coolant leak getting worse!

for a few weeks now my truck has been dripping antifreeze from the back of the motor, but at such a slow rate i only need to top off the coolant once a week or so. I was running through some mud earlier tonight and noticed i was running a little hotter than usual, so i got it home and pulled in the driveway. When i got out there was already a puddle of coolant on the ground and when i looked under the truck I could see it dripping from the same place only much faster. I'm thinking maybe I ran through some water and caused an already ruptured freeze plug to crack worse? The truck leaks even if it's shut off. Another thing i noticed is that even with the temp guage above 210, the rad cap was still cool and didn't vent any pressure when i removed it. What the hell? If the thermostat wasn't opening then how could coolant be circulating through the block to the freeze plug that's leaking? I've checked the intake manifold and heads for leaks and there are none. I'm stumped and I really want some insight before I decide to pull the tranny only to find the plugs are fine.

I'd check the intake manifold gasket again, they are prone to leak on the 4.3L (that is if it is a 4.3L)

If there's an air pocket in your engine the thermostat doesn't have a chance of opening, and if you don't have enough coolant you probably have an air pocket.

If it's a 4x4 it's usually easier to remove the motor than pull the transmssion.

Have you checked all the hoses and fittings? I had that problem a few years ago and it turned out to be that the hose going into the heater core had a small pinhole size crack in it right at the firewall. It took me weeks to find it because it wasn't leaving any antifreeze on the firewall.. and looking under the truck it looked like it was coming from the rear of the engine.

... took the truck to my mechanic who put it up on the lift, took one look at the leak and said "yep, bad freeze plug." So it's sitting at the shop awaiting new brass plugs. I shouldn't complain though, he's doing it all for around 200 bux, which isn't too bad for having to drop the transmission. while he has it apart i'm having him inspect the clutch assembly for wear... which i will have replaced while the tranny is dropped to save some money in labor in the long run. peace