97 Chevy Astro van coolant leak

Your heater core is located under the dash passenger side. Your issue may stem from a loose or broken hose that runs to the back of the intake manifold. Take the engine cover off and examine this hose (passenger side of motor). Check while engine is cold. Fire it up. As it gets hot or pressure builds up you should be able to see your problem. Be careful when you poke around when it is hot. If the hose bursts you will get burned or fluid in your face and eyes.
Do you have a rear seat heater? Check those 2 hoses that run underneath the van from the p side to driver side and into the heater core from underneath the van

Thanks for the replies. It ended up being a leaking intake manifold gasket. Heater core checked out ok.