My problem is my heating/cooling system,lower rad hose stays cold but upper rad hose gets hot.Temperature guage climbs to red zone after about 10 mins running,engine power reduces.Replaced thermostat and problem seemed to be rectified,bled air out of system and had heat in cabin,van sat for aprox 3-4 days and issue arose again,needed to bleed system and prime waterpump.Is this an issue of rad having a small leak allowing air in system as I noticed a small amount of steam escaping from top of rad on drivers side.