On my 2000 Ford Windstar when I step hard on the gas I have a coolant leak from the back side of the motor and had antifreeze coming up onto the windshield when I turned on the heat. I took the van into the shop and they did a pressure test on it and could not find any leaks and after this I didn’t notice any leaks or smell of antifreeze. Drove the van 400 miles with no problem but last Friday I had to step on the gas to exit a parking lot and then again I smelled coolant and my van was steaming. I added coolant and drove it and it is fine now. There is no oil in the coolant tank.
There is a couple of hoses that go through the firewall for the heater core. Have you tried warming up the van and with the hood open, stepping on the gas to see if you can see the leak?
You have a leak in your heater core. Your symptoms are classic.
The heater core is a small radiator between your dash and your firewall (the back wall of the engine compartment) and when they leak they do exactly as you’re describing.
You may be lucky and it’s one of the hoses to your heater core.
If the coolant is hitting the outside of the windshield, it most likely is a heater hose or the heater control valve that is located in the heater hose in front of the firewall.