Automotive Experiences

Articles

Effect of Moisture Content on Boiling Point Characteristics and Bubble Formation in DOT 4 and 5.1 Brake Fluid

Setya Wijayanta , Dzaki Putra Prakosa

Published
July 19, 2026

Vol. 9 No. 2 (2026)
Pages 490-506

DOI

Open Access
Share

Abstract

The performance of hydraulic braking systems is strongly influenced by the condition of brake fluid, particularly boiling point and tendency to form vapor bubbles that may lead to vapor lock. Glycol-based brake fluids, such as DOT 4 and 5.1, are hygroscopic, causing moisture content to increase over their service life. Therefore, this study aimed to examine the effect of moisture percentage on boiling point and bubble formation characteristics of DOT 4 and 5.1 brake fluid. An experimental method was applied by adding distilled water to brake fluid at varying concentrations of 0%, 1%, 2%, 3%, and 4%, followed by gradual heating. The boiling point was recorded using a temperature sensor connected to a data logger. At the same time, bubble formation was visually observed during the heating process using a high-speed camera with a frame rate of 240 fps. The recorded images during the analysis were subsequently examined using ImageJ processing software. The results showed that increasing moisture content led to a significant reduction in boiling point for both types of brake fluid. At identical temperature levels, fluids with higher moisture content indicated larger bubble volume formation. These results indicated that moisture content played a critical role in degrading the thermal performance of brake fluid and increased the risk of vapor lock in automotive braking systems.

Keywords

Brake fluid; Moisture content; Boiling point; Vapor lock

References

  1. [1] World Health Organization, “Global status report on road safety 2018,” Geneva, 2018.
  2. [2] Tempo, “Korlantas Rilis Data Kecelakaan Lalu Lintas 2024: Naik Nyaris 8 Kali Lipat, Korban Jiwa 27 Ribu,” Tempo, 2025.
  3. [3] T. Gillespie, Fundamentals of vehicle dynamics. SAE international, 1992.
  4. [4] Komite Nasional Keselamatan Transportasi, “Laporan investigasi kecelakaan lalu lintas dan angkutan jalan: Kecelakaan tabrakan beruntun truk tronton KT 8534 AJ di Simpang Rapak, Kota Balikpapan, Provinsi Kalimantan Timur,” Jakarta, 2022.
  5. [5] R. Limpert, Brake Design and Safety. SAE International, 2011.
  6. [6] R. B. GmbH, Automotive Handbook, 10th ed. Wiley, 2018.
  7. [7] X. Xiao, Y. Yin, J. Bao, L. Lu, and X. Feng, “Review on the friction and wear of brake materials,” Advances in Mechanical Engineering, vol. 8, no. 5, May 2016, doi: 10.1177/1687814016647300.
  8. [8] I. Barabás, A. Todoruț, and N. Cordoș, “Estimation of Boiling Points of Brake Fluids,” in CONAT 2016 International Congress of Automotive and Transport Engineering, Cham: Springer International Publishing, 2017, pp. 209–216. doi: 10.1007/978-3-319-45447-4_24.
  9. [9] S. Wijayanta, F. Humami, H. Wibowo, K. A. Kristiawan, and W. S. Lazuardi, “Pengaruh Kadar Air di Dalam Brake Fluid Terhadap Karakteristik Gelembung pada Proses Pemanasan Brake Fluid,” Jurnal Rekayasa Mesin, vol. 15, no. 1, pp. 443–454, May 2024, doi: 10.21776/jrm.v15i1.1705.
  10. [10] P. Owusu-Ansah, T. Alhassan, A. Frimpong, and A. Agyei Agyemang, “Survey of the Causes of Brake Failure in Commercial Mini-buses in Kumasi,” Research Journal of Applied Sciences, Engineering and Technology, vol. 7, no. 23, pp. 4877–4882, Jun. 2014, doi: 10.19026/rjaset.7.878.
  11. [11] Y. A. Çengel and A. J. Ghajar, Heat and Mass Transfer: Fundamentals and Applications, 6th ed. New York: McGraw-Hill Education, 2020.
  12. [12] G. E. Totten, Handbook of Lubrication and Tribology, 2nd ed. New York: CRC Press, 2006.
  13. [13] P. J. Blau, Friction Science and Technology, 2nd ed. CRC Press, 2009.
  14. [14] S. Wijayanta, D. Alwansyah, W. S. Lazuardi, W. D. Fauzi, H. Wibowo, and F. Humami, “Design and Development of Vapor Lock Detection to Prevent Brake System Failure,” Jurnal Teknologi Transportasi dan Logistik, vol. 5, no. 1, pp. 67–80, Jun. 2024, doi: 10.52920/jttl.v5i1.246.
  15. [15] S. Bako, T. Usman, E. P. Mijinyawa, and S. I. Igbax, “An Overview of Hydraulic Brake Fluid Contamination,” in Conference: ISTEAMS International Multidisciplary Conference (SMART 2019), Ogun, Nigeria, 2019. doi: 10.22624/AIMS/iSTEAMS-2019/V15N1P5.
  16. [16] H. Heisler, Vehicle and Engine Technology, 2nd ed. Society of Automotive Engineers, 1999.
  17. [17] Y. A. Çengel, Introduction to Thermodynamics and Heat Transfer, 2nd ed. McGraw-Hill, 2014.
  18. [18] Theodore L. Bergman, A. S. Lavine, F. P. Incropera, and D. P., Fundamentals of Heat and Mass Transfer, 8th ed. Wiley, 2017.
  19. [19] R. C. Gonzalez and R. E. Woods, Digital Image Processing, 4th ed. Pearson, 2018.
  20. [20] G. Mladenov, N. Kuzmanov, and V. Hristov, “Research on and Analysis of Brake Fluid Impact on Brake System Performance,” in The 14th International Scientific Conference TechSys 2025—Engineering, Technologies and Systems, Basel Switzerland: MDPI, Jul. 2025, p. 27. doi: 10.3390/engproc2025100027.
  21. [21] ASTM International, “Standard Specification and Temperature–Electromotive Force (EMF) Tables for Thermocouples,” West Conshohocken, 2017.
  22. [22] R. Jaiswal, B. M. E. Moldestad, M. S. Eikeland, H. K. Nielsen, and R. K. Thapa, “Image Processing and Measurement of the Bubble Properties in a Bubbling Fluidized Bed Reactor,” Energies, vol. 15, no. 21, p. 7828, Oct. 2022, doi: 10.3390/en15217828.
  23. [23] J. E. Hunter, S. S. Cartier, D. J. Temple, and R. C. Mason, “Brake Fluid Vaporization as a Contributing Factor in Motor Vehicle Collisions,” in SAE International, Feb. 1998. doi: 10.4271/980371.
  24. [24] M.-J. Kao, D.-C. Tien, C.-C. Ting, and T.-T. Tsung, “Hydrophilic Characterization of Automotive Brake Fluid,” Journal of Testing and Evaluation, vol. 34, no. 5, pp. 400–404, Sep. 2006, doi: 10.1520/JTE14254.
Article Metrics
124
Views
24
Downloads

SCITE

DIMENSIONS

Publication Information
Published July 19, 2026
Section Articles
Copyright Copyright (c) 2026 Dzaki Putra Prakosa, Setya Wijayanta
License Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
Keywords
  • Brake fluid
  • Moisture content
  • Boiling point
  • Vapor lock