Likely Causes:
* Low Brake Fluid: This is the most common and easiest to check. The brake fluid level should be visible in the master cylinder reservoir (usually a clear or translucent container). If it's low, you have a leak somewhere in the system – this is a serious safety issue and needs immediate attention. Do not drive the car until this is addressed.
* Leaking Wheel Cylinder(s) or Caliper(s): Brake fluid leaks are usually visible as wet spots on wheels, brake lines, or under the car. Wheel cylinders (on drum brakes, if your Mark VII has those on the rear) and calipers (on disc brakes, likely front and possibly rear) can leak, causing low brake fluid and hard, spongy, or failing brakes.
* Leaking Master Cylinder: The master cylinder is the heart of the system; if it leaks internally or externally, it will result in low fluid and poor braking.
* Brake Booster Failure: The booster uses engine vacuum to assist in braking. If it fails, you'll need significantly more force on the pedal to stop. A running brake pump (meaning the pump is cycling rapidly) often indicates a booster problem. This is especially likely given the hard pedal.
* Air in the Brake Lines: Air in the lines can cause a spongy or hard pedal, but the constantly running brake pump makes this less likely as the main issue. Air would usually be expelled during normal braking.
* Restricted Brake Lines or Hoses: Clogged or kinked brake lines prevent proper fluid flow. This is less likely to cause a constantly running pump though.
* Faulty Proportioning Valve (if equipped): This valve regulates braking pressure between the front and rear wheels. A malfunction can cause uneven braking or a hard pedal.
What to Do:
1. Safety First: Do not drive the car until the problem is diagnosed and fixed. Driving with low brake fluid and a failing system is extremely dangerous.
2. Check the Brake Fluid Level: This is the quickest and easiest check. If it's low, locate the leak immediately.
3. Inspect for Leaks: Carefully examine all brake lines, hoses, wheel cylinders, calipers, and the master cylinder for any signs of leakage (wet spots, fluid drips).
4. Professional Help: Unless you have significant experience working on brake systems, take your car to a qualified mechanic immediately. Brake repair is crucial for safety, and improperly repaired brakes can lead to serious accidents. The constantly running pump strongly suggests you need professional diagnosis and repair.
Don't attempt to troubleshoot or repair the braking system yourself unless you are a trained mechanic. Your safety and the safety of others depends on properly functioning brakes.
