heater blowing cold air

[myron_whiter]

hi

i have a renault clio 1.2 RN provence and my heater is blowing cold air.
i have had alook and the heater pipe is warming up and the air is still comeing out.
now the other day i was driving and there was a bang and then the heat started to come out. but now its stopted working again
i think its the flap that will open up for the air to come out and i have had a look on some websites and in my user manual and it seems that im right but im not sure on how to fix it,
i dont wont to take it to a garage because renaults cost lots to fix and i was hopeing to do it myself.
CAN ANY1 HELP ME IN MY objectives please..

thankyou very much.

myron whiter...

 

[Alastair.]

remove heater matrix, clean/flush through, also change coolant, and again flush through with water from header tank.

i have done a few now, matrix are always blocking on early clio, normaly due to neglect.

 

[myron_whiter]

thanks m8 i will give that a go 2marrow

 

[Moz168]

Ive got the same problem. I was told its a crack in the head gasket and air is being forced into the system, stopping it from flowing around.
Take the coolant header tank cap off,run the engine till the coolant is warm and does it suddenly all back up and spill over once its really warm?
Also is the top pipe warm and the bottom pipe cold?