Odd unknown brake fluid leak
Anyone had a brake fluid going low yet no sign of a brake fluid leak anywhere? Any ideas where it could be going? 2008 Cobalt LT. Wife said brake fluid light came on. Checked reservoir and it was indeed very low. I refilled it. Pressed the brakes and held. Pressure was good. No noises or signs of leaking. Then a couple months down the road and same thing happened. Checked reservoir and fluid almost gone again. At this point I assumed it was a rear brake drum wheel cylinder leaking slowly. I disassembled both brake drums to find both cylinders perfect and not leaking (I had already replaced one of them a couple years prior). Boots good. No leaks at all and no signs of previous leaks or any fluid at all. Traced brake lines, all in perfect condition. Checked connections at front calipers etc. All perfect. Any ideas where the fluid is going that is leaving no sign of a leak at all?