What's the temperature gauge say? The fact that it is only doing it on one side makes me think that a thermostat is stuck closed. I would get a digital thermometer and see what temp is on both sides of the engine behind the thermostats. Those handheld thermometers are really handy. You could just take the thermostats out and see what it does. Like others have said 19 lbs. might be too much pressure for your aluminum radiator but if it's rated that high, I don't think it would cause it a hose to blow off. Modern hoses don't blow off. Find out what the maximum pressure rating of the radiator is supposed to be. Carefully grab the upper hoses and see if they warm up the same amounts so you can tell if coolant is flowing through both hoses, or one has a stuck thermostat. If you don't have thermostats, then that blows my hole theory. Check for white smoke out the tailpipe indicating a head gasket or crack. Pull the plugs and inspect them for one that is shiny new looking compared to the others. That's a sign that water is getting into the cylinder, hopefully that's not the problem.
Be careful, if it does have a head gasket filling a cylinder up with coolant, I had a V10 Ford pickup come into the shop blowing white smoke out the tailpipe. I parked it until later that evening and when I went to start it ran about a second and it just went clunk and locked up. It had filled the cylinder with coolant while I let it sit and it bent the rod when I started it. I never made that mistake again.
