Magically disappearing brake fluid in 2008 Pontiac Vibe

[mmeiser]

New user. Have had my 2008 Pontiac Vibe with manual transmission since about 70,000 miles, now at 230,000 miles.

I am loosing about an ounce of Dot 3 fluid a day whether I drive it or not. I am through about a bottle of brake fluid over the last few weeks. Driving / not driving does not seem to change a thing. I cannot find drips anywhere. Car sits for days. Still looses fluid. Nothing on the ground.

Things I have inspected working backward from the most recent.

• Power Brake booster... dry as a bone, I really thought this was going to be it!

• vacuum line to the power brake booster dry not any trace of it escaping back into the engine

• nothing around the ABS module, can see every inch of line back and forth around the engine compartment

• the hydraulic clutch, not a drop of fluid under the boot, no leakage around any lines can see 100% of lines from the master cylinder

• all four brakes, disc front, drum rear, checked every boot dry, every bleed nipple, everything

• flex lines in the wheel wells

• every brake line I could see and even where I couldn't see I looked for fluid pooling on a pan or flashing

The thing is you would think driving it would make it worse due pressure. Everything downstream from the power brake booster would be under extreme pressure. Indeed I tried pumping the brake in the car for prolonged periods of time no detectible change in fluid level.

I have checked every place I can and it's driving me nuts. At least it does not seem to be getting worse.

Some background. About six months ago I replaced the two original equipment disc brake calipers and right size flex hose as my right caliper was starting to stick. The calipers were NOT the issue. It was the master cylinder, probably a bad o-ring or just dirt. Cause 230,000 miles. I still have it because I intended to disassemble it to satisfy my curiosity. Still may. For six months after this work not a drop of fluid lost. Everything perfect. Then a brake light a few weeks back. Brake fluid was not to the level of safety concern just at the sensor. Never lost any function. Topped it off, but I noticed after driving it the fluid was low again so I started checking everywhere I park every time I park. Nothing anywhere. I figured it was burning it but it continues to drop even when I haven't driven it for days. You cannot burn dot fluid while the car is sitting still. Indeed as mentioned I have checked the power brake booster vacuum line and found no fluid in that or the booster. Not even any residue.

I have checked other fluid levels like oil, power steering. Not the manual transmission, cause that has no dipstick though there is a clear window somewhere to see fluid level. I will find that and check. The thing is i don't think the brake system is connected to any other engine functions. I.E. even the hydraulic clutch piston is external to the engine and transmission and clearly visible. There is no way for fluid to travel into the clutch housing or transmission.

All this and yet somewhere I have lost almost a bottle of brake fluid over the last few weeks.

So what am I missing!?

[mmeiser]

Well, After six days this oost has not been approved by a moderator, lol.

Was a great forum. I guess it is dead?

p.s. not that it matters but I found the leak. It was the clutch master cylinder. I was leaking to the inside behindthe caroet and I can only assume right into the frame because it never dripped on the ground nor pool under the floor mat. $22.99 part. Hours of work. Had to remove the master cylinder to get to it and the clutch pedal. Luckily not the dash. But my back is still sore from climbing up under the dash. Honestly I think I soent more time trying to figure out where it was leaking.