Brake fluid boiling point surprised me after a 200 mile descent near Asheville

I always thought brake fluid was just brake fluid until last month. Took a Ford F-250 down the Blue Ridge Parkway with a loaded trailer, and by the time we hit the bottom the pedal went straight to the floor. Checked the fluid and it was dark brown, not the amber color it should be. Turns out DOT 3 absorbs water over time and that drops the boiling point from 400 degrees to under 300. Moisture test strips are $10 at Napa, worth picking up if you do any mountain work. Anyone else ever cooked their brakes on a long grade and blamed the pads when it was really the fluid?

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1 Comment

ross.kim6d ago

Check the brake fluid regularly or just flush it every couple years on any truck that tows, that dark brown color is a dead giveaway it's been soaking up moisture for way too long. Did you happen to check the fluid level before you left, or was it full and you still lost the pedal halfway down? That makes a big difference in figuring out if the fluid was old or if you've got a bigger issue like a soft line bulging under pressure.