Your Ford Thunderbird's brake booster is built to multiply the force you apply to the brake pedal, causing the car to stop or slow down. It does so effectively using an internal diaphragm, which may get punctures and other mechanical failures after years of service. Here are some of the common problems encountered on Ford Thunderbird brake booster:
A heavy pedal may likely be the result of vacuum or fluid leaking from the booster. To check if your car's brake booster is leaking, inspect the pistons, valves, and hoses for signs of wear and damage. Since the internal diaphragm, which provides the vacuum for the brake, may harden over time, it's important that you also inspect it for punctures and other damage.
Another possible cause of a heavy pedal is car vacuum damage. Verify if your car vacuum is damaged by holding the brake pedal down then starting the engine. The brake pedal should pull down slightly when the engine is started. If this doesn't happen, then the vacuum needed by your car is insufficient. Use a vacuum gauge to check for adequate vacuum. The booster should have a vacuum level of around 16-20 inches.
The brake booster is connected to the rear of the master cylinder using a pin. This pin shoves the interior valve open in the brake booster. If the length of the pin is inappropriate for the booster, either too short or too long, then the valve will not open at the exact time needed. Due to this malfunction, the pressure required to stop the vehicle is not activated, and it takes a longer distance for your brake to stop the car.
As part of your vehicle's power braking system, a broken booster can create a significant amount of noise when you step on the brakes. This is most likely caused by a hole or other problems with the vacuum line attached to the brake booster. Air is forced through the holes in the vacuum line, producing the hissing or whining noise you hear when you brake.