TLDR: I had my van on jack stands, I had replaced the water pump and the radiator and I was letting the oil drain while at the same time filling the new radiator with coolant. I noticed that the new coolant was leaking straight into the oil pan and draining out from the oil pan plug. I'm wondering how coolant can be leaking into the oil pan very quickly and without the engine running? Can anyone tell me what kind of repair would be called for in this situation? Just trying to hit every road block before I send 'er to the scrap heap. Thanks to anyone who replies.

I noticed I was loosing coolant when the weather got a little colder and the heater would only work intermittently. I opened up the radiator and filled it up, it took quite a bit of coolant and top it off. I thought I'll add coolant until the weekend when I can dig into where the leak is. I added coolant every morning that week and this seemed to be working out until that Thursday, It needed 2 gallons of coolant to top it off that day and by the end of the day the engine was getting hot and I had to pull over a couple times to let it cool down to get home. I should have just parked it and used my pickup for Fridays schedule but I did not. I added 2 gallons again to top off the radiator and went to my first job. By the time I got to my first job about 20 minutes away, the coolant was gone and the engine was hot and I had to pull off the road. I let it cool down all the way and added 3 gallons of water to the radiator and headed home to park it until I can look into it. On the way home the engine stopped running while I was driving, it was not over heated when this happened but I pulled off the road and got a tow back to my place. I had a mobile mechanic out to look at it the following Monday and he told me the engine might be fine, that I had a leak from my water pump and It was worth it to replace the water pump because it isn't an expensive part. I replaced the water pump, radiator and thermostat and while I had it up on jack stands I was going to change the oil. While the oil was draining there was definitely coolant in the oil which is not a good sign. I let everything drain out and I figured I'll go ahead with my plan since its already almost done. I started filling the radiator with new coolant and after 3 gallons of new coolant in the radiator I noticed that its just draining out of the oil pan. I've seen plenty of things that suggest a cracked head or a blown gasket up top, but what is puzzling me is that it's leaking very quickly and without the engine/water pump being turned on at all and with no fluid in the cooling system. Right from the radiator to the oil pan with just the force of gravity. I would love to understand what is going on and I appreciate any replies I get. Thanks.