I got the fright of my life yesterday! I reversed my 1986 series 3 off my driveway and touched the brake pedal which just sank straight to the floor and the car carried on backwards heading for a car coming down the street. I pressed the pedal again and this time they were fine. I drove it off the driveway with no more problems and going along my quiet street tested the brakes a dozen times and they worked fine. 200 metres later at a junction the same thing happened! It takes a few seconds for your brain to figure out what to do by which time I was half way out of the junction and heading for the back of stationary traffic!!!!!! Handbrake just slowed it a little.I figured turning off the ignition won't stop it and I would loose pas to steer around cars or into a lamppost to stop! I slammed it into reverse which locked the rear wheels then put it into neutral. When no traffic was near I reversed back onto my street and crawled home! I have checked underneath and no leaks from brake pipes, fluid level in reservoir is unchanged no warning light from pressure differential unit. I understand how this could happen, I thought there was some kind of mechanical failsafe. Anybody had this problem? Thanks. I'm just going out to fit a spare master cylinder I have in my garage.

 

Replace the master cylinder do not drive the car..

 

Scary for sure.

There are lots of things that "SHOULD" happen, but sometimes mechanical devices just fail for no apparent reason, and not to some predetermined formula.

Just be thankful you were local and slow, albeit when that pedal hits the floor, for some reason the brain doubles the speed.

Take care.

 

Whew????


Agree with all of the above. I've driven many a critter with poor or almost no brakes. Once, my 57 Ford truck from the Wilshire corridor through Hollywood to our home in Granada Hills. Blown front brake hose. But, and a big one, it was equipped with a four speed including granny low.


More wrong in your car than you might know!! A prior failure? As a "modern" car, it is piped two and two. One part fails, two wheeled braking remains. So,a past fail on one, and now, the second failed, leaving zilch?


So, in addition to a suspect master, rear calipers?


The hand brake is minilmal even with good function. many, as mine are not.


Whew!!!


Carl

 

My bet is the master cylinder is leaking internally - was DOT 3 used in the system ? If it is the MC leaking you need to replace it.... use the proper brake fluid and bench bleed it prior to installation ..bleed all brakes..
If it were a caliper leak,.. the other end of the system would still work. If it were a beginning failure of the internal seals on the MC,.. no brakes will work First you will get spongy brake pedal,..then periodic failure and then complete brake failure as you just had.

 

When I was dirt poor, decades ago (college student), I drove a 73 Ford Maverick with leaky brake wheel cylinders. I used to top the master cylinder periodically. To stop, I had to prime the brakes by pumping a few times to build pressure. That was so stupid and utterly dangerous. But such were those days....

 

[/I]Hi, thanks to all who replied so quickly. I did change the master cylinder with a spare and all is working as it should. I have had approx 12 of the series 3 over the past 20 years or so, stripping down,restoring, repairing and driving them and have had every problem under the sun but never total brake failure! I just thought to ask you all in the hope you agreed as I was tight for time and didn't have the luxury of a leisurely fault tracing morning!