1999 Chevy S-10 Coolant Leak

My S10 Blazer has a coolant leak. I can smell the coolant when the truck is running and, when parked, a puddle can be found beneath the left, rear side of the engine. It's very tight in that area, with the steering shaft, brake master cylinder and associated tubing in the way, and from underneath, the exhaust manifold and pipes are in the way. So I can't visually see where the leak is coming from. When the truck is run and then left overnight, coolant continues to drip slowly all night long. Any ideas?