These guys are right, and I'll throw in another vote for cracked head.

But...take a close look under the exhaust manifold. You might have to move the skirt in the driver's side wheel well to get there. What does the side of the block look like? Stained? Streaked? Just because it is not puddling, does not mean you don't have an external leak. These engines will also blow out the head gasket from the cooling jacket out on that side of the engine.

Good Luck,
Michael