My son was drivining his 73 mav a few days ago and lost all brakes. Fortunately he was able to get to the side of the road. This car has manual front disk and rear drum. The factory valve for the drums was left in when the disk convertion was done. The rear soft hose is what failed. The scarry part is he seemed to loos all breaking. When checking the master cylinder it appear the fluid loss was from the smaller section which would corrospond to the rear. Brake light did come on. I though he still should have had the front working but did not. Any ideas as to what might be wrong in the set-up?
Could be a number of things. But usually a disc brake master cylinder has a lager chamber for the front brakes, since the piston cavity is larger and requires more fluid compared to wheel cylinders. I myself have run a 73 with a drum master with front discs, but stopping power increased with the correct master.
With a catistrophic failure of a brake line the pedal will head straight to the floor. Rapid pumping will give you some brakes on the system that is intact and that will allow you to get the car pulled over and stopped. But it will not have any firmness left to the pedal that can allow driving safely on "one side" of the master. What can be done if stranded in the middle of nowhere? Cap off the bad line. On an old Bronco, I once used vise grips to cap the line after a brake hose was tore out on a tree root or something while offroading. I just cut the metal line, folded it over and pinched the fold tight with the vise grips (leaving it clamped of course). Braking still sucked but was OK to get out of the "boonies" and back to town.
Amen! I had to use mine once for an emergency stop. Unlike todays cars, mine will stop the car! I miss the hand brake that our cars have. It is much better than the foot pedal ones!
?? Thanks for the replys. I thought the reason for going to the two compartment/dual piston master was to prevent a complete failure. I guess I thought wrong.
Thats correct it is to prevent total failure, just because the pedal was low didnt mean you didnt have any stopping power.
Joe Based off what I know about brakes (not a lot) I would agree with you. If you are saying at the exact time of failure I would have had some braking I could not say as my son was driving and he stated he had none. But I can tell you this, I fill both sections up and tested it before repairing and i had nothing. Even when I pumped it I had nothing. After replacing the failed hose I had complete return of front and back. This total failure is what prompeted the original question. Maybe I can ask it in a better way is the factory proportional valvue tied together front to back? Should I have some braking and if yes what might have cause me to have no braking. Hope I am not confussing this. Thanks again for the responses
If you lose pressure in half the system the valve will move over to block the low pressure half. In theory that is. The brake warning lamp should come on and you should have some stopping power but the pedal will still go to the floor. Your stopping power will be at the end of travel but you should still have some braking. Not enough to drive it but enough to get you stopped eventually. The ebrake would be more effective. Most people panic and dont think of the ebrake. Its real easy to make suggestions in hindsight. Different story when your in panic mode. I've driven hundreds of cars with blown brake components etc. Your son would feel as he had no brakes even with the system doing its job and separating the system.
It seems even with old tecnology they could have made a better set-up that would have maintained most of the stoping power of the front or back. Add e braking pulling to your future training for the kids and grand kids.
If they made them that good -- too many morons would just keep driving on them broken -- until they had a bad accident and then they would sue the manufacturer for defective brakes. And the worst part is a jury would agree with the poor moron and they would win .......
I have experienced that complete loss of braking in that exact situation in my old Comet. My problem turned out to be an internally bypassing master cylinder. The brake light came on and I had no brakes at all, pedal went to the floor. I drove it(stuck in a horrible part of town) around I285 in rush hour using the parking brake and downshifting until I was close enough to home to call for help. My thought was: whatever happened to that dual circuit hydraulic system failsafe? I have often thought about that experience since I installed rear disc with the internal drum parking brakes(not sufficient for stopping a car in motion, they are design to hold it in place) so having a system that would actually allow some stopping power with one circuit down would definitely be a better idea. The master cylinder piston of the blown circuit should bottom mechanically against the front of the master cylinder bore or the other piston, giving some hydraulic pressure to the intact circuit, everything else working properly. Hypothetically, if you lose the front, you may almost reach the floor with the pedal before any pressure is achieved especially if the rear adjustment is a little loose, and, as someone mentioned already, you may have to pump the pedal to overcome any other slack in the system.
