Bad coolant leak

Not in a accident, it started before any cold weather came to Raleigh. But, I did notice that I had to start adding water to it during this past summer then about two months ago I was driving down I 40 and my temperature gauge went into red zone. I pulled into a convenience store and it (now I waited for it to cool down ) but it took two to three gallons of water which got me home. However, it started getting to the point where I was putting two gallons just to drive five miles. So I decided not to drive it anymore, but if I put water into the radiator now about after maybe a gallon I look under the van and you can see the water running completely out. It seem like is running not from the front. I did change out the water pump and it is not leaking there. I went on YouTube but really cannot get an image of where all the coolant hoses run. I had two other guys who are back yard mechanics and one told me it might be were a heater hose that attached to a plastic fitting and that. Because it was made might have cracked but I have no idea where it goes or a heater core might be blocked. Then a second guy said it was a freeze plug. But like in the top of my comment it started when the weather was warm here and it will start leaking as soon as I pour water into it even if I did not start it. Has not been started at all. The second guy said it just might be a hose but when it first started I noticed that I had no heat just cold air coming out and if I start it up until it gets hot. (I do have the dog house off) I can hear water back there behind the engine about center of it the water is gurgling but it does that few a very quick times. Like I mentioned earlier it is hard to see where the water is actually leaking from. Thanks guys.

Because I cannot drive it.

Thank you but how can I pressure test it because as soon as I put water in it (or coolant) it starts to run out in a matter of not even a minute, but I do not have the type tools to start taking the engine apart. I cannot see where the leak is. I have had so far four different places for it to be leaking from and in my last comment I said everything that has happened. Sir, thank you for responding back to me it has 265,000 miles on it but it runs great. Thank you.

Thank you for your help. How can I pressure it up when the leak starts as soon as I add water to the radiator?

Okay, thank you sir. How do I add the pressure to it and where I get the dye? Sir, I am completely lost.

Hey Ken my mom passed on so I had to go out of town but I finally got back we talked about my 99 astro van with 4.3 engine about a bad coolant leak you sent me some very good info but I had a chance to jack it up somewhat and I found the leak its on the right side of the engine if your facing the motor I see water running down from behind the power steering pump thank you sincerely Chris