My van will at times have over heating problems. The issue is a overflow problem. Twice a week or so, when I turn off the engine, coolant will spill out by the over flow tank. What’s could cause this problem. The gauge in the van shows normal range, but I lose about a 1/2 gallon every time.
Try replacing the radiator cap. When they get old they can no longer hold the 15 psi or so to keep the coolant in the radiator. If the new radiator cap does not work then a good mechanic should be able to rectify the situation.