Escort diesel van heater cold, replaced thermostat, back filled matrix after flushing in both directions. Engine coming up to temp, fan cycles, heat from block to heater hose, hose to water pump/bottom hose only slightly warm. Air vent on top hose snapped so had to bypass section with hard pipe, no vent valve now!. Removed restrictor from small hose which goes from thermostat housing to expansion tank and T's off to block.