2016 OWNERS MANUAL / 0397
According to DOT and OEM requirements, brand new DOT 3
brake fluid must have a dry (no moisture) boiling point of at least
401
o
F/205
o
C, and a wet (moisture saturated) boiling point of no less
than 284
o
F/140
o
C. (Most far exceed these requirements, fresh out of
the bottle.) Older brake fluid (about 18 months) with even three per-
cent (3%) moisture content lowers the boiling point to 293
o
F/145
o
C,
which is dangerously close to the minimum standard requirements.
Water contamination increases the danger of brake failure because
vapor pockets can form if the fluid gets too hot. Vapor displaces flu-
id and is compressible, so when the brakes are applied, the actuator
may completely compress without applying the brakes!
In addition, water laden brake fluid promotes corrosion and pitting
in caliper pistons and bores, wheel cylinders, master cylinders, steel
brake lines and reverse solenoids.
Consumers must use only DOT 3—preferred—or DOT 4 brake fluid. DO
NOT USE DOT 5 BRAKE FLUID. DOT 5 FLUID WILL DAMAGE THE SEALS
IN THE ACTUATOR AND CALIPERS, CAUSING FAILURE OF BRAKES
THAT COULD LEAD TO INJURY OR DEATH. Any other type may not pro-
vide sufficient chemistry to protect against overheating. Brake fluid
should be completely replaced during annual (at least once every 12
months or more often if the system has shown evidence of brake fluid
loss) maintenance. Brake fluid types should never be mixed. Failure
to provide required maintenance can cause brake failure, leading to
incidents that result in serious injury or even death.
DOT 5 brake fluid is a silicone-based fluid and requires specific
materials for the boots, seals and wipers in the actuator master
cylinder and caliper. Those materials are NOT used in MasterCraft
trailers. Regardless of marketing claims made regarding a sup-
posed superiority of DOT 5 brake fluid, the fact is that it will cause
significant failure in the trailer’s brakes because it is not designed to
use DOT 5 brake fluid.
“Unexplained” brake failures are often traced to dragging brakes
caused by the E-stop cable being tripped or the use of DOT 5 brake
fluid. The underlying cause most often is because the brakes got
over-heated and caused the fluid to boil. This can occur when the
fluid level is appropriate, the linings are within specifications, and
the hydraulics appear to work properly.
DO NOT USE DOT 5 brake fluid in any component of MasterCraft
trailers. The silicone causes seals to swell and can bind up caliper
pistons. Do not use this in individual actuators, disc brakes or
solenoids.
The silicone in DOT 5 brake fluid also causes foaming bubbles when
forced through small orifices under high pressure, such as the
solenoid valves in a disc brake system. Bubbles in brake fluid result
in spongy brakes. Silicone also tends to become slightly compress-
ible at temperatures near its boiling point, which makes it generally
inappropriate for trailers used in mountain conditions.
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