I have a coolent leak in my Ford E-150 2000?

I have a coolent leak in my Ford E-150, 2000. I have looked and found a large puddle of coolent just ontop of the engine block and under the intake manifold. It leaks quite a lot. I have checked all the hoses and fittings and all is well. The coolent puddles and then runns down the block and un to the ground. Please don't tell me that it has somthing to do with the manifold gasket. Thanks.