Today I came very close to wrecking my car. Lost all of my brakes. When I checked the (dual) master cylinder, the front was still full, and rear was completely empty. When I went back to where it was parked all night, there was a big puddle of brake fluid under left rear wheel. I still can't tell where it was coming from by examining the car, but there is lots of fluid on wheel cylinder.

I have a new wheel cylinder for the front that I never used. Does the rear use the same one? Also, I thought the purpose of the dual cylinder was to prevent complete loss of brakes if either the front or rear fail? My pedal went right to the floor.

I was very lucky it was early Saturday morning and there was no one in front of me, or coming through the intersection when I had to blow right through a stop sign

I thought the purpose of the dual cylinder was to prevent complete loss of brakes if either the front or rear fail? My pedal went right to the floor.


That's my understanding - you may have had to pump the brakes, though. One of the first things I do on any old car is replace the brake system - lines and cylinders. I did the same thing as you in an old beetle once, that was enough.

I'd check your lines for corrosion and make sure you have the right proportioning valve installed. I'm not 100% on how everything is supposed to tie together for the front/rear and still work if you lose one, but it's certainly worth looking into why yours may not have worked correctly.

No idea if they are the same cylinders or not - I'm sure someone here can help with that.

I had that happen many years ago with my single reservoir master cylinder and the pedal hit the floor while I was approaching a red-light at an intersection. I must have had great presence of mind that day because I immediately grabbed the parking brake release with my left hand and then used the parking brake to stop my car the rest of the way home. Recently I went through the brakes on my 66 and thought everything was done util one of the original rear lines sprung a leak. Apparently this line was clogged for a long time and wound up rotting from the inside out.

The new wheel cylinder I had for the front didn't work in the back. Bought a new one, and all is well for now. Just need to bleed and adjust the brakes a little better tomorrow. I'll probably get new lines and new cylinder for the right side also.

"A chain is only as strong as it's weakest link"

Glad to hear you did not have a wreck. I'd replace all instead of one. Usually they all rust and deteriorate at the same rate.

I know that's not what you want to hear but please be safe.

jim