I had the check brake light flash on my car Sunday night. I checked the master cylinder, and brake fluid was a 2 part mix, almost like oil and water. You can clearly make out a clear skin layer over what is a very smokey looking brake fluid.

There is also brake fluid with the consistency of toothpaste at the top of the cylinder and around the rubber boot.

My question is...How the Ferk does so much moisture get into the braking system??

Brake Fluid is hydroscopic so it picks up water everywhere - even when it's say sitting in the drum waiting to be used at the workshop or if there's a poorly sealing master reservoir cap. When it gets 'wet' the boiling point substantially reduces and all sorts of drastic things happen.

After doing a lot of driving in mountainous terrain, you make it a habit to replace it and bleed brakes annually.

When it gets hot, like all things, it expands, that's why there is vents in your master cylinder cap, when it cools, it draws in air, and with the humid weather we have been having, a lot of moisture.

Change it often, and use dot 5 fluid, it has a much higher boiling point when wet than the stock stuff, Castrol is good, expensive, but good.

Get that one to service dept soon... and I would be reluctant to drive it there!