See Figures 1 and 2
The recommended maintenance interval for checking the fluid level in the master cylinder is six months or 6,000 miles. On 1965-1966 models, unscrew the filler cap and diaphragm which seals the master cylinder. Fill the reservoir to 3 / 8 inch from the top and install the filler cap, making sure that the diaphragm is properly seated in the cap. On 1967 and later models with dual master cylinders, push the retaining clip to one side and remove the filler cap and diaphragm. Fill the reservoir to 1 / 4 inch from the top and install the cap and diaphragm. If factory-recommended, high-temperature, heavy duty brake fluid is not available, top up with fluid of DOT 3 quality or better, for both drum and disc brake applications.