I also used Bar's Leak HG repair with good results. It's quite a task to
drain ALL the coolant from your system (I must have had a hose running
through various inlets for 30 minutes or so) but if you do not, you end up
with green jello in your system, unless you use VW coolant, in which case
it's blue. Don't go there.

However, your problem could be a number of things. Are you sure you got all
the air out by opening the screw on the radiator--etc--?