06/02/2003
It can be a rather alarming experience when your parking brake, also known as the handbrake or e-brake, decides to give up the ghost. The symptoms you've described – a burning smell, sluggishness, and a caliper sticking – point towards a few common culprits. Understanding why your parking brake isn't engaging or is behaving erratically is the first step to getting it sorted. Let's delve into the most frequent reasons why your parking brake might not be working as it should.
The Role of Your Parking Brake
Before we explore the problems, it's useful to understand what your parking brake actually does. Unlike your primary braking system, which uses hydraulic pressure to force brake pads against the discs (rotors), the parking brake is typically a mechanical system. It's designed to hold your vehicle stationary when parked, especially on inclines, and can also serve as an emergency brake if your main hydraulic system fails. Many modern vehicles use a cable system that actuates the rear brakes, either by a separate set of shoes within the rear drum or by mechanically engaging the rear brake calipers.
Common Causes for Parking Brake Failure
The issues you're experiencing, particularly the sticking caliper and burning smell, strongly suggest problems with the rear braking system, which is where the parking brake usually operates. Here are the most common reasons:
1. Worn or Damaged Parking Brake Cables
The cables are the backbone of the mechanical parking brake system. They run from the handbrake lever inside the car to the braking mechanism at the rear wheels. Over time, these cables can stretch, corrode, or become stiff due to exposure to the elements. If a cable is binding, it might not fully release the brake, leading to drag, overheating, and that tell-tale burning smell. Conversely, if a cable has stretched too much or is damaged, it might not have enough tension to engage the brake effectively.
2. Sticking Calipers or Wheel Cylinders
This is a very likely cause given your symptoms. The caliper is responsible for squeezing the brake pads against the rotor. If the caliper piston or the mechanism that the parking brake cable actuates within the caliper becomes seized or sticky, it can cause the brake to remain partially applied. This is what appears to be happening with your front right brake. The burning smell is a direct result of the brake pad constantly rubbing against the rotor, generating excessive heat. The metal-on-metal contact and the subsequent heat can also cause the rotor to warp.
In vehicles with drum brakes at the rear, a similar issue can occur with the wheel cylinder, which forces the brake shoes outwards. Corrosion or dirt can cause the piston within the wheel cylinder to stick, leading to the brake dragging.
3. Issues with the Parking Brake Mechanism (Internal to Caliper/Drum)
Many parking brake systems incorporate a small mechanism within the caliper or drum brake assembly that allows the parking brake cable to apply force independently of the main hydraulic brake system. This mechanism can become corroded, gummed up with brake dust, or the internal spring can break. When this happens, the mechanism might not retract properly, causing the brake to stay engaged even when the handbrake is released. The need to strike the caliper suggests a mechanical binding issue.
4. Worn Brake Pads or Shoes
While less likely to cause a complete failure to engage, severely worn brake pads or shoes can reduce the effectiveness of your parking brake. If the brake pads are worn down to their backing plates, or if the brake shoes are worn thin, there might not be enough material left to create sufficient friction when the parking brake is applied.
5. Parking Brake Lever or Pedal Issues
The lever inside the car or the pedal can also be a source of problems. The mechanism that engages the cables might be worn, loose, or damaged. If the lever or pedal feels unusually loose or doesn't offer the expected resistance, it could indicate a problem with the linkage or the ratchet mechanism that holds it in place.
6. Contamination of Brake Components
Brake fluid leaks or the ingress of water and dirt into the braking system can lead to corrosion and contamination of brake components, including the caliper pistons, brake lines, and the parking brake mechanism itself. This contamination can cause parts to seize or operate inefficiently.
Diagnosing the Problem
Given that you've identified a specific wheel that's sticking, the diagnosis is more targeted. The burning smell and the need to physically free the caliper strongly point to a seized caliper or a problem with the parking brake actuation mechanism within that caliper.
Steps to Investigate:
- Visual Inspection: With the vehicle safely on jack stands and the parking brake released, try to spin the wheel by hand. If it's stiff or doesn't spin freely, the brake is likely dragging. Check the caliper for any signs of fluid leaks or damage.
- Check Cables: While it's harder to inspect the entire length of the cable, you can check where it connects to the caliper or brake assembly. Look for any obvious signs of corrosion, fraying, or binding.
- Caliber Functionality: The most probable cause is a sticking caliper. This could be due to a seized piston, corroded slider pins (though these usually affect the main brake), or the internal parking brake mechanism within the caliper.
Potential Repairs
The repair will depend on the exact cause. If it's a cable issue, the cable(s) will need to be replaced. If a caliper is sticking, it might need to be rebuilt or, more commonly, replaced. It's also possible that the entire rear brake assembly (pads, rotors, and caliper) on that side may need attention due to the heat damage caused by the constant dragging.
Here's a breakdown of common repair scenarios:
| Problem Identified | Likely Repair | Considerations |
|---|---|---|
| Sticking Caliper Piston/Mechanism | Replace caliper; rebuild if possible. | Often requires replacement for reliability. Ensure new caliper is compatible with parking brake function. |
| Binding Parking Brake Cable | Replace affected cable(s). | May need to replace both rear cables for even wear and performance. |
| Worn Brake Pads/Shoes | Replace brake pads/shoes. | Inspect rotors for damage from worn pads. |
| Corroded Rotor/Drum | Resurface or replace rotor/drum. | Severe heat damage may necessitate replacement. |
Can You Drive With a Faulty Parking Brake?
Driving with a dragging parking brake is not advisable. The constant friction generates excessive heat, which can severely damage your brake pads, rotors, and even the caliper or wheel cylinder. This overheating can lead to brake fade (reduced braking performance) and, in extreme cases, complete brake failure. The burning smell is a clear warning sign that something is seriously wrong. Additionally, a dragging brake increases fuel consumption and puts unnecessary strain on your drivetrain.
Frequently Asked Questions (FAQs)
Q1: Why does my parking brake smell like burning?
A: The burning smell is usually caused by the brake pads constantly rubbing against the rotor due to a sticking caliper, binding cable, or an improperly released parking brake mechanism. This friction generates extreme heat, causing the smell.
Q2: Can a sticking caliper cause my car to pull to one side?
A: Yes, a sticking caliper will cause that wheel's brake to remain partially applied, creating drag. This drag will make the vehicle pull towards the side with the sticking brake.
Q3: How much does it cost to fix a parking brake?
A: The cost can vary significantly depending on the cause and your location. Replacing a parking brake cable might range from £100-£250, while replacing a caliper could be anywhere from £200-£500 or more, including labour and parts. It's always best to get a quote from a qualified mechanic.
Q4: Should I replace both parking brake cables?
A: It's often recommended to replace both rear parking brake cables at the same time. This ensures even tension and braking force on both wheels, preventing premature wear on the new cable and maintaining balanced performance.
Q5: What happens if I ignore a dragging parking brake?
A: Ignoring a dragging parking brake can lead to severe damage to your braking system, including warped rotors, worn-out pads, damaged calipers, and potential failure of the parking brake system entirely. It also poses a safety risk due to compromised braking performance.
In summary, the symptoms you're experiencing are serious and require prompt attention. The most likely cause is a mechanical issue with the caliper or the parking brake mechanism at the front right wheel. Get it checked by a professional mechanic as soon as possible to ensure your safety and prevent further, more costly damage.
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