Every time I pull into the driveway or any parking spot, I notice a large puddle of water under my Screw. If it's condensation, where is it coming from and what damage will it do - like rust!!??

 

My best guess is that you are talking about AC condensation- it will be clear water that stops dripping shortly after you turn the AC off.
Air Conditoning 101 - The freon in your air conditioner travels in a sealed loop. The compressor pressurizes the freon. When a gas is pressurized it heats up. The hot, high pressure freon is passed through a radiator called a condensor where the freon gives up heat to the outside air. On your truck the condensor/radiator is located in front of the truck radiator. The cooled, high pressure freon is now a liquid state. The high pressure liquid freon is piped into the cab of the truck where it goes through an expansion valve. The expansion valve acts as a small orifice or hole that offers resistance to flow. When the freon passes through the valve it goes from a high pressure area to a low pressure area. The low pressure causes the cooled liquid freon to expand back into a gas. When a gas is depressurized it gets cooler. The now cold freon gas (appx. 30 degrees F) is passed through another radiator under the dash called the evaporator. The dash fan blows air across the cold evaporator where the air is cooled and then blown out of your dashboard vents. The freon in the evaporator is returned to the compressor as a warm gas and the freon cycle is repeated.

Now for the water. Warm air will hold more water than cold. When you bring a cold beer into a room you usually get water drops condensing on the outside of the glass. This is because the cooled air against the glass won't hold has much humiditiy as it did when it was warm. The moisture is given up as condensation or liquid water - so the outside of the cold beer glass gets wet. It may not happen if the air is dry and gets worse with higher humidity. When the air is blown across the cold evaporator, the evaporator acts like the cold glass and pulls water out of the air. On humid days there can be quite a bit of water running off of the evaporator. The evaporator has a little tray under it and a hose to carry the water out of the cab. The water will pretty much drip the entire time the AC is on and will continue to drip for a short time after the AC is turned off. How much there is depends upon how humid it is that day. Sometimes, in older cars, the hose gets plugged or disconnected and the water drips INSIDE the cab. That is when you need to worry about rust.

 

All cars (with air conditioners) do that..... As long as it's water under your hood you have nothing to worry about. Won't do any more damage than driving in the rain....

 

Since a complete answer has already been given, time for a bit of levity...

Now, if it's the yellow "water" on one of the tires, you gotta ask your neighbor to start leashing their dog.

 

LOL... I hadn't had my new S'Crew home for more than15 minutes before my neighbor's dog came over and marked it as his.

 

Thanks guys for all the comments, including the funny ones!
My only concern was the water was running from under the heat protecting foil. I was not sure this was nornal - then again, what is nornal?

 

Also, the further south you drive the bigger the puddle will be!

 

Now I understand.

 

Excellent response on the A/C 101....we all knew that didn't we???

You could have said that the ac pulls the water out of the air in the cab and it has to drain somewhere...

You forgot to mention the oil in the refrigerant and the pressure/temp relationship....

 

You know, I found a small 1/2" diameter flared open ended tube coming straight down just to the right front of the transfer case. I'm wondering if this is the drain line for the air conditioning....

 

I could be wrong, but I don't think the a/c has a drain line... The condensation forms no different than the condensation on the outside of a glass of ice water.......

 

STX,

Maybe it is a drain outlet for where the water comes down the front of the windshield? I'm not sure, but its there as I saw it last night.

 

I believe it is drain for oil when you remove the oil filter . That way it won't soak the starter .

 

Canyon,

Nope, no joy on that one. No relation to it.....

 

foyboy ,
I had a 99 Ranger and that was what the tube was for in front of the t/case . I haven't looked at my Screw yet ...