Well, you have a leak somewhere, all right. Finding exactly where is going to be the tricky part, since you say it's wet under the radiator AND on the water pump. Usually a wet radiator means either a leaky radiator or a bad hose. You're right about water pumps telling you when they're going out. There's a weep hole somewhere around the impeller shaft, and it's supposed to leak when the seals in the pump go bad. This doesn't always happen. When I was changing my oil a couple days ago, I noticed a little trickle running down the timing cover, eminating from the water pump mounting flange. My water pump gasket is going, and I'm losing about a half quart of coolant a week.
The system still holds pressure fine, so it's not too bad.
Back to your problem, I'd seriously check out the pump and be sure it's not the culprit. Is your system holding pressure? When's the last time you replaced the radiator cap? Take it to a parts store and have it tested to be sure it's working properly. Assuming the pump is not at fault, and that the fan is just spraying coolant onto the top of the pump (it'll happen),
AND that your hoses are in good shape, your radiator needs replacing. For the price and ease of installation of a new radiator, DON'T use some cheap radiator sealant you dump in. They have a bad habit of clogging heater cores and other nasty things. A new water pump can be had for about $20-30, and a new radiator for $70-85. Most places will give you a lifetime warranty on each. The other alternative is to solder the radiator yourself or find a friend or shop that can do it for you. It's easy to do and works great, but if you have ONE hole in the radiator now, you'll have a LOT later. Trust me on that.
Good luck.
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Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch 
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