Brumini

My 1995 Monaco Dynasty dumps all of the air in the system when set. Then it will not build air again unless I hold the parking brake button down hard until it is over 20 psi. After that it fills to 120 psi like normal until I set the parking brake again. I can hear air under it in front of the rear axle coming from opening on the valve shown. It looks like that is a standard place where air is released when needed but the parking brake should not drain the entire system. Does anyone know where I should start checking things?

My 1995 Monaco Dynasty dumps all of the air in the system when set. Then it will not build air again unless I hold the parking brake button down hard until it is over 20 psi. After that it fills to 120 psi like normal until I set the parking brake again. I can hear air under it in front of the rear axle coming from opening on the valve shown. It looks like that is a standard place where air is released when needed but the parking brake should not drain the entire system. Does anyone know where I should start checking things?