Blown Head Gasket
The head gasket's job is to seal the engine's head to the engine's block. It must seal water passages, oil passages, and the engine's compression. When any one of those passages springs a leak - you have a blown head gasket. You can find instructions to replace it in this link Head Gasket Instructions
How to test for a blown head gasket:
Shop Note: be very careful when you remove your old gasket. FOR INSTRUCTIONS CLICK HERE . The LAST tool you should be using is a screwdriver. Use a razor blade and be very careful not to scratch the surface of the block or the head. Scratches and gouges will cause the new head gasket to leak! Be sure both the head & block mating surfaces are completely clean and dry. Install the head gasket dry. Never use silicone on a head gasket. You can use a copper gasket coating spray if you really want to.
Shop Note #2: Use a recently calibrated torque wrench (yes, torque wrenches can get off by a LOT in just a few uses) and it is also a good idea to re-torque your head gasket after a few hours of use. While not 100% necessary in all cases, it is one more piece of insurance against having to do this project again.