Missing Brake Fluid

[AHartz]

I just got my car out of winter storage. For the second year, the brake pedal goes all the way to the floor with no resistance. Last year, there was (a lot of) evidence of brake fluid below the master cylinder. I replaced the master cylinder, bled the brakes, and had no problems for the rest of the driving season.

This time when I got the car out of storage, I can't find any evidence of leaking brake fluid - nothing under the master cylinder, no evidence at each caliper, each fitting, etc. The reservoir in the master cylinder was empty. I bled the brakes and was able to re-establish a firm pedal, but I still can't find any leaks with the system refilled.

I wish I would have thought enough to look at the floor where the car was stored to get an idea of where the leak was occurring (I was a little embarrassed when I left the place because I almost wiped out a row of other cars in storage - fortunately I grabbed the emergency brake lever in time!).

Any ideas of where the "missing" fluid could be going? Perhaps inside the vacuum booster? Does brake fluid evaporate which makes it difficult to locate a leak after a few months?

Adrian
'81 911SC

[tonythetarga]

It could be going into the booster. One way to check is to firm the pedal up and hold that pressure on. If the pedal starts to travel after a minute or so, fluid is going somewhere. If it isn't on the ground it might be dumping into the booster.

[Rouxzy]

Adrian,
If your booster is gone, (rarely do they go), let me know because I have a spare I can send your way at a good price. The new ones are over $600.00. Ouch!
Tom