Coolant low light

I got a new light on the dash, this one for low coolant.  It seems like my car is the best test harness for warning light testing on the road today.

Checked the coolant reservoir and it was, in fact, empty, so at least I know the sensor's accurate.  But I didn't see a stream of coolant exiting the car.  The cooling system in a car is of the recirculating variety, so the coolant has just the following places to go:

1- Dripping out of the system
Maybe I did a poor job with the water pump and there's a leak.  But why am I not seeing a puddle of coolant?  Maybe the dripping is slow enough or it's making contact with something hot and evaporating?  But where's the steam? Could the leak be occurring at higher pressure, so when the car is stopped idling at slow speed, no leak?
2- Mixing with the fuel, going out the exhaust
This would be worse.  I'm not seeing the white smoke normally indicating this problem.  The oil looks good as well, this would be milky, as the water in the combustion chamber would mix with the oil causing it to look cloudy.  While I've never done a head gasket, this is the fix for this issue.

Better than out through the tail pipe

I went through about a gallon of coolant over a few hundred miles, each time, before filling, looking for a leak and I didn't see anything dripping.  Then, after a nice drive, I pulled into the driveway and found the coolant overflow reservoir yet again empty.  Looking down, my driveway revealed what was hidden to me so far: a nice deposit of fresh coolant.  Not much, so I know the leak is small, probably worse at speed, as this issue as cropped up as I've been taking the car out for progressively longer trips.

Not much of a leak, but enough...

The top of the engine around the water pump was dry, but under the car I see some drips from under the radiator support.  That's probably where we need to start looking.  When I purchased the car, the prior owner told me it was leaking from radiator, but this didn't seem to be a radiator leak, as this part was dry.

Corroded pipe

I filled coolant reservoir at the end of the day and the next morning it was empty.  There's a hose leading away from the reservoir and it joins with a metal "T" joint that looks to be in bad shape and leaking.  The T joint joins the overflow, bottom of the radiator and water pump inlet.  Why something that could corrode like metal?  The parts counter guy and I were discussing and we think it's due to the proximity to the exhaust manifold.  This makes sense.  The reason for using such an inferior material like regular steel probably boiled-down to cheapness on the part of Ford.

Here's a close-up from under the car.   I needed to remove the air dam, held in place by some 8mm bolts and those dastardly plastic screw rivets.  Once removed, I could get a clear line of sight on the problem.



The most leaking seems to be on the end of the pipe heading to the water pump, but the amount of moisture on the pipe itself seems to imply leaking from several spots or it has become porous.  I ordered a replacement (about $40 from FordParts.com, the "official" Ford site seemed to be the only place I could get this) and I should have things back together in a few days.