Now that you have the air box cutout bring the truck upto operating temp and place your hand on the heat core , it should be very hot! See if the bottom of core is just as hot.

If you hook a garden hose through 1 hose and it come out the other the core is clear. If it dosent you might try tapping on the core while flushing it (lightly). Its hard to belive that a core would clog up with less than a year in service. If thats not whats wrond I would head for the water pump.

At least now you ready for the blend door when it goes out.

good luck

I did see another poster who said that he replaced the water pump and it solved his problem. But wouldn't a bad water pump create higher operating temperatures for the engine coolant? Mine is still running steady temperature wise. Not just the gauge either, I have the Edge programmer that shows a specific number for temperature, so if it varies, I will know.

I still haven't had a chance to flush the core to see if it's clogged, that will be the next step.

This is a good question!
I would think that it would but I also think the t-stat would sence this and open more, you wouldent see this on your dash guage. You would still have poor circulation.

A water pump circulation test would be to let the truck warm up then squeeze the top rad hose, then let off, you should feel a surge of coolant passing through the hose quickly.

Their no chance that the fan belt is sliping? Right!

waiting to hear how things turn out after fulshing those heater hoses.
Let us know.

In this post their is a picture of a worn out impeller in a water pump.

http://www.fordf150.net/forums/viewt...p?f=71&t=80788

WOW! That's not wear, that's severe neglect. If your cooling system is that corrosive, you'd better plan on a radiator and heater core change. That's the worst impeller I've ever seen. I would think he'd have had cooling issues long before it got that bad.

Here ia the rest of the story that goes with that picture. Looks like it had 150k on the truck. He was actually driving it like this.


http://www.fordf150.net/forums/viewtopic.php?t=47398

Well I had some electrical problems on Friday that I had to work on. (It's under the discussion forum "1997-2003 F150" under HELP!?! Truck stuck at work!)

Anyway once I figured out what that problem was, the heater started working again! Worked all day Saturday and Sunday, but I get in this morning and it's back out again...

Weird. Still haven't had a chance to flush it, because I thought it was fixed...