Brake fluid absorbing moisture. Flush interval.


#1

Last week I put some additional ATE brake fluid into my reservoir. It came from a can I opened prob the better part of a year ago. I remember reading years ago that once you opened a can of brake fluid, it needed to be used up within some weeks because once opened, it’s shelf life was limited because it would be absorbing moisture. In the early days I dutifuly flushed my brake fluid every year.

Just like I changed my oil every other event.

But over the last few years I’ve gotten less serious about changing fluids. I’ve re-used oil that had to come out the engine for one reason or another, and I’ve re-used brake fluid that I’ve bled out of calipers.

Oil analysis showed me that my oil was just fine after half a season.

And now, brake fluid. Last week I bought a brake fluid tester. It checks the moisture content of the fluid. The brake fluid at the top of my reservoir, the several ounces that was recently poured out of the can opened a year ago, had so little moisture in it that it did not register on the tester.

I think I’m going to become less obsessed about changing brake fluid.

Next test will be to pull some brake fluid out of a caliper and see how it tests.


#2

You want to bleed the brakes every other event to remove the brake fluid that has been exposed to high temps. Other than that, new brake fluids … ATE, Girling LMA, etc… don’t really require a change. You get enough fresh from bleeding.