Brake fluid is a set like that. absolutely all-important to the safe operation of the vehicle, it ‘s besides capable of doing great damage. If even a small amount of it comes in liaison with your skin, you ‘ll immediately feel the moisture being drawn through your pores. Repeated or sustained touch is decidedly not advisable. And if you have the misfortune of spilling some of it onto the paint surfaces of a vehicle, it will about immediately damage the complete, unless it ‘s quickly flushed away with a neutral fluid like water .
even if brake fluid is kept safely contained in a bottle or in the bracken system, it can silent do unplayful damage. But this damage is normally caused by disregard, preferably than send contact with the outside universe. Polyglycol fluids ( like conventional brake fluid ) are hygroscopic, which means they promptly absorb water system vapor from the air ( or your skin ). On average, water accumulates in the brake fluid of a brake system at a rate of 1 % per year.
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That does n’t seem like much, but think about it. A vehicle with 10-year-old brake fluid immediately has brake fluid that contains about 10 % water. This gradual transformation may go unnoticed. The level in the passkey cylinder should normally drop over time, as the brake pads wear. But as the fluid accumulates water, the flat may appear to stay reasonably a lot unaltered. A casual glance at the master cylinder flat might lead a technician to assume that all is well, as the grade would appear within the “ normal ” range. But the fluid in the reservoir ( and the rest of the system ) would no long be arrant, arrant brake fluid .
Over clock time, even this relatively boring water accumulation is enough to lower the fluid ‘s boiling sharpen, which can cause brake evanesce and diminished brake organization operation. Under pressure when the brakes are applied, the roll up water boils and turns to steam inside the brake system. Unlike liquid brake fluid, steam ( like publicize ) is compressible. The brakes languish because the steam momentarily lowers the coerce in the system. accumulate water in the brake fluid besides causes rust and corrosion, which damage the internal parts of the brake system .
Brake systems besides accumulate sludge and metal particles over clock time. Disc brake hoses normally enter the caliper near the top of the caliper body. similarly, the hemophiliac valve is located at the clear of the caliper bore. If sludge accumulates in the caliper behave, it normally sinks to the bottom. During a brake embroider avail, pushing the caliper pistons back into the caliper bores without opening the hemophiliac valves may dislodge some of the sludge and distribute it throughout the system, possibly causing foster damage. similarly, stirring up sludge that has accumulated in the maestro cylinder reservoir by adding fresh fluid may cause it to get into the rest of the organization, including ABS valves and pumps .
Most would agree that it ‘s best to get the old brake fluent out of the arrangement hanker before it ‘s had a casual to do any wrong. But how frequently should it be replaced ? Some vehicle manufacturers specify substitution of the brake fluid as a hindrance alimony item. If a successor agenda is specified, it should be followed. If no specific recommendation is made, common sense should be an adequate guide. All will agree that water, sludge and metallic element particles in brake fluid are not thoroughly things. It comes down to a question of how much can be considered safe and adequate .
If it ‘s meter to replace the brake fluid, we should clarify our terminology. When a bracken system is opened to the standard atmosphere, normally during a part refilling, it ‘s subsequently necessary to bleed the brakes to remove the air out that ‘s been allowed to enter the system. In this case, our primary concern is removing the compressible breeze from the system so the brakes will function to their full potential. As a side benefit, bleeding the system besides forces fresh brake fluid through the organization, so most of the old fluid ( and possibly a large share of the metallic particles and sludge ) will end up getting replaced .
When we need to replace brake fluent that ‘s old and has accumulated body of water and sludge, this is referred to as flushing the brake system. Unless the system has been opened for other service work, we can assume that there is n’t much if any air out in the system. Our primary aim for flushing the system is n’t to remove breeze, but to remove the urine and sludge along with the old fluid, and replace adenine much of it as possible with clean, dry, newfangled brake fluent .
There are at least five ways the job can be accomplished, but some are quicker and some are more effective than others. In all cases, clean brake fluid must be used. Brake fluid accumulates body of water vaporization just as promptly outside the brake organization as it does inside it, so clean fluid should always be dispensed from a newly opened container. New fluid that ‘s been sitting on the shelf for months in an afford container may look scavenge, but rest assured that it ‘s already accumulated an unacceptable total of water system vaporization and should be discarded in a responsible manner.
The beginning means to flush is the gravity method acting. After filling the overcome cylinder with new fluid, the hemophiliac screws at each rack are opened in sequence. Gravity forces the old fluid out of the hemophiliac screw and it ‘s gradually replaced by fresh fluid. While this method acting may be adequate to of replacing much of the old fluid, the low-pressure, drip-drip-drip sequence does n’t do a identical dear job of dislodging any sludge or other material that may have accumulated in the system. On vehicles equipped with ABS, the gravity method besides may not be capable of flushing the honest-to-god fluid out of the ABS components .
The pump-and-hold method builds upon the gravity method. One technician pumps the brake bicycle respective times, then holds the pedal polish to maintain atmospheric pressure in the arrangement. After placing a hose over the hemophiliac screw and directing it into a container, a second technician opens a hemophiliac screw. The pressure in the system forces the old fluid out and the fluid continues to flow until the bracken bicycle hits the deck. This sequence is repeated several times at each wheel until fresh fluid appears at the hemophiliac prison guard .
A one-man variation on this method employs a one-way valve at the hemophiliac hose ( and possibly Teflon videotape on the hemophiliac screw threads ). With the hemophiliac screw open, one technical school can pump the pedal several times, stopping only to replenish the victor cylinder reservoir and move to the following hemophiliac fuck. Like the gravity method, both versions of the pump-and-hold method do not address any fluid trapped inside ABS components .
The vacuum method uses a consecrated vacuum pump to draw the old fluid out of the organization, via the hemophiliac prison guard. The vacuum pump may be hand-operated, workshop air-powered or electric. Some specialize vacuum bleeding equipment uses a pulsate application of the vacuum, presumably to shake easy any debris, sludge or metal particles and encourage it to exit via the hemophiliac fuck. It ’ mho crucial to keep an eye on the chief cylinder reservoir while using this method, as the vacuum heart can identical cursorily suck the system dry, introducing unwanted atmosphere into the system .
The imperativeness method acting applies pressure at the passkey cylinder reservoir, forcing fresh brake fluid into the overcome cylinder, then through the brake lines to the calipers and bicycle cylinders. The sweetheart blackmail that ’ second applied encourages the old fluid, sludge and other debris to exit when the hemophiliac screws are opened. atmospheric pressure and vacuum can besides be combined. low press applied at the master cylinder reservoir keeps it filled with fresh fluid, while vacuum applied at the hemophiliac sleep together encourages the old fluid to leave .
pressure can besides be applied in the rearward steering. In this method acting, a coerce pump is attached to individual hemophiliac screws. Applying pressure forces the erstwhile fluid and debris back through the system, into the master cylinder, then into the overcome cylinder reservoir where it ’ second siphoned away. The advantage of this method is that if there ’ s any atmosphere trapped in the bracken fluent, it will naturally want to float up in the brake fluid. Forcing the fluid back ( and up ) makes it that much easier to evacuate the breeze. On the minus side, change by reversal flush means that all of the old fluid and sludge must pass through the ABS components and victor cylinder on its room to the reservoir. exposure to this stuff, however brief, may not be a adept thing.
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Both the void and pressure methods can be combined with an ABScapable scan instrument to conduct a more thorough blush service. Combined with vacuum or pressure, the pulsing effect created by cycling the assorted ABS pump valves candid and closed with the scan tool will allow you to remove more of the old brake fluid and sediment than would otherwise be possible. This will greatly reduce the casual that ABS components will be damaged by remaining moisture or sediment that ’ south allowed to linger behind .
Your customers probably will not be able to immediately discern the benefits of a completed brake system flush. Their vehicles probably won ’ tstop 50 feetsooner or necessitate appreciably less campaign at the pedal. But if you ’ ve done a proper job of explaining the benefits of this service, they ’ ll at least have the confidence that you ’ ve maintained the cover safety of their vehicles, and more than likely saved them from the evitable expense of ABS or early bracken system componentreplacement.—Karl Seyfert