I walked across a parking lot the other day and noticed something leaking from my ugly but reliable f150. It turned out to be coolant, and they were very steady drips from the back and driver's side of the engine. I popped the hood, but there's so much stuff in the way (plus I've never degreased this thing and it's freakin' filthy) that I couldn't see any place leaking. I checked all of the obvious places--the main cooling and heater hoses, water pump, small bypass hoses to the intake system etc, but couldn't spot where it was coming from.

Oh, and I didn't see any liquid on top of the intake.

Anyway, I poured about a gallon of water in the radiator and made for home. The temp didn't come up at all on the way, and it didn't appear to have lost much if any coolant when I arrived. A few days and several hundred miles later, it's once again showing low coolant. It doesn't get hot and it doesn't keep leaking. It seems to go down to a certain point and stay there until I add more to the radiator.

I was thinking a freeze plug or two might have developed a leak but that can't be...can it?

Cheers,
Q