Sealey brake fluid tester boil test sealey vs0271 the approved method of testing the water content of brake fluid just 3 of moisture can lower the brake fluid boiling point by over 100 c the best way to detect this small water content is to measure the boiling point of the fluid the unit incorporates a heater element an lcd display and a power lead for use on 12volt dc power supplies works on dot 3 4 and 5 1 specification fluids supplied in carry case with full operating instructions