20/02/2006
A malfunctioning parking brake can be a significant safety concern, leaving you vulnerable to your vehicle rolling away, especially when parked on an incline. While modern vehicles often feature sophisticated electronic parking brakes (EPBs), many still rely on traditional mechanical cable systems. Understanding how your parking brake works and common reasons for its failure is the first step towards ensuring its proper function. If you're experiencing issues, it's always advisable to have the root cause remedied by a qualified workshop, but knowing the basics can empower you as a vehicle owner.
The primary function of a parking brake, often referred to as a handbrake or e-brake, is to keep your vehicle stationary when parked. It operates independently of your main hydraulic braking system, typically engaging the rear wheels. On older vehicles, this is usually achieved through a lever between the front seats, connected by cables to mechanisms within the rear brake drums or calipers. Newer systems might use a switch that activates an electric motor to apply the brakes.
Common Causes of Parking Brake Failure
Several factors can lead to a parking brake losing its effectiveness:
- Cable Stretch or Wear: Over time, the steel cables that connect the parking brake lever to the brake mechanism can stretch. This stretching means more lever travel is required to achieve full braking force. The outer casing of the cable can also fray or become damaged, hindering smooth operation.
- Corrosion: Exposure to the elements, particularly road salt and moisture, can cause corrosion in the cables, levers, and brake components. This corrosion can seize up moving parts, preventing them from operating correctly.
- Worn Brake Shoes or Pads: If your parking brake relies on separate brake shoes within the rear drums, these shoes can wear down over time, reducing their contact surface with the drum. Similarly, if the parking brake is integrated into the rear disc brake calipers, the pads can wear, requiring more adjustment.
- Sticking Calipers or Wheel Cylinders: The mechanisms that apply the brake shoes or pads can become stuck due to corrosion or lack of lubrication. This can prevent the brake from engaging fully or, conversely, cause it to drag even when released.
- Damaged Lever or Pedal Mechanism: The interior lever or pedal mechanism itself can suffer from wear or damage, affecting its ability to engage the cables properly.
- Electronic Parking Brake (EPB) Faults: For vehicles with EPBs, issues can stem from faulty actuators, sensors, control modules, or wiring problems. These systems are more complex and often require diagnostic tools to pinpoint the exact fault.
Troubleshooting and Basic Checks
While a workshop is the best place for a definitive fix, you can perform some basic checks:
- Lever/Pedal Travel: Observe how far you need to pull the lever or press the pedal before the brake engages and holds the vehicle. Excessive travel (e.g., the lever coming all the way up to the seat) is a strong indicator of stretched cables or worn components.
- Holding Power: On a safe, level surface, engage the parking brake firmly. Try to gently move the vehicle forward or backward. It should resist movement. Then, try it on a gentle incline (if safe to do so) and see if it holds the vehicle securely.
- Listen for Noises: When applying or releasing the parking brake, listen for any grinding, squeaking, or sticking sounds, which could indicate problems with the cables or brake mechanisms.
- Check for Dragging: After releasing the parking brake, if you notice a persistent noise or feel resistance when driving, the brake might be dragging, meaning it's not fully releasing. This can lead to increased fuel consumption and premature wear on brake components.
Proper Usage for Longevity
How you use your parking brake can impact its lifespan and effectiveness:
- Firm Application: Always apply the parking brake firmly without operating the release button. This ensures a secure hold. On a downhill or uphill slope, apply it as firmly as possible.
- Release Procedure: To release the parking brake, pull the lever up slightly to take the tension off the release button, press the release button, and then fully lower the lever. This prevents undue wear on the button and the locking mechanism.
- Regular Use: It's a good idea to use your parking brake regularly, even if you have an automatic transmission. This helps to keep the components from seizing due to lack of use and corrosion.
- Avoid Over-Reliance: While essential, avoid relying solely on the parking brake to hold a vehicle on very steep inclines for extended periods, especially if you suspect it's not in perfect working order. Engaging first gear (or 'Park' in an automatic) provides an additional layer of security.
When to Call the Professionals
The parking brake is a critical safety system. If you notice any of the following, it's time to book your vehicle into a reputable workshop:
- The parking brake does not hold the vehicle on even a slight incline.
- The lever or pedal requires excessive force to engage.
- The parking brake feels spongy or inconsistent.
- You hear unusual noises when applying or releasing the brake.
- The parking brake fails to release completely, causing the vehicle to drag.
- Warning lights related to the parking brake illuminate on your dashboard.
A workshop will typically perform the following:
- Inspect the parking brake cables for wear, damage, or corrosion.
- Check the condition of brake shoes or pads (depending on the system).
- Examine the parking brake mechanism at the wheels for proper operation and lubrication.
- Adjust the parking brake cables to ensure correct tension and travel.
- For EPBs, they will use diagnostic equipment to read fault codes and test the electronic components.
Parking Brake Adjustment: A Look Inside
The adjustment process for a mechanical parking brake typically involves tightening the cables. This is often done via an adjuster nut located either under the handbrake lever inside the cabin or at the point where the cables meet at the rear axle. The goal is to achieve the correct amount of free play in the lever or pedal before the brakes begin to engage.
A common specification might be that the parking brake lever should have 6-8 clicks before it starts to feel resistance, and it should hold the vehicle firmly when pulled up about two-thirds of the way. However, these specifications vary significantly between vehicle models, making a workshop manual or professional guidance essential.
Electronic Parking Brake (EPB) Considerations
EPBs offer convenience but introduce complexity. They typically consist of:
- A dashboard switch that activates the system.
- An electronic control unit (ECU) that manages the braking.
- Actuators, usually integrated into the rear brake calipers, that physically apply the brakes.
When an EPB fault occurs, it's rarely a simple cable adjustment. The ECU monitors the system for faults, and if an issue is detected (e.g., a faulty actuator motor or sensor), it will typically illuminate a warning light. Repairing an EPB often involves replacing faulty actuators, recalibrating the system using specialized software, or addressing wiring harness issues.
Table: Mechanical vs. Electronic Parking Brakes
| Feature | Mechanical Parking Brake | Electronic Parking Brake (EPB) |
|-----------------|------------------------------------------|-----------------------------------------------|
| Complexity | Relatively simple | More complex, involves electronics |
| Failure Mode| Cable stretch, corrosion, component wear | Electrical faults, actuator failure |
| Common Issues| Poor holding, excessive lever travel | System faults, warning lights |
Frequently Asked Questions
Q1: Can I adjust my parking brake myself?
A: For mechanical systems, yes, if you have the correct tools and a vehicle-specific manual. However, incorrect adjustment can be ineffective or cause brake drag. For EPBs, self-adjustment is generally not possible and requires diagnostic tools.
Q2: How often should the parking brake be checked?
A: It's good practice to have it inspected during regular vehicle servicing. You should also be aware of its performance during your regular driving.
Q3: My parking brake warning light is on, what should I do?
A: Do not ignore this warning. It indicates a fault within the parking brake system, whether mechanical or electronic. Have it diagnosed by a professional workshop immediately.
Q4: Does using the parking brake wear out my main brakes?
A: Not directly, but if the parking brake is dragging, it can cause premature wear on the rear brake components. Proper adjustment prevents this.
In conclusion, a properly functioning parking brake is a cornerstone of vehicle safety. While minor issues might be addressed with careful adjustment, more significant problems, especially those involving electronic systems, necessitate the expertise of a qualified mechanic. Regular checks and proper usage will help ensure your parking brake remains reliable, keeping you and others safe on the road.
If you want to read more articles similar to Parking Brake Fixes & Maintenance, you can visit the Repairs category.