1975 Renault Clio Heater

Heater problem
1975 Renault Clio Engine Size unknown Two Wheel Drive Manual 76000 miles

heater was not working it was blowing cold air but not hot so I took of the hose to the back of the dash board and cleaned out the hoses cant remember the name of the thing but orange water came out I flushed out the system and tryed it again still no heat I then took out the termostat I put it in boilling water but it did not open any way you can help