Is brake fluid flammable? We discuss what brake fluid is and what are the safety precautions to prevent catastrophic fires from occurring.
Although it is not a volatile fluid, brake fluid is flammable. All modern brake fluids are based on polyalkylene glycols, and experiments have found that polyalkylene glycols ignite spontaneously on surfaces that are heated to 734 to 752 degrees Fahrenheit (390 to 400 degrees Celsius).
So if a collision occurs and modern brake fluid splashes into an exhaust system that has a temperature of 734 degrees Fahrenheit or higher, it will ignite immediately.
The ferocity that brake fluid can burn when it comes in contact with a manifold or exhaust system can be so intense that it can spill over to other plastics like air filters and cable covers.
This is unless it dies out quickly. Otherwise, an entire vehicle can be engulfed in minutes. The integrity of the brake fluid reservoir tends to determine whether or not there will be a fireball.
To learn more about brake fluid and its flammable properties, read on as we discuss what brake fluid is and what safety precautions are to prevent catastrophic fires from happening.
What is brake fluid?
Brake fluid is a hydraulic fluid that moves certain particles within your vehicle’s brake system. Without brake fluid, you won’t be able to stop your vehicle when you want to.
Brake fluid is necessary in cars, buses, trucks, motorcycles, and even certain bicycles. To ensure a vehicle’s brakes are working properly, they need to be maintained, including the brake fluid.
Brake fluid should be inspected by a professional to make sure the brakes are working well enough. If you have the knowledge to do it yourself then this is also acceptable.
But, you should always be very careful when checking the brake fluid and the non-flammable condition of your brakes.
types of brake fluids
There are three varieties of brake fluid currently available on the market. These are:
- point 3
- point 4
- point 5
DOT stands for the US Department of Transportation and there is also a DOT 5.1 which is glycol based but with similar standards to DOT 5. It also has the properties of silicone based hydraulic fluids.
Both DOT 3 and DOT 4 come with glycol based fluids while DOT 5 is silicone based.
DOT 3 and DOT 4 can absorb water, but DOT 5 cannot. This is crucial when we consider the billing point for brake fluid. Hydraulic systems rely on compressed fluids to produce power and force. Liquids then condense while gases are compressible.
If the brake fluid turns to gas or boils, it will not be able to transmit enough force to power the hydraulic system.
Therefore, when it comes to brakes, they can be completely disabled. This is why you need to make sure you have the correct brake fluids with the correct properties for the vehicles.
So is brake fluid flammable?
Brake fluid is flammable, but it does burn slowly. The three main variations of brake fluids (DOT3, DOT4 and DOT5) burn but, compared to gasoline, do not burn as quickly or explosively.
Brake fluid tends to burn in slow motion, like vegetable oil, but a bit faster than the average candle wax burns.
To understand why and how brake fluid is flammable, we must consider its components and properties.
Ethyl Glycol Alcohol-based fluids are flammable and can burn quite well. Silicone-based brake fluids have also been found to support combustion despite some brands claiming they are non-flammable.
As we said, its flammability is not as explosive as gasoline or other volatile liquids. Instead, it burns similar to vegetable oil with a small flash of flame.
You can also find some mineral oil-based brake fluids that are also quite flammable and burn similar to candle wax or baby oil.
So the question remains: can brake fluid cause a fire? Well, although it is flammable, it actually has a low ignitability when it is the main cause of a fire.
To understand its flammability, we need to explore its flash point. This is the temperature at which a flammable substance turns to vapor and burns.
The flash point of a brake fluid is very high, from 210 to 375 degrees Fahrenheit (98.8 to 190 degrees Celsius), but this depends on the type.
At normal temperatures, brake fluid does not ignite because it has a high autoignition temperature of 540 to 675 degrees Fahrenheit (282 to 357 degrees Celsius).
If brake fluid burns in an exhaust manifold during an accident, it will cause a fire that can spread to other vehicle components. Therefore, you must be very careful when handling brake fluid near sources of fire.
Furthermore, brake fluid is also quite corrosive and toxic. This means that it can go through metal parts very easily given the right conditions.
The glycol variety of such hydraulic fluids alone can strip car paint if it comes in contact with it.
So what about DOT 4 brake fluid? As a polyglycol ether based hydraulic fluid, DOT 4 can burn at high temperatures. Its flash point is on the low end of the 210-375 degree Fahrenheit range.
This means it will burn easily compared to silicone based fluids. If exposed to temperatures from 540 to 675 degrees Fahrenheit, it can even self-ignite.
DOT 3 brake fluid is also flammable because it is a glycol based fluid. It has a boiling point of 483 degrees Fahrenheit (250 degrees Celsius), making it classified as moderately flammable with a rating of only 1.
Its flash point is relatively low at 230 degrees Fahrenheit (110 degrees Celsius), which means it can easily ignite, especially when compared to other varieties of brake fluid.
In summary
Brake fluid is one of the most important components of a vehicle’s brake and clutch system. It plays a vital role in transferring power throughout a vehicle’s performance.
However, it can also burn when at high enough temperatures, leading to dangerous situations.
Since it is a derivative of ethyl glycol, care must be taken when handling brake fluid. If there is an open source of fire or a hot item nearby, it could catch fire. It is also toxic and can corrode your vehicle’s paint.
This is why you should be aware of the different types of brake fluids to ensure you choose the right one for your vehicle.
Is DOT 3 brake fluid flammable?
Yes, DOT 3 brake fluid is moderately flammable with a flammability rating of 1. DOT 3 brake fluid is flammable because it is a glycol based fluid. It has a low flash point of 230°F, so it will burn quite easily, much faster than other variants of brake fluid.
Before we discuss why brake fluids are flammable, let’s understand their different types and compositions. There are mainly three models of brake fluid: DOT 3, DOT 4 and DOT 5. The term DOT refers to the (United States) Department of Transportation.
DOT 3 and DOT 4 brake fluids are glycol based. These are flammable and can sustain a fire. Its flammability is not as dangerous or explosive as that of other liquids in a vehicle such as gasoline; instead, they burn like vegetable oil, holding a small flicker of fire. There are also mineral oil-based brake fluids, which are just as flammable and burn like wax.
DOT 3 brake fluid is highly flammable as it has a low flash point (the temperature at which the fluid gives off vapors that can burn) of 230°F. This is much higher than gasoline (around -45°F), but can still pose a risk.
Are DOT 4 and DOT 5 brake fluids flammable?
Yes, DOT 4 brake fluid is also flammable because it is glycol based. It has a flash point of around 210-375°F (generally around the lower limit). Unlike DOT 4, DOT 5 is a silicone-based brake fluid and is not as easily flammable. Some brands even claim to make non-flammable brake fluids, even though reports indicate otherwise.
DOT 4 brake fluid, like DOT 3, is ethyl glycol based and therefore flammable. It has a low flash point, which is usually around the lower limit of 210-375°F. It can also turn on automatically at temperatures around 540-675°F.
auto-ignition refers to the lowest temperature at which a substance will spontaneously ignite without an external ignition source (such as a spark or flame). Therefore, at around 540-675°F, DOT 4 brake fluid will self-ignite or burn on its own.
Unlike the DOT 3 and DOT 4 variants, DOT 5 is a silicone-based brake fluid. Due to this, it has a comparatively higher flash point and is therefore less flammable. However, it will also burn when exposed to high temperatures, despite some companies claiming to make non-flammable brake fluids.
Any of the brake fluids, even DOT 3, will not burn under normal conditions. However, in the event of an accident,these can catch fire, which can spread to other parts of the vehicle. Care should also be taken when handling brake fluids, especially near sources of fire, as they can easily ignite.
Related FAQ
What is a brake fluid flash point?
Flash point is the temperature at which brake fluid vaporizes and can burn. The flash point of brake fluid is 210 to 375 degrees Fahrenheit. Brake fluid has a high flash point, which means that brake fluid is flammable. It has higher flash points than liquids like gasoline with a flash point value of 40 degrees Fahrenheit. However, glycol-based DOT3 and DOT4 have lower flash points compared to the silicon-based DOT5 flash point value.
How many types of brake fluid?
Brake fluids are mainly of four types according to the classification given by the US Department of Transportation (DOT). These are:
- dot3
- DOT4
- DOT5.1
Most fluids come under DOT3, DOT4, or DOT5.1. These brake fluids tend to absorb moisture from the air and therefore keep it airtight.
DOT3 is the standard brake fluid on the market, which is an economical, glycol based brake fluid. On the other hand, DOT3, DOT4 and DOT 5.1 are glycol based fluids while DOT 5 is a silicone based fluid. The main difference between these is that DOT 3, DOT 4 and DOT 5.1 are water absorbent. While DOT 5 is not.
However, if you are using any of these, I recommend against using DOT 5 fluid in vehicles that support DOT3 and DOT 4. Therefore, it is critical to read the manufacturer’s manual before choosing your brake fluid.
Is DOT 3 brake fluid flammable?
Yes, being glycol based, this brake fluid is flammable. It is the most common brake fluid, having a flash point of 230 degrees Fahrenheit. Therefore, it catches fire quickly compared to other brake fluids. Also, the boiling point of this fluid is 250 degrees Celsius. Therefore, it has a rating of 1 and is classified as moderately flammable.
Is DOT 4 flammable?
Yes, DOT 4 brake fluid is flammable. It is a polyglycol based hydraulic brake fluid that is water absorbent. Also, the flash point of this brake fluid is 210 to 375 degrees Fahrenheit, which means it can burn quickly at high temperatures. They burn out sooner than silicone-based brake fluid. When temperatures exceed 540-675 degrees Fahrenheit, DOT4 fluid burns itself.
Is Prestone brake fluid flammable?
prestone brake fluid It is a high temperature synthetic fluid that lasts longer and provides maximum safety. Therefore, it is less flammable compared to other standard DOT brake fluids. As a result, Prestone prevents overheating and fading of the brakes. Also, Prestone provides superior braking performance compared to others. The company claims that it is not flammable as it has a very high flash point temperature value.
What car fluids are flammable?
Your car releases a lot of fluids that burn unintentionally. There are many fluids, such as engine coolant, windshield washer fluid, and automatic transmission fluid, that can start a fire in your car. Also, a lot of research and experiments have been done to check which fluid is flammable and which is not. Test and studies suggest that motor oils, brake fluids, steering fluids, and coolants can also cause a fire in your car. However, there are almost all fluids that catch fire under certain circumstances.
Q: What is the flash point of brake fluid?
When looking at the flammability of various liquids, you should look at their flash point. Brake fluid has a flash point of 210 to 375 degrees Fahrenheit. The flash point is the temperature at which a liquid turns into a vapor capable of sustaining a flame. The flash point of brake fluid is quite high, which means that it is less flammable compared to other volatile flammable liquids like gasoline, which has a value of -40 degrees Fahrenheit. Silicone-based DOT 5 brake fluid has a higher flash point, while glycol-based brake fluid has lower values; therefore, they are more flammable.
Q: Is DOT 4 brake fluid flammable?
DOT 4 is a polyglycol ether based hydraulic fluid and will burn if exposed to high temperatures. It has a flash point on the lower side of the 210-375 degree Fahrenheit limit, which means it will burn easily compared to silicon-based varieties.
When exposed to temperatures from 540 to 675 degrees Fahrenheit, it will self-ignite.
Q: Is DOT 3 flammable?
Yes, DOT 3 brake fluid is flammable as it is a glycol based fluid. It has a boiling point of 250 degrees Celsius and is classified as moderately flammable, with a rating of 1. It has a low flash point of 230 degrees Fahrenheit, which means it will ignite easily compared to other varieties of brake fluid.
Q: Can brake fluid start a fire?
Yes, brake fluid is flammable and when exposed to high temperatures it can cause a fire. According to tests, spraying DOT 3 brake fluid into a hose heated to 1,000 degrees Fahrenheit caused the fire. Brake fluid will burn, but at a lower intensity compared to other volatile fluids.
Q: Do chlorine and brake fluid explode?
When you mix bleach and brake, an explosive reaction will occur that can create a fireball. If you use pool chlorine, which is calcium hypochlorite, and mix it with brake fluid, you’ll notice a latency period, followed by a hissing and fiery explosion. Brake fluid is a glycol polymer and has a hydroxyl group, which chlorine oxidizes. Chlorine is a powerful oxidizing agent, and its power is the cause of the violent reaction.
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