KINGBOLEN Brake Fluid Liquid Tester Pen

KINGBOLEN Brake Fluid Tester — pen-style brake fluid moisture tester with 5 LED indicators, calibrated for DOT3 and DOT4 brake fluid.

• Quickly test brake fluid quality and moisture content to know when fluid replacement is needed.
• 5 LED indicators show water percentage with green / yellow / red status lights.
• Calibrated for DOT3 and DOT4 brake fluids (DOT4 is used in most cars produced since 2006).
• Results in seconds — simple one-button operation.
• Protective cap included; CE and RoHS approved.
• Powered by 1 × AAA / 1.5V battery (not included); auto power-off after about 12 seconds of inactivity.

How to use:

Press the top button to turn on — a green light should light up (if not, replace the battery). Unscrew the vehicle brake fluid reservoir lid and remove the tester cap. Dip the probes into the fluid; LEDs show moisture percentage. After testing, reseal the reservoir tightly.

LED reading guide

Green: no water. Green/Yellow: less than 1% water. Green/Yellow/Yellow: about 2% water. Green/Yellow/Yellow/Red: about 3% (replace recommended). Green/Yellow/Yellow/Red/Red: about 4% (replace urgently).

Why test brake fluid?

 Brake fluid absorbs moisture from the air over time. Higher water content lowers boiling point and can reduce braking performance. Regular checks help prevent brake-related safety issues.

Care tips: Wash the probe with tap water after every use. Avoid prolonged exposure of brake fluid to air. If fluid contacts skin or clothing, wash thoroughly with water.