Just replaced the radiator in my '92 yesterday due to a pin-hole and a leaking fin, now the temp gauge is surging. The temp goes about halfway up the gauge, then back down to around 1/4, then back to 1/2 and then back down to 1/4. It does this "cycle" every couple of minutes or so. I'm fairly certain it's not the thermostat, when they go bad they usually stick open or closed and this thing is back and forth. I'm thinking I have an air pocket somewhere, but I can't find one... Any ideas??