipped with a float and consociate baffles. This type of reservoir is impossible to drain completely on the vehicle. In most cases, your best campaign will result in 50 % of the fluent being removed. This is not that bad if the vehicle is merely a couple of years old and hasn ’ t suffered the build-up that can occur in the bottom of these reservoirs. If the vehicle has never been flushed, the 50 % of fluid left in the reservoir can be pretty nasty. This fluid and the associated sludge in the penetrate of the reservoir can impact the quality of the flush. ad When faced with this scenario, you have two options. The beginning is to increase the time spent at each roulette wheel in an attempt to get most of the old fluid out of the reservoir. At the very least, this will involve putting enough extra fluid through the system to displace the remaining 50 % in the reservoir. The second choice is to remove the reservoir and clean it off the fomite. This method allows all of the honest-to-god fluid to be removed and the majority of the sludge. Generally, a combination of hot water, brake clean and compressed air is used to clean the reservoir .
The second of these techniques involves changing the fluid flow during the flush work. If the brake bicycle is left in its convention put during the bloom, not all of the old fluid will be removed from inside the master cylinder. figure 1 helps us understand this. The fluid path during both pressure and void bleeding is from the reservoir, through the vent port into the pressure chamber and then out to the system. Leaving the pedal at respite will leave both no-pressure areas of the dominate cylinder full moon of old fluent. Figures 2 and 3 demonstrate this .
visualize 2 shows one lap of a overlord cylinder before a flush is performed. The piston is in its normal status. figure 3 shows the same chambers after a flush is performed. Notice the dark fluid in the no-pressure area. This fluid will mix into the system the beginning clock the brake pedal point is depressed .
The fluid path can be easily changed so all areas of the passkey cylinder are flushed. This is done by installing a brake bicycle depressor so the brake bicycle is depressed about half an edge ( See Figure 4 ). Depressing the brake pedal point moves the elementary cup seal past the vent port which changes the fluid path. The new fluid path will be from the reservoir through the replenish port, into the no-pressure chamber, over the cup seal and then out to the system ( See Figure 5 ). figure 6 shows the master after flushing when using this method acting. It is easy to see the difference .
One of the chief reasons shops give customers for the need to perform a bracken fluid flush involves the ABS. Customers are often told that the flower will help prevent future internal praseodymium ad The process of bleeding at the wheels until clean fluid is seen does not flush all areas of the ABS modulator. During non-ABS brake, many passages in the modulator are closed off to fluid flow. They only come into maneuver during an ABS check where coerce modulation is required. It is in these areas where the fluid blush is most authoritative because this is where many of the valves and little passages are found .
In order to flush these areas of the modulator the valves and/or pump have to be cycled. This process is normally performed through the use of a scan cock, or in some cases a dedicate bleed creature. broadly, the system is flushed and then the modulator is cycled to expel the old fluid and bring new fluid into these areas. once this is done, the organization is bled at the wheels again. not all shops have the equipment necessary to perform this function so it doesn ’ deoxythymidine monophosphate get done. If you don ’ t have the ability to cycle the ABS there is a work round .
once the bleed and flush is arrant, test drive the vehicle to a loose surface park bunch and engage the ABS half a twelve times. This will draw new fluid into those obscure areas and expel the erstwhile. In an ideal global, you would take the fomite back to the shop and bleed at the wheels again to remove the honest-to-god fluid that was expelled from the modulator. ad There are besides modulators that are equipped with hemophiliac screws and some that require special bleed procedures. Figures 7 and 8 show two such examples. figure 7 is the Delco VI ABS used on many GM FWD vehicles, while visualize 8 shows the ill-famed EBC4 or 4WAL. Bleeding the Delco VI is aboveboard – you good have to remember there are bleeders on the modulator .
The EBC4 is a different report. Bleeding this system out can be time consuming and requires special steps. Basically, the high coerce accumulators have to be held and the internal bleed screws have to be opened to allow fluid menstruation to the unit ’ s external bleeders. ad indeed what ’ s the moral of the story ? Well it goes like this – fair because you get clean fluid out of the bleeders doesn ’ triiodothyronine mean the system has been properly flushed. In barely a few stops and a couple cycles of the ABS system, there can be adequate old fluent in the system to cause it to fail one of the diligence ’ s lone accept brake fluid tests. The Strip Dip™ is a trial comic strip that quickly identifies the brake fluid ’ s ability to inhibit corrosion. The old fluid left in the reservoir, master cylinder no-pressure chambers and/or ABS modulator can be enough to cause a vehicle to fail the test soon after receiving a flush .
nowadays that we have discussed the affluent end of the process we can move on to bleeding the system. Whenever I talk about air travel and the hydraulic arrangement I have to include Sid. Sid is the name I have given any air in the hydraulic arrangement. I feel it is necessity to put a name and expression to our enemy so I did just that ( See Figure 9 ). any prison term we bleed a system out, our primary objective is to make certain Sid is removed. This undertaking is not a easy as it sounds because Sid has some things going for him. The first gear is that he is sticky. He likes to stick to the versatile inner parts of a brake system which can increase the difficulty in getting him out. The future thing he has going for him is the fact there are hiding places in some systems that make it highly difficult to get him out. The last thing he has going for him involves how the bleed process is performed. If besides many “ shortcuts ” are taken, Sid will remain in the system and cause anything from a low bicycle to premature pad wear depending on the system and where he is left .
Bleeding the arrangement out is normally performed after performing hydraulic service. There are steps that can be taken during the hydraulic military service that can reduce how much of Sid is allowed into the arrangement. Reducing the count of Sid ’ sulfur in the system will make the bleed march a lot easier. ad One of the beginning things to make sure of is to never let the system run dry. Based on the organization ’ second shape, allowing this to happen can create some serious problems when trying to bleed the system out. There are a number of methods to prevent this from happening. When changing calipers or wheel cylinders you can just make the barter cursorily so a minimal sum of fluid is lost .
You can besides install a line lock to prevent the system from draining. When using line locks it is authoritative to use approve tune locks that will not damage the brake hosiery. When the work involves changing upriver components or lines and hoses there is a elementary manner to prevent the system from draining. When performing this type of service, install a brake pedal depressor so the brake pedal is applied about 1/2 edge. This covers the vents ports which prevents gravity bleeding. ad As the hydraulic service is performed, the system can be primed by performing graveness bleeding. Gravity bleed should never be used as a stand alone bleed work due to the fact it will not remove all of the breeze or old fluid. Generally, gravity shed blood is done as the make is performed. To perform gravity bleeding, drain and clean the reservoir, if possible, and then fill with new fluid. Start the graveness shed blood at a bicycle that is not being serviced. For model, if the front brakes are being serviced, start the gravity bleed at one of the rears. Keep an center on the clearness of the fluid and the reservoir level. Switch to the opposite rise wheel once the first is complete. move to the front as the work progresses. Gravity shed blood will allow the elementary bleed serve to go flying because the system has been primed .
Many hydraulic systems will not present any difficulties when performing the bleed action. Sid will be removed simply by following the posted shed blood succession and procedures. other systems and components will require extra steps to ensure Sid is removed from the system .
Some calipers have a tendency to trap air in and around the pistons. The Ford F250/350 and E250/350 caliper shown in Figure 10 is an model of this type of caliper. If air is suspected in the caliper, and conventional methods do not yield positive results, use one of, or a combination of, the following methods to remove the breeze : ad
- Unbolt the caliper from its mount and hold the bleeder at the highest point while bleeding.
- Tap on the caliper as the bleed process is performed. This helps to dislodge any trapped air.
- Use the brake pedal to pump the caliper pistons out to their maximum extension making sure not to overextend them. This helps “wipe” the air off the surface of the piston.
Certain brake valves have a inclination to trap air. If air is thought to be trapped in a brake valve, many of them can be bled even though they are not equipped with hemophiliac screws. These valves have to be “ burped ” to remove the at bay atmosphere. typically, technicians will attempt to bleed these valves by cracking the inlet and exit lines. This may work on some types of valves, but not on valves alike to the one shown in Figure 11 .
This is a combination valve used on certain Chryslers FWD vehicles. The valve is where the aslant disconnected takes place. Housed inside of the valve are a coerce differential substitution and two proportioning valves, one for each back wheel. On most vehicles, the valve is located either on the firewall to the leave of the master cylinder or on the unibody frame rail good under the master cylinder. The design of the proportioning valves allows air to become trapped around the proportion valve recurrence spring ( See Figure 12 ). This air normally can not be removed using conventional bleed methods. If publicize becomes trapped it will cause a low spongy pedal point and possibly a brake imbalance which can result in a side-to-side premature pad tire discipline .
The two proportion valves are held in rate by two 3/4″ retain nuts. The atmosphere can be removed using these two nuts.
begin with the proportioning valve that is supplied by the secondary circumference of the maestro cylinder. Loosen the 3/4″ retaining nut until fluid flow is established. ad With the nut loosened, have an assistant depress the brake pedal. While the pedal is being depressed, tap the valve body with a boldness hammer or wooden hammer wield to dislodge any trap breeze .
With the pedal hold in an apply position tighten the retain crackpot. Repeat steps 1 and 2 until no air is seen during the run .
Repeat the above steps with the primary tour proportioning valve .
Bleed at the wheels using the following manufacturers sequence, in this case – RR, LF, LR, RF .
While the above procedures are particular to the valve shown in Figure 11, they can be applied to valves of similar design .
Air can besides get trapped in the master cylinder. If the master cylinder is mounted at an fish, air could be trapped in the high points if the brake line outlets are not at the highest point. The secondary wall socket of the master cylinder, shown in Figure 13, is not at the end of the digest. This presents no trouble if the master cylinder is mounted degree. If this master cylinder is mounted at even the slightest slant, breeze will be trapped in the end of the bore .
If the vehicle is experiencing a low and/or spongy brake pedal and the overcome cylinder is mounted at an angle trapped air might be the cause. Use the steps below to check for trap air. ad Master cylinders mounted at small angles:
Raise the back of the fomite to bring the master cylinder to a level position, as shown in Figure 14 .
caution : Do not raise the vehicle in an insecure manner .
If foot bleeding, crack the line fitting on the secondary coil brake line and have person depress the bracken pedal making certain not to exceed a certain come of bicycle locomotion. Repeat this procedure until no air travel is seen .
Repeat step 2 on the chief brake line. If pedal point altitude and palpate are restored, the haunt is complete .
Master cylinders mounted at sharp angles:
The steps above can not be used to check for air in this type of master cylinder. Raising the rear end of the fomite to a point where the master cylinder is level, would create an dangerous condition. Use the steps below .
Method 1: (use if pressure bleeding)
With the hood adapter and pressure hemophiliac connected, unbolt the headmaster cylinder from the vacuum booster. Gently put the master cylinder so the secondary end of the master cylinder is slightly lower than the primary side ( See Figure 15 ). ad Connect a appropriate container to the forget front wheel ( or the wheel ( s ) supplied by the secondary exit ). Open the hemophiliac screw and let fluid flow .
As fluid flows, tap on secondary coil end of master cylinder to help dislodge trapped tune .
Method 2: (use if Phoenix Injector is available)
unbolt victor from vacuum supporter. Gently position the master cylinder so the secondary end of the overcome cylinder is slenderly lower than the primary side .
Perform RFI™ ( Reverse Fluid Injection ) on one bicycle in each hydraulic circumference. The RFI will take any trapped air up and out the vent port. ad Unconventional Bleed Techniques
When you look up a fomite ’ s bleeding sequence and operation, the information listed is based on using ceremonious methods. While these methods work for a majority of situations they do not work in all cases. RFI or Reverse Fluid Injection™ was introduced by Phoenix Systems some years ago as a method to remove trapped air. RFI is considered a trouble solving march .
This technique involves forcing fluid into the hemophiliac screws to force the fluent and breeze up to the maestro cylinder ( See Figure 16 ). Air naturally wants to travel up therefore this technique takes advantage of this .
Most people who have never heard of this ahead are alarmed because fluid is being pushed up stream. They are concerned about damaging the versatile hydraulic components. There are two points that should be taken into consideration. First, this proficiency is used only as a secondary run technique. The fluent has already been flushed. second, it is done at very low pressures, normally less than 10psi. This prevents forcing any debris upstream. It can use efficaciously on most vehicles equipped with both ABS and conventional brakes. ad RFI™ relies on the fact that the vent port is the highest point in the system. The fluent path is from the hemophiliac fuck, through the lines, hoses and valves into the press chamber of the master cylinder. From there it escapes into the reservoir through the vent port. This is providing the release port is the highest sharpen in the master cylinder. If the master cylinder is mounted level, the air will escape through the vent port. If it is mounted at an angle, it will be trapped in the end of the master cylinder. To use RFI™ bleeding on this vogue of vehicle, the dominate would have to be brought to a level position. Either raise the rise of the vehicle until the master is level, or remove the master cylinder from the vacuum booster and rest it on the booster stud. When raising the vehicle, be careful to do it in a safe manner. Some masters are mounted at excessively severe an angle to allow the use of this method acting. On these, remove the dominate from the booster. ad You might be asking yourself if all this is worthwhile. I think you should first consider that you won ’ metric ton have to do these extra steps on most vehicles. adjacent, think bet on to the survive time you or person else in the denounce spent excessively a lot time bleeding a vehicle out. Spending the extra 10 minutes to undo the victor cylinder would have been time well spent .
In addition to RFI™, the Phoenix Injector allows the practice of another unconventional shed blood proficiency called Pulse Generation. If you have always tapped on a caliper or other brake component while bleeding, you understand what pulse coevals is used for. Air bubbles like to stick to the inner parts of a bracken system. Tapping the component is done to dislodge the atmosphere bubbles. Pulse Generation™ accomplishes the same matter except in a unlike room. Bleeders that allow pulsation generation have to ability to change the atmospheric pressure being applied very quickly which creates “ pulses ” in the system. These pulses break the air out free and it is carried out through the hemophiliac ( see Figures 17 to 19 ). When used in combination with pressure or RFI™ bleeding, it is identical effective in getting the air out. The pulses generated shock the entire hydraulic circuit being bled, not just the component .
The last method I want to discuss involves tune trapped in ABS modulators. As I said before, some modulators require particular tools to allow shed blood. So what do you do if these tools are not available and you suspect air has been trapped in the modulator ? ad The best method to use involves performing the best possible bleed at the wheels to restore the pedal height vitamin a much as potential. If the pedal point can be restored to a point where the vehicle can be driven safely, take it to a loose open park lot and make 6 to 12 hard stops making sure to engage the ABS. As the ABS cycles, it will pump any vent out into the system. Return to the workshop and rebleed at the wheels. Again, I want to stress do not drive a fomite with an insecure pedal .
There is one other technique I want to include before I wrap this article up. One of the problems encountered when selling hydraulic military service in the rust belt areas is the inability to open all bleeders. For exemplar, you sell a accomplished front man bracken job on an older FWD and when you check the rear hemophiliac screws, there is no way they are going to open. One choice would be to sell wheel cylinders, but this is not always virtual. You might say : “ So what, I ’ ll just line lock the movement hoses when I swap the calipers and all will be OK. ” ad This is not constantly the encase because once you remove the channel locks, publicize in the bottom of the hose and caliper move up into the system. It is truthful that on many vehicles the air travel will come right field back down when bleed, but sometimes Sid finds a hiding position, or worse so far, ends up at the opposite roulette wheel in that lap. To prevent this, merely leave the line lock on until you are cook to bleed that bicycle. If foot bleed, apply atmospheric pressure to the pedal, open the hemophiliac and then remove the trace lock. This forces any air down and out. The like is true for blackmail bleeding. Pressurize the system before removing the tune lock.
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ad generally, using some combination of the methods described in this article will allow you to restore about any brake bicycle in a reasonable measure of clock time. Knowing which to use, and in what combination, comes with experience .