Leaking coolant - help!!!

[jd21476]

I drove home the other day and smelled what I thought was coolant. I parked my truck and came out about a half hour later to find a puddle under the passenger side by the firewall. I immediately thought I must have lost my heater core.

I finally got around to pulling it out today (about a week later) and it still looks good. I ran some air through it and could not find a leak and then filled it with water and could not find a leak.

I got under the truck and could not find any leaks in the lines or anything. What else could it be?

**** Also, I have not been getting any heat from the truck lately so that also made me think the heater core was bad.