Recently, a Middle Eastern customer asked about brake fluid selection and compatibility. Given the diversity of brake fluid types available on the market today, this is understandable. I have previously written about FMVSS 116 and DOT 3, DOT 4, DOT 5.1, etc., so today I will focus on SAE J1703.
First, let’s clarify that brake fluid is primarily regulated by three internationally recognized standards organizations.
Society of Automotive Engineers (SAE)
SAE classifies brake fluid into three grades: SAE J1703, SAE J1704, and SAE J1705.
Federal Motor Vehicle Safety Standards (FMVSS)
The U.S. Federal Motor Vehicle Safety Standards (FMVSS) categorizes brake fluid into DOT 3, DOT 4, and DOT 5. DOT 5 is further divided into two categories: DOT 5 (silicone-based brake fluid) and DOT 5.1 (non-silicone-based brake fluid). DOT stands for the U.S. Department of Transportation (DOT).
International Organization for Standardization (ISO)
In addition to DOT grades, ISO classifies brake fluids according to ISO 4925: Grade 3, Grade 4, Grade 5.1, and Grade 6. ISO 4925 Grade 6 fluids are typically referred to as low-viscosity brake fluids.
Characteristics and Applications of SAE J1703 Brake Fluid
SAE J1703 brake fluid is a non-petroleum-based brake fluid primarily composed of ethylene glycol, ethylene glycol ether, and appropriate amounts of corrosion inhibitors and antioxidants. This formulation provides excellent lubricity, thermal stability, and corrosion resistance, ensuring stable operation of the braking system under high-temperature or high-load conditions.
The SAE J1703 standard is applicable to most motor vehicles equipped with hydraulic braking systems, particularly those using rubber cups and seals made from styrene-butadiene rubber (SBR) or ethylene-propylene-diene terpolymer (EPDM). These materials maintain good compatibility when in contact with J1703 brake fluid, preventing seal aging or swelling and thereby extending the service life of the braking system.
It is important to note that SAE J1703 brake fluid is not suitable for use in extreme low-temperature environments, such as the Arctic region. This is because its low-temperature flow properties may not meet the performance requirements under extremely cold conditions. In such regions, it is typically recommended to use specially designed low-temperature brake fluids, such as those compliant with the SAE J1704 standard.
The relationship between SAE J1703, DOT 3, and ISO 3
There is a common belief that SAE J1703 brake fluid is equivalent in performance to the DOT 3 standard established by the U.S. Department of Transportation (DOT) and the ISO 4925 Class 3 standard. This claim has some basis, as SAE J1703 and DOT 3 are very similar in key metrics such as boiling point, viscosity, and chemical stability. Both have similar dry boiling points (approximately 205°C) and wet boiling points (approximately 140°C), making them suitable for use in the braking systems of ordinary passenger vehicles and light commercial vehicles. However, despite their similar performance, SAE J1703 and DOT 3 may have minor differences in certain testing standards and certification processes. Therefore, it is recommended to strictly follow the vehicle manufacturer’s recommendations when selecting the type of brake fluid for actual use.
The Importance of Keeping Clean Brake Fluid
The cleanliness of brake fluid directly affects the performance and safety of the braking system. Since J1703 brake fluid is hygroscopic, it absorbs moisture from the air over time, causing the wet boiling point to decrease. This not only reduces the thermal stability of the brake fluid but may also lead to corrosion within the braking system, affecting braking performance. Therefore, maintaining the cleanliness of brake fluid is crucial. Here are some key maintenance recommendations:
Regularly inspect the condition of the brake fluid
By observing the color of the fluid in the brake fluid reservoir, you can preliminarily assess its cleanliness. Fresh brake fluid is typically transparent or pale yellow. If the fluid has turned dark or cloudy, it may have been contaminated or exposed to moisture.
Avoid contamination: When adding or replacing brake fluid, use clean tools and containers to prevent dust, oil, or other contaminants from entering the system. Contaminated brake fluid can cause wear on brake system components and may even lead to brake failure.
Store in a sealed container: Unused brake fluid should be stored in a sealed container to minimize exposure to air and reduce moisture absorption.
How often do you need to flush brake fluid
The answer to the question “How often do you need to flush brake fluid” depends on the vehicle’s usage environment, driving habits, and manufacturer recommendations. Generally, the replacement cycle for SAE J1703 brake fluid is as follows:
Normal usage scenarios: For vehicles used for daily commuting or city driving, it is recommended to replace the brake fluid every 2 years or every 40,000 kilometers (approximately 25,000 miles). This is because brake fluid gradually absorbs moisture, leading to a decline in performance.
High-load usage scenarios: If the vehicle is frequently used in harsh environments such as high temperatures, high humidity, or mountainous areas, or for high-performance driving (such as racing), it is recommended to shorten the replacement cycle to once a year or every 20,000 kilometers.
Manufacturer recommendations: The replacement cycle for brake fluid may vary by vehicle model. It is recommended to consult the vehicle’s user manual or a professional technician. For example, some European brands may require more frequent replacements, while certain Japanese brands may allow longer replacement intervals.
The process of replacing brake fluid typically requires specialized equipment and skills to ensure no air remains in the system and all old fluid is completely drained. When replacing, use brake fluid compliant with the SAE J1703 standard and strictly follow the vehicle manufacturer’s specifications.
Important Notes and Summary
When using SAE J1703 brake fluid, the following points should be noted:
Avoid mixing: Different types of brake fluid (such as SAE J1703 and DOT 5) may not be compatible, and mixing them may cause chemical reactions or performance degradation.
Regularly check the boiling point: Professional repair shops can use a boiling point tester to assess the wet boiling point of the brake fluid to determine if replacement is necessary.
Environmental disposal: Used J1703 brake fluid should be disposed of properly to avoid environmental contamination, as its chemical composition may harm soil and water sources.
We offer bulk supply of DOT 3, DOT 4, DOT 4+, and DOT 5.1 brake fluids. All brake fluids comply with FMVSS No. 116, ISO 4925, and SAE automotive brake fluid standards.
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