Ford Pick-ups and Broncos 1987-1996 Repair Guide

Brake Master Cylinder



Use Ford Heavy-Duty Brake Fluid, Ford specification No. ESA-M6C25-A, or equivalent; do not overfill.


See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Add clean brake fluid to the brake master cylinder reservoir as necessary

The master cylinder reservoir is located under the hood, on the left side firewall. There is a rubber diaphragm in the top of the master cylinder cap. As the fluid level lowers in the reservoir due to normal brake shoe wear or leakage, the diaphragm takes up the space. This is to prevent the loss of brake fluid out the vented cap and contamination by dirt.

  1. Before removing the master cylinder reservoir cap, make sure the vehicle is resting on level ground and clean all dirt away from the top of the master cylinder.
  3. On early models, pry off the retaining clip or unscrew the hold-down bolt and remove the cap.
  5. On later models, simply unscrew the cap.
  7. The brake fluid level should be within 1 / 4 in. (6mm) of the top of the reservoir, on cast iron cylinders, or, at the level mark on plastic reservoirs.

If the level of the brake fluid is less than half the volume of the reservoir, it is advised that you check the brake system for leaks. Leaks in the hydraulic brake system most commonly occur at the wheel cylinder.

  1. After filling the master cylinder to the proper level with heavy duty brake fluid, but before replacing the cap, fold the rubber diaphragm up into the cap, then replace the cap in the reservoir and tighten the retaining bolt or snap the retaining clip into place.