How to Do a Four-Point Brake Check
A four-point brake check is often done on large semi trucks to make sure the braking system is operating efficiently. It's obviously important to have your brakes working properly, especially when hauling heavy loads of cargo. This process can be a little challenging, so make sure you have enough time.
- Make sure the air compressor works properly by performing a governor check on your air compressor. Turn the engine on and put the truck in gear. Monitor the air pressure needle until the compressor shuts off. It should shut off around 120-130 pounds per square inch (PSI). Apply brake pressure until the compressor turns back on. The compressor should start again between 85-100 PSI.
- Perform a static check by turning the engine off when the air pressure is at its maximum. Release the brakes and turn the key back on simultaneously. Monitor how much air pressure is lost each minute. You don't want more than three PSI per minute to be lost.
- Inspect the air warning system. Turn the engine off and begin pumping the brakes until the warning light appears. Some trucks even have a warning alarm that goes off. The warning signal should go off between 50-70 PSI.
- Perform a tug test by turning the engine on and let the air pressure build up. Put the truck in low gear and engage the trailer brake and clutch. Watch to see if the trailer brake holds. Repeat this test with the tractor brake. This process could cause a lot of headaches, but will certainly be worth the time.