Ford Escort/Lynx 1981-1990 Repair Guide

Brake Master Cylinder


The brake master cylinder reservoir is located under the hood, attached to the firewall on the drivers side of the engine compartment.


BRAKE FLUID EATS PAINT. Take great care not to splash or spill brake fluid on painted surfaces. Should you spill a small amount on the car's finish, don't panic, just flush the area with plenty of water.

When adding fluid to the system, ONLY use fresh DOT 3 brake fluid from a sealed container. DOT 3 brake fluid will absorb moisture when it is exposed to the atmosphere, which will lower its boiling point. A container that has been opened once, closed and placed on a shelf will allow enough moisture to enter over time to contaminate the fluid within. If your brake fluid is contaminated with water, you could boil the brake fluid under hard braking conditions and lose all or some braking ability. Don't take the risk, buy fresh brake fluid whenever you must add to the system.


See Figures 1 and 2

  1. Before removing the master cylinder reservoir cap, make sure the vehicle is positioned on a level surface.
  3. Wipe clean the cover and the area around the master cylinder, before opening it up. When satisfied nothing will contaminate the fluid, then open the master cylinder to inspect the fluid.
  5. On early model vehicles without translucent (see through) reservoirs, open the master cylinder cover by prying the retaining clip off to the side and remove the master cylinder cover.
  7. If the level of the brake fluid is within 1 / 4 in. (6mm) of the top, the fluid level is OK. If the level is less than half the volume of the reservoir, check the brake system for leaks. Leaks in the brake system most commonly occur at the wheel cylinders or at the front calipers. Leaks at brake lines or the master cylinder can also be cause brake fluid loss.

There is a rubber diaphragm at the top of the master cylinder cap. As the fluid level lowers due to normal brake shoe wear or leakage, the diaphragm takes up the space. This is to prevent the loss of brake fluid from the vented cap and to help stop contamination by dirt.

  1. After filling the master cylinder to the proper level with brake fluid (Type DOT 3), but before replacing the cap, fold the rubber diaphragm up into the cap, then replace the cap on the reservoir and snap the retaining clip back in place.
  3. On later model vehicles with the translucent master cylinder reservoir, check the brake fluid by visually inspecting the fluid level against the level markings on its side.
  5. the fluid level should be between the MIN and the MAX level marks embossed on the side of the reservoir. If the level is low, remove the reservoir cap and fill to the MAX level with DOT 3 brake fluid.
  7. When the fluid is at the correct level, replace the reservoir cap.

The fluid level will decrease with accumulated mileage. This is a normal condition associated with the wear of the disc brake linings. If the fluid is excessively low, have the brake system checked.

To avoid the possibility of brake failure that could result in property damage or personal injury, do not allow the master cylinder to run dry. Never reuse brake fluid that has been drained from the hydraulic system or fluid that has been allowed to stand in an open container for an extended period of time.

Click image to see an enlarged view

Fig. Fig. 1: The brake fluid level should be checked periodically by looking at it through the translucent reservoir (on cars so equipped)-1988 Escort shown

Click image to see an enlarged view

Fig. Fig. 2: Add brake fluid through the reservoir filler after wiping possible contaminants away with a clean cloth