I have a 2003 350Z and yesterday while driving the belts suddenly started to squeal and when i slowed down at a light smoke came out from the front of the hood. I found that coolant had sprayed all over the front of the engine/engine bay and on the hood above the front of the engine. I left it since it was getting dark and came back today. The radiator hoses are still attached so I ran it and didn't see any coolant leaks. I drove it home and once it warmed up, the temperature would keep rising if I kept it in gear or accelerated. When I let it coast in neutral, the temperature would drop back down. The coolant tank level did not lower at all from the drive. Any ideas?

 

Could be a radiator cap that's seen better days and can't hold pressure anymore. Trashed water pump maybe?

 

I'm sure you've got it fixed by now, but the same thing happened to me.
My radiator sprung a leak, and the coolant splashed everywhere.
I waited for the engine to cool, filled it up with water, and drove slowly to a mechanic to have the radiator replaced.
Hoses were all fine.

I believe a good mechanic can do a pressure test on the radiator to check for holes, and there is some other gas-test they can do to check if you have any gasket issues from overheating... (check if exhaust gasses are leaking into someplace it shouldn't...)

 

Thanks for the replies. I think it was a radiator leak. I replaced the radiator, 3 main coolant hoses, and drive belts. Haven't had any issues since figuring out how to bleed the air. Even the FSM doesn't have good directions for bleeding the system. Finally found a method after lots of searching. After driving the car, I opened the bleed screw on the heater hose until air started to escape. Did that several times: drove with heat on, turned car off after at temperature or starting to over heat, immediately open the bleed screw slowly just until air escapes then close when starts to make bubbling noise.