I have a 2004 Taurus with the vulcan engine
If so, do you need to remove the air intake assembly to get back to the firewall and do the work? Doesn't seem like I could get to it otherwise, or am I missing something?
You can do it the difficult way if you want to. Or you can do it the easy way like I did. Here is a step by step of what I did.
1: Get a pair of vise grips, preferably small ones with flat jaws. If those aren't available you can use a C clamp. There's a heater bypass hose behind the engine, it goes straight across above where the heater core goes through the fire wall. Clamp it off, like pinch the hose so water won't be able to flow through.
2: There are two hoses, one that goes to the engine block at the thermostat box. Disconnect it and slap something over the fitting to stop the coolant from draining out of the engine. The second hose is on the left side of the engine near the belts. Pull back the clamp and pull the hose off the metal line. Put a short length of spare hose on the metal pipe if you have some.
3: Get one of those hose nozzles that have adjustable spray, preferably one that has a nose that will fit into the heater hose and seal pretty well. You know, the ones that you squeeze the handle on the back and water sprays out the front? The twist kind *can work but they're hard to handle and turn off and on.
4: Stick the hose nozzle in one of the hoses you disconnected that go to the heater core. Spray for a few seconds to a minute, then release. The pulsing (as seen above) seems to work best. After doing it a few times go over to the other side of the car and run it into the other hose you disconnected. It worked great on my car btw, although it gave me 'warm' rather than real heat.
If possible do try to divert the water coming out away
from the electronics of the engine. Mine decided to misfire for twelve miles after I did the flush since I was sloppy. Also if you wanted to try the alcohol flush, I guess you could blow the water out of the lines with air and pour the alcohol in? If you try it let it soak a while. My only other suggestion is that if your heater core is clogged with stop leak like mine was to be more thorough than I was, in other words don't call it done after flushing for just fifteen minutes. Hope this helps some folks. No sense making more work for yourself when doing it the quick easy way is just as thorough.
5: And oh yeah of course be sure to remove whatever plug you used on that fitting. That and the vise grip or clamp you shut off the bypass hose with, and put all the hoses back on.
Also you might try driving, or at least warming the engine up with the bypass hose clamped. It won't unclog it if it's plugged, but might flush some further crud out of the core.
Good luck hope this helps some folks get it done in this cold weather.