The van starts and drives great then suddenly the oil pressure starts dropping until theres no pressure indicated. The engine gets hot and radiator starts boiling. If I allow it to run, the engine starts to race and then stumbles as if to indicate seizure.
What engine?? Miles on van?? You may have two problems. The overheating thins the oil out until it’s like water…If you have driven it for any distance with no oil pressure and the coolant boiling, you may be past the point of no return…
Does the engine have the original timing chain? If so, drain the oil and inspect the oil for small bits of plastic. If any are found the cam timing gear is coming apart.
The teeth on the cam timing gear are made from plastic. These plastic teeth can begin to break off the gear hub and fall into the oil pan. These bits of plastic then accumulate in the oil pan. Then as the engine is running these bits of plastic get drawn onto the oil pump pickup screen and starve the engine of oil. When the engine is turned off, these bits of plastic fall away from the pickup screen. The engine is then restarted and oil pressure is restored until these bits of plastic plug the screen again.
Tester
I’ve added oil stabilizer, engine idled for a long time before pressure went completely. No signs of overheating…