View Full Version : Brake fluid evaporation

Dave Russell
05-02-2004, 02:06 AM
A question came up a while back about "does brake fluid evaporate?" At the time I was investigating but wasn't sure yet.

I have had an open beaker of Castrol GT LMA fluid sitting on the bench for the last six months. The level has not changed & the color is still crystal clear.

I stirred 20% water into another sample & of course the volume did increase but it did not decrease due to evaporation either. The color stayed clear.

Either it has taken on water while it evaporated to maintain the original level, or it doesn't absorb water & doesn't evaporate.

Not very scientific but maybe an indication. Or maybe it takes more than six months for something to happen.

05-02-2004, 03:18 AM
Hello Dave,
I don't know what prompted the original question, but if it related to fluid level dropping in a master cylinder reservoir, then I would say no, it does not evaporate.
Fluid level in a brake master cylinder reservoir on disc braked cars naturally drops as the pads wear. This may cause concern to some people, if they start looking for leaks and find none.

Just a thought,

Alec graemlins/thirsty.gif

Dave Russell
05-02-2004, 10:54 PM
It was this thread;