pacerdonfl

Gotta be leaking master cylinder into booster. It's slowly sucking down the 3rd full brake fluid reservoir and not a drop anywhere to be seen. Brakes are tight and all working fine.

I'm replacing master cylinder now...prolly have to replace booster soon since it must have a leak around the push rod.

spuds

Thats a tough call on the booster,lets see what folks with that experience have to say about it.Was it hard to do the MC?

I would leave it as its 130.00 for a rebuild at partsgeek and I dont have an extra 130 to spend 'just because'.

But thats me based on my financials.YMMV.

pacerdonfl

Just replaced the brake master cylinder - piston seal and booster area dry as a bone. No fluid anywhere under car or near firewall - ALL 4 WHEELS BRAKING SMOOTHLY AND FIRMLY - WHERE IS THE FLUID GOING????? ARRRRGHHHHH!

Superfast1

Did you prime the master cylinder before you installed it? It's a must to avoid bubbles in the line. Surf the net if you don't know how. It's very easy to do.

spuds

Is it still leaking? All thats left is lines or callipers. I have an idea,have someone manipulate the brakes while you search from start to finish,maybe something will show under pressure.
Another thought,clean all lines spotlessly clean,and look for leaks,also remove tires and look for leaks as someone steps on boosted brakes.

pacerdonfl

24 oz of brake fluid has gone somewhere in the last 3 weeks, and not a drop visible under the hood or car or on driveway. I'm 72 yrs old and have been doing my own brakes since my '61 Star Chief. Many cars and pickup trucks.

As I said - replace master cylinder, bled system, brakes are rock hard, grabbing evenly and slowing/stopping like new.

This is mystery. I'll keep looking.

spuds

Cool,look forward to hearing if the mystery fluid loss continues.Good luck.