Heavy truck air leaks and air brake service

Common situations

• Air pressure won’t build or drops while parked
• Audible leak at a glad hand or a cracked seal
• Air line torn off or pinched between tractor and trailer
• Leaking fitting or line under the frame
• Trailer brakes that won’t release, often in deep cold
• Low-air warning that stays on

What the technician does

The technician finds the leak by ear and with soapy water, replaces common seals, glad hands, hoses and fittings, then checks that pressure builds and the brakes release.

In cold weather, moisture in the air system can freeze and lock a valve or keep the brakes from releasing. Draining the air tanks regularly and maintaining the air dryer lowers that risk.

One important precaution

Do not try to cage or release a spring brake (parking brake) yourself without training: the spring in the brake chamber is under high tension. Keep the truck stopped with the hazard lights on and wait for the unit.

What needs a shop

A failed compressor, a brake chamber to replace or a brake out of adjustment limits often need a shop. The technician will tell you on site, with no improvised repair.

To speed things up

• Where the leak is, if you can hear it: glad hand, under the trailer, near a wheel
• What the gauge shows and whether the warning stays on
• Whether it is the trailer brakes or the tractor that stay applied
• How long the truck has been parked, especially in deep cold