I have a 1999 Chevrolet Camaro with a new radiator and no thermostat sometimes it pumps water sometimes it don't I don't understand why its heating there is no water in the oil.

is the air dam still below the radiator ?? that scoop can get wrecked after many chassis scraps with the concrete blocks. also be sure u bled out all the air from the top hose bleeder valve.

Could be a bad water pump,either the vanes are corroded or the seals are leaking air into the system but not bad enough to leak coolant. These engines need a thermostat, otherwise they will overheat due to the fact that the coolant is moving too fast through the radiator that proper heat transfer cannot happen.

Agree with tennisshoes, also you need a 50/50 mix of antifreeze...Not just water.

Sounds like you may have a clogged rad, rust build-up in the water passages of the block, or a bad water pump. There is definitely air in the block, also causing rad fluid not to flow properly. A good block and rad flush are in order, as well as a new water pump.