On a 94 Coachmen with combined air and hydraulic brake system, after a fairly short but steep downhill, the brake warning system begins to squawk and braking effectiveness is greatly reduced. The brake warning questions the fluid level, but that is ok. The problem endures for weeks sometimes, long after the vehicle has rested for days. The "cure" comes during subsequent braking when a loud crack is heard in the front part of the vehicle. Does someone have an explanation, and hopefully a fix to avoid this problem?