Not a big deal, but has occured 3 times. After having the kitty in the air on a 4 post lift working on various things. When I lower it and go to back out of the bay slowly, when I first apply brakes to stop, the pedal goes all the way to the floor with no feeling of stopping. The "flinch" is to quickly reapply and the brakes are back and fine. No other time(s) does/has this occured.

Anyone have an answer how or why this would happen?

 

Just to be sure: you had the engine off (at least some of the time) while it was in the air?

I'm thinking it relates to (loss of) vacuum, but that would be most unlikely if engine running all the time.

 

The only time I experienced this was after I did a lot of brake work and had an air bubble in the brakes.

If all is working fine now, then I would be questioning the check valve in the brake booster line. That would be the most likely suspect.

 

Yes, car was off and not running. Doing fluid changes, rear front stabilizer bars, front A frame (ball joint one).. Car can sit parked for days and it NEVER occurs. Just when it's been in the air for some time. Like rotating tires it was fine, even though it was in the air, but only like 30-40 minutes.

 

Or when I had the CV replaced by a shop, it didn't happen.

 

Kinda makes me wonder if you have a brake line that is a little tight and when you keep it on the lift for a long time, it tugs on the line and allows a bit of air to seep in. I would think that you would be able to spot atleast a few drops of brake fluid on the rim/ground under the point of interest.

 

No fluid anywhere except the one that developed after all the fluid changes. About 18-20 inches back from front passenger bumper, about 1 foot towards driver's side from passenger wheel. Looks like oil, took 9 months to drop 1/2 quart on dipstick.

Think perhaps using 15,000 mile synthetic might be the cause. As that's when it started, not a drop before the oil change.

 

Dell, sounds like you have an interesting quirk on your hands. Not sure where to take this one at the moment.