2004 F250 w/ 6.0 & 187K miles. I've never had a coolant leak or any puddles before. Noticed resevoir tank was empty. Added a gallon of 50/50 to max line when cool. Next day small puddle under truck after driving to work. Same thing after i got home. Did this over the next few days but resevoir level didn't go down that much. It doesn't leak when driving or after I turn truck off. Seems like it takes about an hour to start dripping and doesn't stop for a few hours. Very slow drip. Can't see anything from under hood. Looking from underneath it appears to be coming from the top or back of passenger side head. Not valve cover but where head meets block. Drove 3 miles today and it's leaked more now than before. Resevoir level down. Temp guage doesn't go higher than normal range at any point. Questions I have:
1. Does this sound like a typical head gasket leak or something else?
2. I can't afford a full fix right now (I know what a gasser head gasket costs so I can only imagine how much this one is) so is it safe to just keep adding coolant or will this inevitably cause another serious issue?
3. About how much would fixing it cost if it's a head gasket?
4. I found a product at the parts store that's supposed to permanently fix it. Can't remember name. Disconnect radiator hose, pour product into hose to engine, reattach hose, top off coolant, start and idle at normal operating temp for 20 minutes, turn off, let engine cool & sit for 12 hours min, top off coolant again, start and check guages after normal temp is reached, drive for a while, recheck coolant level, it's fixed!

Does that stuff really work? Is it ok to use on that Powerstroke block or is it designed for gas engines? Doesn't specify on bottle. I'm thinking of trying it due to money issues but I won't if it will harm the engine and cost a ton more in the future to replace full cooling system, heads, or even the whole engine. Oil level is fine and doesn't appear contaminated on dip stick. No smoke in exhaust. Operates completely normal, other than leaking on my driveway. I really do need all thoughts and opinions.

 

Something you might consider,
If possible, get hold of a cooling system pressure tester, and if you apply pressure to the cooling system (no more than is specified on the radiator cap) and you may be able to pinpoint the source. It is always a gamble to continue to drive with an unknown leak because you don't know when it will get really bad. Many times a flashlight and small mirror will allow you to see where you normally would not be able to get close to the area.