loganburns•17d agoMost Upvoted

Why does nobody talk about brake fluid absorbing moisture through the reservoir cap?

I was helping a buddy bleed his brakes on a 2010 F-150 last Saturday and we got to talking about how fast fluid goes bad. He pulled some old fluid from a sealed bottle that had been sitting in his garage for maybe 2 years and it was already darker than fresh stuff. That got me checking my own car and I found out that even the little vent hole in the cap can pull in enough humidity to drop the boiling point by like 50 degrees over a summer. I looked up some testing a shop in Phoenix did showing that fluid from a daily driver in a humid area can go from DOT 4 to barely DOT 3 levels in 18 months. Has anyone else measured their fluid age with a tester and been surprised?

2 comments

2 Comments

caseys3016d ago

I left a brand new bottle of DOT 4 in my trunk for 6 months and it tested worse than the 2-year-old stuff in my GMC. Arizona heat cooks everything.

claire6416d ago

Curious why you tested a sealed bottle you hadn't even opened yet? Sealed brake fluid shouldn't absorb moisture unless the cap was loose or the bottle was damaged.