Why convert to a dual master cylinder?
The single master cylinder that the 64-66 Mustang is originally equipped with provides fluid pressure to all four wheels at the same time. All four wheels are linked together in a hydraulic fluid circuit. If a problem develops in any of the four brakes, lines, hoses or single master cylinder, that creates a fluid pressure loss. This will cause you to lose both front and rear brakes.
With a dual master cylinder, the brakes are split front and rear. If a problem develops in the front, only the front brakes would be lost. You would still have the rear brakes to bring you to a stop. The same would happen if you had a problem with the rear brakes, you would still have the front brakes to bring you to a stop.
On a dual master cylinder, because it's a dual piston design, a problem within the master cylinder would only effect the front or rear brakes if one of the pistons failed. Of course, it is also possible that the master cylinder could fail completely and cause a total loss of braking, just as it could in any other car.
A sign that a master cylinder is failing is a spongy feeling pedal or a lower than usual pedal with no fluid loss when checking the fluid level. As with any car, if the brakes feel different than usual, check the fluid level immediately. Don't take a chance driving the car until you are sure all is well.
You can use the parking brake to stop the car if you lose all other braking, but it WILL NOT stop the car well at all! If you pull it on all at once, the rear brakes will lock and spin the vehicle around. The handle will stay pulled out because of the parking brake latch and will keep the parking brake applied.
1. The rear reservoir is for the front brakes. (This allows full pressure to the front brakes for proper brake balance.)
2. The front reservoir is for the rear brakes.
3. You must re-use the 64-66 pushrod on the new master cylinder. It is longer then the rod that comes with the 67 style dual master cylinder. If the 67 pushrod is used, a low brake pedal condition will exist.
4. The brass distribution block is used only for splitting the fluid to the left and right front brakes.
5. Remove the rear brake line from the brass distribution block.
6. The brass plug is for plugging the hole in the brass distribution block where the rear line was originally.
7. The first short line and union in the kit is to hook the rear line to the front reservoir.
8. The other short line in the kit goes from the rear reservoir to the brass distribution block.
Please note: Due to manufacturing variations on the 64-66 cars and the new master cylinder, adapter fittings may be needed for the lines and fittings. These adapters would be available at major auto parts stores such as NAPA.
* Please be advised that this information is for suggestion only and is based on prior experience. We at CJ Pony Parts can not be held responsible or liable for any mistakes or injuries connected with the topics covered.