Just learned brake fluid absorbs water way faster than I thought

I was reading through a 2019 Bosch tech bulletin last night and it said brake fluid can absorb enough moisture in 18 months to drop its boiling point by 100 degrees. I've been telling people to flush every 2 years but honestly I've been pushing it to 3 or 4 on my own truck. Has anyone else seen corrosion inside calipers from old fluid?

2 comments

2 Comments

the_emery5d ago

Wait, is it really that fast? I used to think brake fluid lasted almost forever, like just top it off and you're good. But I saw some rusty gunk inside an old caliper on my buddy's project car last month that matched exactly what you're describing. The fluid came out looking like weak tea too, not even clear or amber like it should be. I flushed my own truck after that, and honestly I'm gonna stick to the 2 year rule from now on because that corrosion stuff is real nasty to clean out.

laura_allen5d ago

I mean yeah it absorbs moisture but I think people get a little too scared about it. Unless you're tracking the car or driving mountain passes fully loaded the boiling point drop usually isn't gonna matter in real world driving. I've pulled fluid out of 10 year old daily drivers that still looked fine and had no corrosion issues.