Sounds like either the thermostat is stuck shut, or the electric radiator fan is not working, or the head gasket is damaged. Here's a way to sort that out: Before beginning this test, when the van hasn't been run for at least 6 hours; remove the radiator cap, and fill the radiator to overflowing with a mixture of equal amounts of coolant and distilled water and replace the radiator cap. Then start the engine, let it idle for three minutes, and watch the temperature gauge. The gauge should not move much or at all in the first 3 minutes. After 3 minutes running, take off the radiator cap, and see whether there is pressure in the system (there normally should not be pressure built up in that short a time). If there is much pressure in the system; the head gasket is probably bad, and that is what is causing the overheating. This can happen easily if the engine is allowed to get too hot on even one occasion. In that case, you're in for an expensive repair.
But if there is little or no pressure in the radiator after the first 3 minutes of running; reinstall the radiator cap and drive the van and see what happens with the temperature gauge. The needle should go up to somewhere between 1/4 and 1/2 of the way up the gauge, and then stay there. If the needle reaches 1/2 within the first 3 miles and keeps climbing; shut the motor off well before it reaches the hot zone. This would suggest the thermostat is stuck shut. Buy and install a new thermostat, gasket, and o-ring. Refill the cooling system to overflowing, and repeat the test. Be sure to purge any trapped air from the system (by opening the air bleed valve near the thermostat housing and adding more coolant until it flows out of the bleed valve in a steady stream without bubbles) before driving the car. Then test it again.
If it stays at normal temperature for 5 minutes or more, and then gradually heats up beyond that point; the radiator may need flushing. The electric radiator fan should come on when the temperature reaches 2/3 or 3/4 of the gauge travel. You can open the hood to see if the fan runs, and it should also make noise when it runs. If the fan does not come on; try replacing the fan relay or thermal fan switch. You'll need to speak to a dealer to find out which of those parts are used on your car.
The cooling system should also be pressure tested to see if there are any remaining leaks; and whether the water pump is leaking.