MC Leaking?

halifaxhops said

I would take the vacuum line off the power booster and look for fluid before you get a master. It could be sucking the fluid out of the back of the master.

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Unlikely in our cars. The gap between the MC and booster is open to the air, w/ just a dust filter. You are thinking of newer cars w/ flat pancake boosters. They don't have the inner belllows of ours and must seal vacuum between the MC & booster. My 85 M-B is like that, and I think my minivans.

I would first suspect fluid is slopping out the reservoir cover. A little detective work will resolve. Wipe it clean and see if you get any drops while sitting, or only when driving. Tape paper towels above the ports and see if they get wet. If so, the leak is from the cover.

You don't have to bleed the whole system when changing the MC. If you get all air bubbles out of the MC and can still see fluid in the tubes, you can just connect them and have solid fluid. Perhaps have a helper just barely press on the brake pedal as you tighten the fittings, flowing a little fluid out (catch w/ newspapers, it will remove paint). Still, you should refresh the fluid every 3 yrs or so to avoid internal rust, unless using silicone fluid (like me).