Brake Fluid Testers for Auto Repair Shops

Frequently Asked Questions About Brake Fluid Testing

Brake fluid changes its properties over time and should be checked regularly in accordance with the manufacturer’s specifications. In particular, the water content and the resulting boiling point are important criteria for evaluation. Here, we answer frequently asked questions about testing, evaluating, and properly handling brake fluid.

• Why should brake fluid be checked?

  Brake fluid transmits hydraulic force between the brake pedal and the wheel brakes.
  
  Conventional glycol-based brake fluids can absorb moisture over time.
  
  This lowers the boiling point, making it easier for vapor bubbles to form under high thermal stress.
  
  Regular inspection helps assess the actual condition of the brake fluid.

• What does “hygroscopic” mean in the context of brake fluid?

  Hygroscopic means that a liquid can absorb moisture from its surroundings.
  
  DOT-3, DOT-4, and DOT-5.1 brake fluids are typically glycol-based and hygroscopic.
  
  The absorbed moisture spreads throughout the brake fluid and affects its properties.

• Why does the boiling point decrease when water is present in the brake fluid?

  Water has a significantly lower boiling point than high-quality new brake fluid.
  
  As moisture absorption increases, the boiling point of the brake fluid therefore decreases.
  
  This is particularly relevant under heavy thermal stress, such as during repeated hard braking or long downhill drives.

• What happens if brake fluid gets too hot?

  If brake fluid that is already contaminated with moisture is heated to a high temperature, vapor bubbles can form.
  
  These bubbles are compressible and can therefore impair hydraulic power transmission.
  
  For this reason, the boiling point is an important parameter in the evaluation of brake fluid.

• How is brake fluid tested?

  That depends on the testing device used.

  Electronic brake fluid testers evaluate the fluid using a specific measurement method and then display, for example:

  • water content
  • boiling point or corresponding boiling point
  • or a recommendation to change the fluid.

  The exact testing method depends on the device model and the type of brake fluid.

• For which brake fluids is the EBT 03.3 suitable?

  The EBT 03.3 supports, among other things:

  • DOT 3
  • DOT 4
  • DOT 4 Plus
  • DOT 5.1
  • DOT 4 Class 4
  • DOT 4 Class 6

  The type of brake fluid specified for the vehicle must be taken into account during the test.

• What does the Leitenberger EBT 03.3 measure?

  The EBT 03.3 is designed for professional electronic testing of brake fluid.

  The device displays:

  • Water content in percent
  • Boiling point in °C
  • Recommendation to replace: Yes/No.

  In addition, the device can be connected via a USB interface to PC software for documenting the measurement results.

• What measurement method does the Leitenberger EBT 03.3 use?

  The brake fluid testers are based on the “impedance measurement method,” adapted to the specific electrochemical behavior of brake fluid.
  
  We examine all brake fluids listed in our EBT meters in great detail in our laboratory before storing the reference values in our meters. One of the test criteria we verify on a laboratory scale is the boiling point of the brake fluid.
  
   

• Can DOT 5 also be tested using any brake fluid tester?

  No.
  
  DOT 5 is typically silicone-based and differs fundamentally from the standard glycol-based DOT 3, DOT 4, and DOT 5.1 fluids.
  
  A testing device may only be used for the types of brake fluid for which it is specifically designed.
  
  DOT 5, for example, is not one of the brake fluid types specified for the EBT 03.3.

• Is water content the same as boiling point?

  No.
  
  There is a correlation between water content and boiling point in glycol-based brake fluids, but the two values are not identical.
  
  The exact boiling point also depends on the type of brake fluid used and its properties.
  
  Therefore, it is advantageous if the testing device takes the specific type of brake fluid into account.

• Does brake fluid need to be changed automatically once it reaches a certain water content?

  A flat-rate percentage limit should not be applied regardless of the vehicle and brake fluid type.

  The following factors are crucial:

  • Vehicle manufacturer specifications
  • Brake fluid type
  • Test results
  • Recommended maintenance interval

  A professional testing device can assist in the assessment but does not replace the vehicle manufacturer’s maintenance specifications.

• Does brake fluid need to be changed according to the maintenance schedule, regardless of the test results?

  If the vehicle manufacturer specifies a fixed replacement interval, it should be followed.
  
  A good test result does not automatically mean that a prescribed maintenance interval can be ignored.
  
  The condition check is an additional diagnostic and documentation tool.

• Where should the brake fluid be checked?

  The test is performed in accordance with the operating instructions for the respective test device.
  
  For electronic workshop testers, a suitable sample—typically the brake fluid—is usually tested at the designated test point.
  
  Care must be taken to ensure that the fluid is not contaminated with water, dirt, or other substances.

• Can a brake fluid tester be tested on its own?

  For devices designed for this purpose, yes.
  
  Leitenberger offers an EBT Checker Set for self-testing its electronic brake fluid testers.
  
  This allows you to verify whether the tester is functioning correctly within the specified test parameters.

• Can the measurement result be documented?

  The EBT 03.3 supports digital documentation.

  Using the USB interface and the accompanying PC software, measurement results can be saved and assigned to vehicles or customers.

  This can be helpful for workshop documentation, customer consultations, and test reports.https://www.autotestgeraete.de/produktkatalog/unterkategorien/bremsenentlueftungsgeraete/

• What should you do if the brake fluid needs to be changed?

  If a fluid change is necessary, the specified brake fluid should be used, and the system should be flushed or bled according to the recommended workshop procedure.

  Professional brake bleeding units and compatible brake bleeding adapters are available for this purpose.

  You can find additional solutions under Test and Service Equipment for Brake Systems.