So, you notice a hissing sound coming from your semi-trailer, or you are completing a pre-trip inspection and hear a noise. How do you determine where the noise is coming from and what the cause is so you can fix it? It is important to find it as quickly as possible, as this is not only a problem but also a DOT violation that can cause you to be placed out of service.
Safety Is Always the Priority
Before walking around to find the culprit, safety is always the priority. First, check that the truck and trailer brakes are on so that the rig and trailer are secured and will not roll or move. Also, make sure that the air system has been depressurized. Below are some areas that tend to leak.
Check the Air Lines
Air lines are located behind the driver’s side of the truck/tractor, connecting to the semi-trailer’s back side. There is a service line (blue), an emergency brake line (red), and an electrical line (green). Always check over the hoses to see if any of them have any cracks, possible dry rot, or any other type of damage. They can also not be connected securely from the truck to the trailer.
Gladhands
These are the pieces that connect the airlines to the truck. The seals on the gladhands can eventually wear out and need to be replaced, as they are often coupled and uncoupled.
Couplings/Ferrels/Fittings
Do the connecting couplings, ferrets, and fittings fit tightly onto all the hoses, valves, and the trailer’s air tank?
Valves
Are any valves, such as the emergency brake valve, damaged? Check to make sure all valves are working well and free of damage.
Brake Chambers
Are the seals and where they are mounted tightly
connected?
Airbags
Do any of the 4 airbags have any puncture holes?
How to Identify Leaks Properly
To find a leak, the first test is to listen and see if you can hear where the hissing is coming from. One of the easiest and most common ways to determine the location of a leak is to use soapy water in a spray bottle or to have kids blow bubbles in a spray bottle. Spray the soapy water around the areas that can leak or where you hear hissing coming from. If it is a far reach, soak a rag in soapy water and tape it on the end of a long pole or broom handle to be able to rub the rag on the surface you are checking. If you see bubbles forming, then you have found your leak.
A repair shop might use more advanced methods to look for leaks, such as an ultrasonic leak detector that uses sound waves to find leaks or electronic equipment that uses electrical signals to find leaks. Do you need a professional to check for leaks on your trailer? For all your semi-trailer needs, from renting to repair, contact us today!
