get a empty coke bottle cut off the bottom. Get some thread tape or gaffa tape and keep wrapping it around the mouth piece of the bottle till the mouth piece can sit tight in the radiator fill up point if you think you got it fairly air tight fill up the rad till the bottle is half full. Have you car runing with heater on #2 position, watch the water bubble and go down keep topping up so you dont run the bottle dry and get air back in the system. Once thermo fans kick in the cooling system should be bled. You will notice no more bubbles comming out also.

Simply toping up the rad without a airtight funnel like this home job wont bleed the rad and you will always get the airlock and overheating problem.

Hope it was of some help.

PS: easier if you keep the cap on the bottle and make a 20mm or so hole in the cap and wrap the tape around the cap to make the seal

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