My chevy Venture van still overheating after radiator replaced, temp gauge replaced and fans fixed. WHY?

If the other possibilities are ruled out, you could have blockage in the radiator. Here's a simple but somewhat messy way to test for blockage. Drain he radiator. Disconnect upper and lower radiator hoses. When all water has drained out, cap the lower radiator outlet with a piece of plastic and tie it with rubber bands. Fill the radiator to top, then suddenly remove the plastic and observe the discharge. A good radiator will shoot water a half foot horizontally. A partially blocked radiator usually runs fairly quick, but doesn't shoot the water.

Water pump? or thermostat?
When the vehicle is cooled down,
open radiator cap, start car, running and heat on
You should see circulation or air bubbles at the radiator in let, if not probably water pump or tstat?
Hope this helps?

You may have air trapped in the cooling system. This will cause overheating. When you fill the system, there is a small brass air purge valve above the coolant pump and another on the thermostat housing. These need to be loosened and trapped air released when filling the cooling system.

I agree with the head gasket answer.I've had to chaneg 5 of them on customer vehicles so far

If your engine is overheating, Try this procedure:

• Dirt and debris can get lodged in the radiator air flow paths. This can block the radiator and cause your engine to overheat and damage the engine.

• The thermostat can be stuck close. If you feel the upper hose very hot and the lower hose cooler than normal, it may be a stuck thermostat.

• Make sure the radiator and the overflow bottle are filled to the proper levels.

• Bleed air from the coolant system:This is best done by running the engine with the radiator cap off until you see when the air bubbles stop coming up.

• Check the radiator fans: The easiest way is to turn on the cars air conditioner and turn up the A/C fans. Both radiator fans should come on when the A/C starts

• Make a pressure test by using a pressure testing tool (available at most auto parts stores). Use the pressure shown on your radiator cap. Most cars are 16 PSI or less, so don't exceed that pressure. Replace the radiator cap if it doesn't hold the pressure.