Troubleshooting Trailer Brakes That Won’t Release: Common Causes and Solutions

[MikePhua]

Introduction to Trailer Brake Issues
One of the most common problems faced by heavy equipment owners and operators is malfunctioning trailer brakes. Specifically, when trailer brakes fail to release after use, it can cause numerous safety concerns, as well as potential damage to both the trailer and the vehicle towing it. A 20-ton tag trailer, designed to carry large and heavy loads, is especially sensitive to brake issues due to the sheer weight involved. Understanding why brakes might not release is crucial for both safety and the long-term health of your trailer.
Understanding How Trailer Brakes Work
Trailer brakes operate similarly to the braking systems found in most vehicles, but with the added complexity of having to work in tandem with a towing vehicle. Most heavy-duty trailers use either electric or hydraulic brakes, with air brakes being common on larger units. The brakes are typically activated when the towing vehicle slows down, transferring braking force to the trailer. When the vehicle comes to a stop, the brakes should release, allowing the trailer to roll freely.
However, there are several reasons why these brakes might fail to release as expected.
Common Causes for Trailer Brakes Not Releasing

1. Damaged or Faulty Brake Components
   One of the primary reasons brakes fail to release is when there are issues with the brake components themselves. In electric brake systems, the magnets that generate braking force can become worn out or damaged. In hydraulic brake systems, issues with the master cylinder or valve can cause the brakes to remain engaged. If any of these components are defective or worn, the brakes may fail to disengage.
   
2. Contaminated Brake Fluid or Air Lines
   For hydraulic and air brake systems, contamination can lead to brake failure. If brake fluid becomes contaminated with water, dirt, or debris, it can affect the pressure levels in the braking system. Similarly, air lines in an air brake system can become clogged with moisture or dirt, leading to a failure in releasing the brakes.
   
3. Improper Brake Adjustment
   Trailer brakes need to be regularly adjusted to ensure they work efficiently. Over time, brake shoes can wear down, or the brake pads may become misaligned. If the brakes are not properly adjusted, they may drag on the drums or discs, making it difficult for them to release after braking. Regular adjustments and maintenance can help prevent this issue.
   
4. Faulty Brake Contactor or Relay
   In electric braking systems, the brake contactor or relay is responsible for completing the circuit that engages the brakes. If these components fail, the circuit may stay open or closed, causing the brakes to remain applied even when they should be disengaged. This issue is often caused by worn-out relays or faulty wiring.
   
5. Brake System Overheating
   When a trailer's brakes overheat due to excessive use or heavy braking, they can become "stuck" in the engaged position. This happens because the brake linings expand from the heat and become less effective at releasing the braking force. This situation is especially common when pulling heavy loads up steep inclines or when making frequent stops.
   

How to Troubleshoot and Solve the Problem

1. Inspect Brake Components
   Start by inspecting the brake components on your trailer. Look for visible signs of damage, wear, or corrosion on the brake pads, shoes, magnets, or cylinders. If any parts appear worn or damaged, they will need to be replaced. Pay special attention to the brake shoes, as these are often the primary cause of dragging brakes if they are misaligned or worn out.
   
2. Check Brake Fluid or Air Lines
   For hydraulic and air brake systems, check the brake fluid level and quality. If the fluid looks contaminated or is low, flush and replace it with fresh fluid. Similarly, check the air lines for leaks, moisture, or blockages. If you find any issues, repair or replace the air lines as needed.
   
3. Adjust the Brakes
   Proper brake adjustment is essential to ensure the brakes release correctly. If you find that the brakes are dragging or not releasing fully, it may be time for an adjustment. Many trailers have a manual adjuster that can be used to ensure the brake shoes are properly aligned with the drums or discs. If the adjustment mechanism seems out of alignment, it may need to be repaired or replaced.
   
4. Inspect the Brake Contactor and Relays
   For electric brake systems, a faulty brake contactor or relay can prevent the brakes from releasing. Check the wiring and ensure that the contacts are not corroded or damaged. If you suspect the relay is malfunctioning, replace it to restore proper brake operation.
   
5. Allow Brakes to Cool Down
   If you’ve been using the trailer heavily, especially for long durations or uphill, give the brakes time to cool down. Overheated brakes can become stuck in the engaged position, and cooling them off can allow them to release naturally. If this problem persists, you may need to have the brake system inspected for any internal damage or wear.
   

Preventing Brake Issues in the Future

1. Regular Maintenance and Inspections
   The best way to prevent brake issues is through regular maintenance. This includes checking the brake system for wear and tear, adjusting the brakes regularly, and replacing any worn components before they cause problems. A periodic inspection, at least once every six months, can identify potential issues before they lead to more significant problems.
   
2. Properly Load Your Trailer
   Overloading your trailer can put excessive strain on the braking system, leading to overheating and premature wear. Always make sure to follow the manufacturer’s guidelines for load capacity. Distribute the load evenly to avoid overloading any one axle, which can cause uneven brake engagement and additional wear.
   
3. Avoid Overuse of Brakes
   Frequent heavy braking, particularly when carrying heavy loads, can cause the brakes to overheat. Use engine braking or downshifting whenever possible to reduce the strain on your trailer’s braking system. Also, give yourself extra space to stop and avoid slamming on the brakes in emergency situations.
   

Conclusion
Trailer brake issues, especially when the brakes won’t release, can cause significant safety hazards and damage to both the trailer and towing vehicle. By understanding the common causes of this issue—such as damaged components, improper adjustments, contaminated fluids, or faulty relays—you can take the necessary steps to troubleshoot and fix the problem. Regular maintenance and proper handling of the trailer will help ensure that the brakes function correctly, extending the lifespan of your trailer and preventing accidents on the road.