Brake fluid is a type of hydraulic fluid used in hydraulic brake and hydraulic clutch applications in automobiles, motorcycles, light trucks, and some bicycles. It is used to transfer force into pressure, and to amplify braking force. It works because liquids are not appreciably compressible.
Most brake fluids used today are glycol-ether based, but mineral oil (Citroën/Rolls-Royce liquide hydraulique minéral (LHM)) and silicone-based (DOT 5) fluids are also available.[1]
Standards[edit]
TR-60D (100-99) Rev.∅ 08/16/04 Page 2 of 19 TABLE OF CONTENTS 1.0 Discussion 2.0 Guide to Compatibility Key 3.0 Chemical Compatibility Guide for Commonly Used Elastomers for O-Rings.
Brake fluids must meet certain requirements as defined by various standards set by international, national, or local organizations or government agencies.
International[edit]
Ever been shopping for brake fluid and wonder what are the pros and cons between using chlorinated vs. Non-chlorinated products? While the main difference may seem obvious, the presence of chlorine, the idea that non-chlorinated versions are always ‘better for the environment’ may be deceiving. Brake fluid itself will not corrode metals, but if the corrosion inhibitors in the fluid break down over time, corrosion could occur. There is the potential for moisture to be present. Aluminum is not automatically immune to corrosion. I have seen aluminum exhibit significant corrosion in many marine situations. You can find any number of demonstrations of it under 'chlorine and brake fluid,' but what you really need is not pure chlorine but a product generally referred to as pool shock.
The International Standards Organisation has published its standard ISO 4925, defining classes 3, 4, and 5, as well as class 5.1 and class 6,[2] reflecting progressively higher performance for brake fluids.
SAE[edit]
The Society of Automotive Engineers SAE has published standards J1703, J1704, and J1705, reflecting progressively higher performance for brake fluids. These have counterparts in the international standard, ISO 4925.
United States[edit]
The Federal Motor Vehicle Safety Standards (FMVSS) under FMVSS Standard No. 116[3] defines grades DOT 3, DOT 4, DOT 5 and DOT 5.1, where DOT refers to the US Department of Transportation. These are widely used in other countries. Their classifications broadly reflect the SAE's specifications, but with local details — Alaska and the Azores for example, have different normal temperature and humidity ranges to consider. DOT 3 is equivalent to SAE J1703 and ISO class 3, DOT 4 to SAE J1704 and ISO class 4, etc.[4]
All approved fluids must be colorless or amber to be acceptable for street use in the U.S, except for DOT 5 silicone, which must be purple.[3]
DOT 4[edit]
While a vehicle that uses DOT 3 may also use DOT 4 or 5.1 (a temperature upgrade) if the elastomers in the system accept the borate compounds that raise the boiling point,[citation needed] a vehicle that requires DOT 4 might boil the brake fluid if a DOT 3 (a temperature downgrade) is used. Additionally, these polyglycol-ether-based fluids cannot be mixed with DOT 5.0, which is silicone based.
As of 2006, most cars produced in the U.S. use DOT 4 brake fluid.
DOT 5[edit]
DOT 5 is a silicone-based fluid and is separate from the series of DOT 2, 3, 4, 5.1. It is immiscible with water, and with other brake fluids, and must not be mixed with them. Systems can change fluid only after a complete system changeover, such as a total restoration.
It contains at least 70% by weight of a diorgano polysiloxane.[5] Unlike polyethylene glycol based fluids, DOT 5 is hydrophobic.[6] An advantage over other forms of brake fluid is that silicone has a more stable viscosity index over a wider temperature range. Another property is that it does not damage paint.[citation needed]
DOT 5 brake fluid is not compatible with anti-lock braking systems. DOT 5 fluid can aerate when the anti-lock brake system is activated. DOT 5 brake fluid absorbs a small amount of air requiring care when bleeding the system of air.[7]
DOT 5.1[edit]
Lack of acceptance of silicone-based fluids led to the development of DOT 5.1, a fluid giving the performance advantages of silicone, whilst retaining some familiarity and compatibility with the glycol ether fluids. DOT 5.1 is the non-silicone version of DOT 5, defined by FMVSS 116 as being less than 70% silicone. Above that threshold makes it DOT 5.
Citroën hydropneumatic suspension[edit]
In the 1950s, Citroën introduced a hydropneumatic suspension system, powered by an engine-driven pump and also used to operate the braking system. This used a Citroën-specific hydraulic fluid. The first fluids were of variable chemistry, and available from various suppliers. Shell Donax D, Lockheed HD19, Castrol HF were some of them. Citroen then attempted to improve and standardise the fluid in 1962 with LHS (Liquide Hydraulique Synthétique), a vegetable/synthetic based fluid. In 1964 this was improved with the fully synthetic LHS2. In 1966 Citroen introduced LHM (Liquide Hydraulique Minéral), a mineral fluid. LHS was hygroscopic and gave problems with internal corrosion. Although the two fluids are incompatible, LHM has been universal since 1967, and some older cars have been converted to use it.[8]
This system was also used on Rolls-Royce and some Maserati models.
Hydragas and Hydrolastic suspension[edit]
Hydragas and Hydrolastic suspension were a widely used form of hydropneumatic suspension, designed by Alex Moulton, and used on British Leyland cars from the 1960s. This system was not engine-driven and did not involve the braking system.
The fluid was a low viscosity fluid based on diluted alcohol.[9]
Brake Fluid And Chlorine Reaction
- 49% alcohol
- 49% distilled water
- 1% triethanolamine phosphate (surfactant)
- 1% sodium mercaptobenzothiazole (stenching agent)
Characteristics[edit]
Brake fluids must have certain characteristics and meet certain quality standards for the braking system to work properly.
Viscosity[edit]
For reliable, consistent brake system operation, brake fluid must maintain a constant viscosity under a wide range of temperatures, including extreme cold. This is especially important in systems with an anti-lock braking system (ABS), traction control, and stability control (ESP), as these systems often use micro-valves and require very rapid activation.[10] DOT 5.1 fluids are specified with low viscosity over a wide range of temperatures, although not all cars fitted with ABS or ESP specify DOT 5.1 brake fluid.[11]For a faster reaction of the ABS and ESP systems, DOT 4 and DOT 5.1 brake fluids exist with low viscosity meeting the maximum 750 mm2/s viscosity at -40 °C°F requirement of ISO 4925 class 6.[2] These are often named DOT 4+ or Super DOT 4 and DOT 5.1 ESP.
Boiling point[edit]
Brake fluid is subjected to very high temperatures, especially in the wheel cylinders of drum brakes and disk brake calipers. It must have a high boiling point to avoid vaporizing in the lines. This vaporization creates a problem because vapor is highly compressible relative to liquid, and therefore negates the hydraulic transfer of braking force - so the brakes will fail to stop the vehicle.[12]
Quality standards refer to a brake fluid's 'dry' and 'wet' boiling points. The wet boiling point, which is usually much lower (although above most normal service temperatures), refers to the fluid's boiling point after absorbing a certain amount of moisture. This is several (single digit) percent, varying from formulation to formulation. Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic (water absorbing), which means they absorb moisture from the atmosphere under normal humidity levels. Non-hygroscopic fluids (e.g. silicone/DOT 5 and mineral oil based formulations), are hydrophobic, and can maintain an acceptable boiling point over the fluid's service life.
Silicone based fluid is more compressible than glycol based fluid, leading to brakes with a spongy feeling.[12] It can potentially suffer phase separation/water pooling and freezing/boiling in the system over time - the main reason single phase hygroscopic fluids are used.[citation needed]
| Dry boiling point | Wet boiling point[a] | Viscosity at -40 °C°F | Viscosity at 100 °C (212 °F) | Primary constituent | |
|---|---|---|---|---|---|
| DOT 2 | 190 °C (374 °F) | 140 °C (284 °F) | ? | ? | castor oil/alcohol |
| DOT 3 | 205 °C (401 °F) | 140 °C (284 °F) | ≤ 1500 mm2/s | ≥ 1.5 mm2/s | glycol ether |
| DOT 4 | 230 °C (446 °F) | 155 °C (311 °F) | ≤ 1800 mm2/s | ≥ 1.5 mm2/s | glycol ether/borate ester |
| DOT 4+ | 230 °C (446 °F) | 155 °C (311 °F) | ≤ 750 mm2/s | ≥ 1.5 mm2/s | glycol ether/borate ester |
| LHM+ | 249 °C (480 °F) | 249 °C (480 °F) | ≤ 1200 mm2/s[14] | ≥ 6.5 mm2/s | mineral oil |
| DOT 5 | 260 °C (500 °F) | 180 °C (356 °F) | ≤ 900 mm2/s | ≥ 1.5 mm2/s | silicone |
| DOT 5.1 | 260 °C (500 °F) | 180 °C (356 °F) | ≤ 900 mm2/s | ≥ 1.5 mm2/s | glycol ether/borate ester |
| DOT 5.1 ESP | 260 °C (500 °F) | 180 °C (356 °F) | ≤ 750 mm2/s | ≥ 1.5 mm2/s | glycol ether/borate ester |
Corrosion[edit]
Brake fluids must not corrode the metals used inside components such as calipers, wheel cylinders, master cylinders and ABS control valves. They must also protect against corrosion as moisture enters the system. Additives (corrosion inhibitors) are added to the base fluid to accomplish this. Silicone is less corrosive to paintwork unlike glycol-ether based DOT fluids.[12]
The advantage of the Citroën LHM mineral oil based brake fluid is the absence of corrosion. Seals may wear out at high mileages but otherwise these systems have exceptional longevity. It cannot be used as a substitute without changing seals due to incompatibility with the rubber.[15]
Compressibility[edit]
Brake fluids must maintain a low level of compressibility, even with varying temperatures to accommodate different environmental conditions. This is important to ensure consistent brake pedal feel. As compressibility increases, more brake pedal travel is necessary for the same amount of brake caliper piston force.
Service and maintenance[edit]
Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic (water absorbing), which means they absorb moisture from the atmosphere under normal humidity levels. Non-hygroscopic fluids (e.g. silicone/DOT 5 and mineral oil based formulations), are hydrophobic, and can maintain an acceptable boiling point over the fluid's service life. Ideally, silicone fluid should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that has used glycol-based fluid (DOT 3/4/5.1) will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there, either. A system filled from dry with silicone fluid does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal. The United States armed forces have standardised on silicone brake fluid since the 1990s. Silicone fluid is used extensively in cold climates, particularly in Russia and Finland.
Brake fluids with different DOT ratings can not always be mixed. DOT 5 should not be mixed with any of the others as mixing of glycol with silicone fluid may cause corrosion because of trapped moisture. DOT 2 should not be mixed with any of the others. DOT 3, DOT 4, and DOT 5.1 are all based on glycol esters and can be mixed, although it is preferable to completely replace existing fluids with fresh to obtain the specified performance.
Brake fluid is toxic[16] and can damage painted surfaces.[17]
Components[edit]
Castor oil-based (pre-DOT, DOT 2)[edit]
Brake Fluid Chlorine And Aluminum Steel
- Alcohol, usually butanol (red / crimson fluid) or ethanol (yellow fluid) (methanol)
Glycol-based (DOT 3, 4, 5.1)[edit]
Silicone-based (DOT 5)[edit]
See also[edit]
References[edit]
- ^'Chapter 7 : Basic Hydraulic System Theory'(PDF). Peterverdone.com. Retrieved 2018-07-06.
- ^ ab'ISO 4925:2005 - Road vehicles -- Specification of non-petroleum-base brake fluids for hydraulic systems'. www.iso.org.
- ^ ab'Code of Federal Regulations, § 571.116 Standard No. 116; Motor vehicle brake fluids'.
- ^'Viscosity of Automotive Brake Fluids'. Anton Paar Wiki. Retrieved 2018-05-25.
- ^Standard No. 116; Motor vehicle brake fluids Code of Federal Regulations, Title 49 - Transportation, Chapter V - Part 571 - Federal Motor Vehicle Safety Standards (49CFR571), Subpart B, Sec. 571.116 Standard No. 116; Motor vehicle brake fluidsArchived 2008-12-08 at the Wayback Machine
- ^'What are the different types of brake fluid?'. How Stuff Works. 2008-12-01. Retrieved 2018-08-12.
- ^'DOT 5 Brake Fluid: Not for ABS'. www.freeasestudyguides.com.
- ^Jackson, Tony; Bardenwerper, Mark L. (March 2016). 'Revised Summary of Citroën Hydraulic Fluids'. citroen.cappyfabrics.com.
- ^'Hydragas suspension technical data'. Hydragas Register.
- ^'Brake Fluid Exchange and Technology'. Partinfo.co.uk. Retrieved 2018-05-16.
- ^'Brake Fluid'. Trwaftermarket.com. Retrieved 2018-05-26.
- ^ abcd'DOT Brake Fluid vs. Mineral Oil'. Epicbleedsolutions.com. Retrieved 2018-05-25.
- ^'49 CFR 571.116 - Standard No. 116; Motor vehicle brake fluids'. Gpo.gov. Retrieved 2018-07-06.
- ^'Viscosity of Automotive brake fluid – viscosity table and viscosity chart :: Anton Paar Wiki'. Anton Paar. Retrieved 2018-07-06.
- ^'AN EXPLANATION OF BRAKE AND CLUTCH FLUIDS'. Xpowerforums.com. Retrieved 2015-05-26.
- ^'MSDS for DOT 3 brake fluid'(PDF). Online.petro-canada.ca. Retrieved 2012-06-04.
- ^'General Tips'. Total Motorcycle. Retrieved 2018-05-25.
External links[edit]
The unspoken law of the universe dictates that if an activity is dangerous, someone will try it. Human nature, right? When someone puts boundaries on what you can or cannot do, curiosity says, “question that, fool!” From ‘Do not feed the animals’ to igniting hairspray with a lighter, nothing is too frightening (or too outlandish) to defy.
Grant Thompson, better known as “The King of Random”, conducts weekly experiments on his YouTube channel that do the exact opposite of the warnings on the back of the box. With a passion for science and blowing things up, Grant manages to create content that is informative, forehead slapping and absolutely entertaining.
Pool Chlorine + Brake Fluid = FIRE
As usual, Grant picks a random request from the comments section of his past YouTube videos and turns it into a 5-10 minute feature. In this particular video, he explores the reaction made by mixing everyday pool chlorine with car brake fluid.
To start, Grant buys a 73% concentrate of pool chlorine and some DOT 3 brake fluid. The fluid contains a mix of glycol ethers which, when combined with calcium hypochlorite (or chlorine), can lead to some interesting results.
That’s what I’m talking about. After filling the bottom of a glass with half an inch of chlorine, he mixes it with the brake fluid. While there seems to be nothing going on for the first minute or so, the mixture suddenly combusts with an audible “POP!” and sends a pillar of flame sky high. Good for celebrating the Fourth of July, a birthday, a new haircut or your cat getting rid of that hairball.
Upon closer inspection, Grant explains the glycol ethers present in the brake fluid are flammable but are separated by oxygen molecules, making them harder to ignite and safe to use on your brakes.
This changes once the fluid is mixed with chlorine. By breaking down the glycol ethers into smaller aldehydes, they start to react with the oxygen and the pool chlorine and combust due to the heat produced. It takes some time for the ethers to break down (which explains the lack of an immediate flame), but soon the area is set ablaze and littered with bits of solidified brake fluid ash.
Whereas some people would be fumbling for a fire extinguisher, Grant instead devises two more experiments: one mixture of chlorine and brake fluid in open air, and another in a plastic bottle.
After throwing caution to the wind and mixing the volatile components with his finger, the mixture goes up in flame at a faster time of 54 seconds. Grant fails to explain this, but the abundance of oxygen in the air could possibly be the cause of this preemptive combustion.
But this pales in comparison to the mixture in the plastic bottle. Though it takes the same amount of time as the glass experiment, the flame that sprouts out from the nozzle is far more violent and rockets up to roof height. Most likely due to the small opening, the flame becomes more concentrated and ends up melting its container.
These components may be common, but the reaction they produce is just out of this world! Even though Grant does this at home, you should definitely take the necessary precaution and, yeah, have a few fire extinguishers nearby. While I don’t condone any act that leads to bodily harm, you can find Grant Thompson’s project PDFs, as well as more of his videos, over on his webpage.
brake fluidcombustionglycol etherGrant ThompsonKing of RandomKoRpool chlorine0AuthorCarlos ZotomayorCarlos wrestles gators, and by gators, we mean words. He also loves good design, good books, and good coffee.Prev Post