Drove the car for about 2 minutes tonight and notice that the temp has hit the red. Pull up and see that the overflow bottle which always sits at about 1/4 full when hot has overflowed. Let it cool down, fired up again and refilled the rad with the engine running. It got hot within a minute or 2 again. There was little flow when I first fired up but then it looks like the stat opened and then the coolant was just spurting out the radiator fill neck. Normally I can run it with the cap off and the stat open and at idle it just flows around without spurting out the neck. WTF?? It's a new L98 engine but has been running like a beaut for nearly 6 weeks. Sticky 'stat, crook pump or what??

 

check your lower radiator hose it may be sucking itself closed and not letting the coolant flow through the motor, instead the pump is just pumping it out of the overflow and neck.