I have spongy brakes but cant find any leaks. I can hear air when I push pedal.

With van off , what does the pedal do after pumping it several times? Also , if rear shoes have excessive clearance , that will cause a LOW pedal. When was the last time they were checked and adjusted? Parking brake MUST be released for this. Air noise is possibly booster , which may or may not be a factor yet. Need to answer the first 2 items.