Air brakes using to much air

Leaking wheel seals, worn out shoes, bad slack adjusters, or any one of a number of other issues.
Have you had anyone hit the brakes while you watch the chambers and mechanical bits?

 

Not sure I'm following what you're saying. Is your issue poor stopping power from the brakes? Or is it a lack of reservoir capacity? Or is it a lack of reservoir capacity because you are constantly pumping the brakes?

 

If stopping power is the issue, I'd be checking the linings for contamintation or glazing. If its a lack of air reservoir capacity, I'd try and drain the air tanks from full down to completely empty. Trapped water in the tanks will reduce their capacity.

 

This is a good point, if you don't bother to drain the trailer tank it might be 70% water. I've drained well over a gallon out of trailer tanks, don't think many people bother to open the drain valve. Only thing I miss about running doubles is everyone left the valves open when they dropped.

 

Maybe its the brake lining and or drums itself. Ive seen some lining look really good but when they get old they get hard and or glazed and dont stop worth a dam.
If you have proper air pressure confirmed with a gauge at the pots then id replace your lining and drums with fresh stuff before you kill someone.

 

If the drums are glazed, you aint stopping.

If the diagphram between the spring chamber and the stroker chamber that adds power to your slack adjusters to apply the pads to the drums are bad, you will leak through there.

If your pads are glazed or cooked, you aint stopping.

If your drums are cracked on the inside from too much heat you aint stopping.

If you cannot get inside a certain stroke distance you aint stopping.

 

Straight trucks and buses are required to have a brake inversion valve. One of those systems malfunctioning can cause what you are describing.