Brake fluid disappearing

[Sieg]

Off the PT topic but relates to ABS brake systems........

'05 Toyota Tundra pickup. Brakes have been trouble free since new. Still running stock rear drum shoes, replace front pads 6 months ago. Twice in the last two months the brake warning light has come on. Checked fluid in the reservoir the first time and it was close to minimum, visually checked the lines for leaks and refilled with 5.1 fluid.

A month later it comes on again, pull the rear drums and inspect wheel cylinders...dry, adjusted the shoes as I'd noticed the parking brake tension was questionable, check lines and junctions, no leaks.

Yesterday the light comes on again and the reservoir level is close to minimum. I go under the truck with a flashlight and check every brake/abs line, reservoir, rotor/drums for any sign of fluid both visual and with my hand. Couldn't find a trace of brake fluid on the vehicle, nor has there been any on my clean concrete driveway.

Vehicle has not had the sytem flushed so it is OEM fluid from Dec '94 build date. Filling with 5.1 which is supposedly compatible.

I'm close to stumped, it's like it is evaporating.

Anyone have a similar experience?

[Vegas69]

Leaking out the back of the master cylinder into the booster.

[Sieg]

Originally Posted by Vegas69

Leaking out the back of the master cylinder into the booster.

I don't exactly like what you're saying but that's my primary conclusion at this point. Is that a common occurrence?

[Vegas69]

I have no idear but it's easy to check. Unbolt the master and you should be able to pull it out a little and take a peak. I'd also pull the vaccum hose and take a look.

[Sieg]

Thanks for the input, I respect your knowledge and insight.

[elitecustombody]

I agree with Todd, it's a good possibility that's where the fluid is disappearing.