I bought the car with this problem as previous owner had given up trying to fix it....I like a challenge!
No heater,overheats within 10 minutes of driving.
I have read all the posts on this site and others concerning this problem so armed with this info first step was to check for head gasket leak.
Did a chemical sniffer test and all is well so onward with the bleeding of air.
After many attempts to bleed(car jacked up,heater on,etc,etc) it still overheated but the rad was cold and no heater?
It seemed that the water was not circulating although a new pump had been previously fitted so I pulled the top hose off the rad with the intention to see if the water would flow out of it when I started the engine.
To my surprise there wasnt any water there even though I had bleed it till it came out of the bleed hole,it had gone!
So I poured coolant down the hose into the engine until it flowed out and the same to the rad.
Hose back on fired it up and within 10 minutes all was well,heater working and no overheating!!
I hope this info may help others with the same issues as Ive not read anywhere that the rad could be totally air locked.