Preventing Air Brake System Leaks

Preventing air brake system leaks is critical to safe trucking operations.

Did you know that air brake system hoses and tube violations are the second most common vehicle maintenance DOT violation? In fact, almost 200,000 trucks or trailers a year are cited with a violation of 49 CFR 393.45.

Let’s review the most common violations and find out how to prevent them from hurting your CSA BASIC scores.  

The CVSA has recently released the results of their Brake Safety Week that was held between August 21-27 this year. This annual enforcement blitz takes place near the end of each summer and is like a mini-International Roadcheck event.

Commercial vehicle inspectors perform thousands of Level 1 DOT inspections across North America in an attempt to curb dangerous vehicle conditions.   

13.3% of vehicles inspected during the event were placed Out of Service for air brake system related issues. That breaks down to about 5,000 vehicles being removed from the roadways until needed repairs could be made.

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  5. Preventing Brake Hose and Tube Violations

The inspection focus this year was air brake hose and tube chaffing violations, which are a very common vehicle maintenance violation.  

In fact, through the first 10 months of 2022, there have been 179,257 violations issued for brake hose or tubing issues.

Taken together, this makes air brake system hose and tubing issues the second most common vehicle violation, behind inoperable required lamps.

Here is a breakdown of these violations: (The # on the right represents the number of violations issued so far this year):

Almost 200,000 air brake system hose and tube violations are issued each year.

393.45(b)(2) Brake Hose or Tubing Chafing and/or Kinking 48,082

393.45(b)(2) Brake Hose or Tubing Chafing and/or Kinking Under Vehicle: 33,627

393.45 Brake Tubing and Hose Adequacy 25,181

393.45(d) Brake Connection with Leaks or Constrictions 24,176

393.45DLUV Brake Connections with Leaks Under Vehicle: 16,018

393.45B2PC Brake Hose or Tubing Chafing and/or Kinking – Connection to Power Unit: 14,285

393.45DLPC Brake Connections with Leaks -Connection to Power Unit 9,924

393.45PC Brake Tubing and Hose Adequacy -Connection to Power Unit 4,231

393.45PC Brake Tubing and Hose Adequacy -Under Vehicle 3,733

An air brake leak and brake hose/tube chaffing are the most common types of violations.

Learn more about upcoming changes to how the FMCSA will be calculating Vehicle Maintenance and other CSA scores in 2023 here.

Detecting Air Brake Leaks

There are 3 tell-tale signs of a possible air brake system leak. Start your air brake system troubleshooting by looking for:

  • Loss of brake pressure. The most common sign of a leak in the gladhand seals is the loss of air brake pressure. When doing an air brake leak test, your truck’s air brake system should be able to reach operating pressure within 45 seconds or less. If the system takes more time than that to come up to pressure, it may indicate a leak somewhere in the brake lines.
  • Loss of braking power. If enough pressure is braking power is lost, the brakes will be weaker and feel “squishy”.
  • A loud hissing noise when the parking or service brakes are applied. This usually means that pressurized air is leaking out from the gladhand seal or somewhere along the air brake system lines.

We help track vehicle maintenance inspections and provide specific training on brake maintenance and many other topics as part of our comprehensive DOT compliance services offering!

Air Brake Leak Prevention

Doing a 2- or 3-minute walk around inspection of the truck and trailer and listening for audible leaks is a simple test for locating leaks in an air brake system.  

A good time to do this is when your checking each of your tires to help ensure compliance with the DOT tire regulations.

An air brake leak from the gladhand seals between the truck’s air lines and the trailer air brake connections are the usual place for air leaks for the air brake system in trucks.

Additionally, if a DOT inspector pulls you over and conducts a Level 3 DOT inspection, hearing a leaking gladhand seal may cause him to upgrade your inspection to a DOT Level 2 inspection or even a Level 1 DOT inspection. We call this “inspection creep”.

As a rule of thumb, all gladhand seals should be replaced at least once every year or whenever the air lines have also been replaced.

Rubber glad hand seals are cheaper and more common than their polyurethane counterparts. But they also tend to become brittle and crack over time especially in areas with larger temperature changes. It’s usually worth it to invest a few dollars extra in the poly seals.

Replacing a Gladhand Seal

You should always keep a few extra seals in your truck to make quick repairs if you determine that one of your seals may be faulty.  

Replacing a gladhand seal is easy to do and the only tool that you need is a flathead screwdriver.

  1. Carefully insert the screwdriver between the gladhand body and the gladhand seal.
  2. Pop the old seal out.
  3. Clean the gladhand body to ensure it is free from debris.
  4. Then, firmly place the new gladhand seal into the gladhand body and you’re good to go.
  5. Once you re-connect the gladhands to the trailer air brake connections, perform another air brake leak down test.

If you’re still not building up to the correct pressure in under a minute or still experiencing issues, you’ll need to continue your air brake system troubleshooting.     

Common Causes of Air Brake System Hose Chaffing

Most air brake system chaffing and kinking issues come from one of two different culprits:

  1. A loose or damaged hose tender (or hose spring).
  2. Improper air brake hose placement after a trailer repair
Air Brake Hoses Touching the Truck's Catwalk  is a Leading Cause of Hose Chaffing.

Truck Hose Tender Issues

A truck’s hose tender tends to wear out over time.

When it does, the pigtails are allowed to rub against the truck’s catwalk. This causes the air lines to chaff, and this will eventually lead to a violation and/or a decrease in the air brake system performance.

During your pre-trip inspection or post trip inspection, just check the truck’s catwalk to ensure that all hoses are up off the truck’s deck and free of any kinks in the lines.

Under Vehicle Brake Hose Chaffing

Most under vehicle chaffing and kinking issues are caused when trailer repairs are made.

After completing a repair, maintenance techs must ensure that they reinstall all clamps, tie-downs, and hose routing hardware correctly.

If they don’t, there is a good opportunity for brake hoses to rub and chaff against the frame rails, chassis, axles, or tires.  Lines that span open spaces under the trailer are typically the most prone to issues. Inspect these lines very well too!  

Preventing Under Vehicle Hose Chaffing/Kinking

Be sure to do a thorough inspection of all brake air lines after any trailer repair to ensure that all hoses are routed correctly and secured properly to prevent excessive movement.

Doing a quick walk around inspection can help prevent most common brake hose and tube issues. But, some of the under vehicle violations may only revealed during a truck and trailer’s annual DOT inspection.

FMCSA Air Brake System Hose and Tube Regulations

Here is exactly what the FMCSA says about air brake hose and tube maintenance:

§ 393.45 Brake tubing and hoses; hose assemblies and end fittings

(a) General construction requirements for tubing and hoses, assemblies, and end fittings. 

All brake tubing and hoses, brake hose assemblies, and brake hose end fittings must meet the applicable requirements of FMVSS No. 106 (49 CFR 571.106).

(b) Brake tubing and hose installation. Brake tubing and hose must –

(1) Be long and flexible enough to accommodate without damage all normal motions of the parts to which it is attached;

(2) Be secured against chaffing, kinking, or other mechanical damage; and

(3) Be installed in a manner that prevents it from contacting the vehicle’s exhaust system or any other source of high temperatures.

(c) Nonmetallic brake tubing. Coiled nonmetallic brake tubing may be used for connections between towed and towing motor vehicles or between the frame of a towed vehicle and the unsprung subframe of an adjustable axle of the motor vehicle if –

(1) The coiled tubing has a straight segment (pigtail) at each end that is at least 51 mm (2 inches) in length and is encased in a spring guard or similar device which prevents the tubing from kinking at the fitting at which it is attached to the vehicle; and

(2) The spring guard or similar device has at least 51 mm (2 inches) of closed coils or similar surface at its interface with the fitting and extends at least 38 mm (1 1/2 inches) into the coiled segment of the tubing from its straight segment.

(d) Brake tubing and hose connections. All connections for air, vacuum, or hydraulic braking systems shall be installed so as to ensure an attachment free of leaks, constrictions or other conditions which would adversely affect the performance of the brake system.

How Air Brake System Hoses Fail Inspection

In Appendix A of Part 396, the FMCSA more clearly outlines what is expected when a driver or vehicle inspector reviews a commercial motor vehicle:

Appendix A to Part 396 – Minimum Periodic Inspection Standards

A vehicle does not pass an inspection if it has one of the following defects or deficiencies:

49 CFR Appendix A to Part 396 1.d

d. Brake Hose.

(1) Hose with any damage extending through the outer reinforcement ply. (Rubber impregnated fabric cover is not a reinforcement ply). (Thermoplastic nylon may have braid reinforcement or color difference between cover and inner tube. Exposure of second color is cause for rejection.

(2) Bulge or swelling when air pressure is applied.

(3) Any audible leaks.

(4) Two hoses improperly joined (such as a splice made by sliding the hose ends over a piece of tubing and clamping the hose to the tube).

(5) Air hose cracked, broken or crimped.

e. Brake Tubing.

(1) Any audible leak.

(2) Tubing cracked, damaged by heat, broken or crimped.

Final Thoughts

As you can see, the FMCSA is serious about success here. Fortunately, these common air brake system issues are pretty simple to fix before they show up on a DVER.

The key to avoiding these air brake system violations is proper inspection!

Just be sure to regularly check your truck’s deck to make sure that the air and electrical lines are not rubbing against the catwalk and listen closely to ensure that there are no audible leaks as you walk around your truck and trailer.

If you have any repairs made to your trailer, do a thorough inspection to ensure that all hoses and tubes are properly secured and free of excessive movement.

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