flush it with CLR
i read the first four pages of this thread... and didnt see anyone hit solution. I'm short on time and if I dont post now ill forget.
I had the same symptoms in my 01 5.4 EB no AT ALL in front or rear. Yet I had heated lines all the way to the rear. I dremeled a whole in the plenum and could see the blend door moving....
Here's what fixed it for me. I have it on youtube but I dont have the link handy just search heater expedition CLR should pull it up.
Anyway the fix:
Drain the coolant a few times until it drains clear. (After the 3rd time i just opened the drain, then stuck my hose in the fill jug and started the truck. after about ten minutes it actually was clear.)
Go get the prestone flushing kit, the Gallon jug of CLR from home depot, and some antifreeze.
With the coolant system empty poor half the CLR into the radiator and turn your hose on then start your truck as the hose begins to fill the coolant system. I had been fighting this problem so many times I knew how much to turn my hose on to allow me time to make it from the driveway to the spigot to the ignition switch. My approach was get the truck running with the most concentrated amount of CLR flowing as possible. Im not sayin idle your truck with 2 quarts of liquid in it.. im saying start it up as quick as possible while filling it at a moderate speed. once full drive it for ten or so minutes. I suppose you could sit in your driveway and run the rpms up to 3000 for a couple minutes.
Now with it still idling open the drain valve and
I should mention at this point I had rigged up an old piece of hose and hose clamp to direct the flow from the drain valve... if I had not have had a hose on the drain valve the hot coolant would have spewed and maybe splashed me while i was opening it.
so car idling with CLR + water drain, valve open, let your hose add water such that it matches the speed of whats coming out. let all the crap come out till it looks clear again and turn the truck off. and let the water drain back out.
close the drain. install the prestone T fitting and follow their instructions for flushing. I suggest a couple large towels protecting the COPs and injectors from any drippage or if you fubar it like i did and put that valve backwards and spew water all over everything the towels will catch it or give you time to haul ass back to the spigot... it was dark and late and i was cold
anyway after flushing with prestone and filling back up with straight water I found my heat working. The next day it got even warmer. I felt my problem solved so I drained and filled with 50/50. In hindsight I should have flushed it again with the remaining half gallon of CLR and have let it sit for a few hours on the second fill.... then drained and flushed.
You might say well how do you know it was the CLR and not the prestone well because I had flushed this thing a dozen times using prestone and anything else I could find on the shelf at walmart and pepboys over the last three years.
That day I happened to be cleaning something and i realized the correlation between what CLR is meant to clean and what our cooling system is comprised of: water and metal. i went to straight to HD and by 8 that evening I was flushing with CLR. By 9:30 I had heat..
