Garry, with air brakes you are going to be toast before you hit zero lbs. For you and everyone else on airbrakes the standard is to lock up all four wheels when the tanks get between 20 and 45 lbs. This is a safety thing so you can never be with out brakes. Don't think you can just drive fast until you get to zero because you are going to scare the guy following you to death. If you had a CDL then this is something that is taught and you are required to test that it does happen.
Since you have had one leak then it would be good to run this test on your air brake system This is the procedures you learn while getting a CDL. This procedure will also adjust you air brakes up so it should be done on a regular basis. See the last paragraph on Slack Adjuters.
Brake System Check Procedure
(Note- Damage can occur to your service brakes if pedal is pumped hard while Park/Emergency brake is engaged.)
- Be sure rig is on level ground and/or use chalks
- Start the engine. Let the air pressure build up until the governor activates the air compressor cut-out release of air at about 120-130 psi.
Check the Air Compressor Cut-Out and Cut-In Function
- Release the emergency/parking brake.
- Press the brake pedal several times until you see the needle drop to around 85-90 psi.
At that point the governor should activate the air compressor cut-in and the pressure should build back to 100 psi in about 45 seconds.
Allow the pressure to build to cut-out at about 120-130 psi.
Check for Air Leaks
- Shut off the engine, but leave the ignition in the "on" position.
Watch the gauge for one minute - there shouldn't be more than a 2 psi drop in pressure. (This checks for leaks from the air compressor to the tanks and the one-way check valves.)
- Press the service brake (brake pedal) and hold it down for one minute. There should be no more than a 3 psi drop in pressure. (This checks for leaks with the system under pressure: the air lines, one-way check valves, and Diaphragms.)
Check Audio and Visual Low Air Pressure Alarms/ Adjust Auto Slack Adjusters
- Turn the engine back on and let the compressor build pressure to the air compressor cut-out.
Turn the engine off but leave the ignition switch on.
Smoothly pump the service brake pedal until the low air warning light and buzzer activate. Devices must activate at not less than 60 psi.
Check the Emergency/Parking brake Function
- Continue to pump the service brake pedal until the emergency brake pops out automatically. Application should occur between 20-45 psi.
Start the engine and allow the air compressor to reach cut-out level.
Remove any wheel chalks.
Shift into gear.
Apply your accelerator, but not over 1000 RPM.
Your Rig should not move.
NOTE: Slack Adjustment
Ensure reservoir air pressure is above 90 lbs on both air tanks and make a FULL brake application and release (Hard application to the floor). Repeat this process 6 times. (These brake applications will be adequate to cause the automatic slack adjusters to adjust)
Note: A light brake application will not cause the adjustment
Linear Mode
