mystery coolant loss

[BobD981]

Hey all, Im not sure if theres another thread about this (newbie) but after a vauge search I came up with nothing. Anyway, I seem to be losing coolant, about a gallon a month for the last 3 months. Im not boiling over, degas tank lid has no residue or leaking around cap and Im not seeing any unusual coolant temps... No coolant in engine oil either! No smokin or steaming at the exhaust other than during cold start and no residue on muffler tip either. Im stumped! Side note: during the last two days Ive noticed a dripping around the rear side of the engine to the ground (about a drip every 15 seconds), although this just started and I see no obvious cooling system leaks. It is still cold here and I plug in the block heater on 30* or less nights, and run the h#$! out of the heater on my way to work, which is when I started noticing a loss of coolant. Could my heater core be leaking? Please tell me my head gaskets arent blown! cant afford that nonsense at the moment!

Sorry to be so long winded! Any help is appreciated! Thanks

[BobD981]

To clarify I drive a 2004 6.0L psd all stock with 87,000 miles on it, if that makes a difference!

[Ford625]

If you're able to get ahold of the tool, I would pressurize the system to see where it's leaking from. Usually hooks up the overflow tank and has a pump and a pressure gauge.