So my heat's been sub par lately. Cold nights recently I have little heat when driving or idling, and at times, it will heat up when driving. Took about 20 min or so 2day to get the truck to temp, when it was 54 and sunny out. Drove thru town, n realized my heat was hotter than the fires of damnation. 1st time in a while it's been like this. I do have what is a small leak coming from the coolant line under the intake manifold, but it's minuscule at best. I do have to flush the system, and replace the stat which I already picked up.

Now I have 2 lines coming from the top of the firewall, out to an aluminum T, those 2 lines branch down to a set of aluminum pipes, one connected to the radiator and the other disappears I believe back thru the firewall. The other direction from the T is one to the front of the engine along the pass side, and the other branches down to where I couldn't see at that moment. They both feel hot, but not sure which is IN and which is OUT, since I would like to back flush the heater core. I have NO heat what so ever for the rear air.

2000 Expy 4.6L Dual Rad w/ Rear Air

 

2000 Ford Expedition - Coolant System Flush with Degas Bottle - Clean and Thorough - YouTube
I was tempted to do this flush with my '01. I didn't want to screw with a t-stat that is working fine. I can't speak for the wisdom of this procedure. Purely FYI.

 

My friend Matt who worked for Ford used to do something similar, but he's let it run for about 2hrs with the garden hose attached. What I want to do is push water and Prestone Flush through the system with some compressed air, through the OUT hose from the heater core. I think I may look up at Heater Core removal guide and see if the hose directions are described there. But thank.

 

And I just found it, the hose that T's off and goes below the side of the engine is the OUT hose it connects to the water pump. Thats the one I need to flush backwards thru the IN hose which is the hose that guy in the video tapped into. I may hook up a wet/dry vac to the IN, to alleviate pressure from the Heater Core, and still have a backwards pass thru against the normal flow, to loosen anything up inside.

 

Wanted to correct my previous statement, I did find the hose but they both T down to the oil cooler pump behind and below the battery. Disconnecting them from there is a bit easier, for they have press clips on them, similar to a disconnect. Once they're disconnected you can twist the hoses looses at the T. Right now I'm gonna need to wrestle the hose off the engine near the front of the manifold, this ones gimme me an ulcer, not wanting to come off. I did also manage to find one engine block drain, above the oil pan, and this is good info for others the 4.6L came with 2 or 3 different plugs, mine is an 18mm 6 star socket, others came with Hex or standard 3/8" socket plugs like you'd find on the transfer case or rear diff. It's located near the block plug, above the oil pan between cylinders 7 n 8 I believe on the drivers side. Found this out via the Mustang Forums. I've read the Passenger side block drain is behind the starter. Gonna start looking later, once the sun is fully in the sky, and it's a bit warmer. Planned on doing this, this past Monday when it was 60 out, but nothing like other people to screw you. The hoses I did pull from the oil pump cooler as well as the top rad hose with the thermostat revealed a lot of sediment, from rust and such.