How to Do a Four-Point Brake Checkby Elyse James
A four-point brake check is a very important part of preparing for any trip in a transportation rig. Performing this check will ensure that your truck's braking system is properly calibrated and will keep you safe on the road. You should always complete this four-point brake check before setting out on any trip.
Governor Cut in and Governor Cut Out
Keep the engine running and perform a governor cut out and a governor cut in.
Put the truck in gear and watch the air pressure needle. It should rise to 120-130 psi before the compressor shuts off or cuts out.
Push in both brakes until the compressor cuts back in and the pressure needle rises. The governor cut in should be between 85-100 psi.
Static Check and Applied Pressure
Perform a static check by turning off the engine with maximum air pressure.
Turn the key back on with the brakes released. The air gauge should not lose more than 3 psi per minute when the air pressure stabilizes.
Apply 60-90 psi on the brake pedal and hold, with the parking brakes released. When the system stabilizes, it should not lose more than 4 psi per minute.
Lower Air Warning System and Emergency Brake Pop-out Test
Check the lower air warning system by turning off the engine and pumping the brake until the warning light or alarm is activated. The main air gauge should be in the 50-70 psi range.
Pump the brake until the red dash button pops out. This is an emergency brake pop out test. The yellow dash button should pop out around 45-20 psi. Both brakes are set.
Exit the truck and remove the chocks.
Tug Test and Rolling Service Brake Test
Perform a tug test by restarting the engine and rebuilding your air pressure. Push in the trailer brake while remaining in low gear.
Engage the clutch and see if the brake holds. Pull out the trailer brake and push in the tractor brake. Engage the clutch gradually to see if the brakes will hold.
Perform a rolling service brake test. Get your speed up to 1-2 mph and apply the trailer brake and the foot pedal. The truck should stop without pulling to one side.