I transplanted a G160 from a D15 tractor into my D12 for pulling. I had already had the tractor running last week but before I fired it up last night I decided to fill the radiator with water before a test drive. To my surprise, it took a lot of water as I filled it until I notice water overflowing out of the dipstick hole. All coolant I put into the radiator went straight into the crankcase. What causes this? The engine has been a mess as I bought it sight unseen and have had to fix a few other things. This is just the latest issue. I am thinking of dropping the pan and running water through the radiator to see where it's coming into the crankcase. Where ever it's getting in, it's flowing pretty freely. Thoughts?