polo 6n2 air in the cooling system
 

hi every one
i have polo out 2001 diesel sdi 1.9 , i made the water out ,and made new water
and now every time only in morning when i start the car the heat lamp start to flickering i drive some thing like 5 min. then i make the moter off . little time then on again the the lamp is off .. i drive very normal tell i stop again for long time and motor going cold again start again ...so i think there is air in the cooling system .. i searched where i can make the air out but i can not found .... is some one can help me then thank you