IF this were the case, pinching off the bypass while the engine is running should flush the air out of the core, no? The bypass hose is there for a reason, to bypass a clogged heater core and keep your Vulcan from overheating. The Vulcan coolant/heat design is a poor one in many aspects and they usually need annual flushing to remain in good working order. Not all clogging contaminants are big chunks of dark crud that you can see. My other questionn would be, how is air getting into your block to cause cavitation? The degasser reservoir (overflow bottle) is supposed to eliminate air from the system. Vulcans also naturally dissolve the vanes on their water pumps and cause poor coolant flow and poor heat in cold climates, which is a whole 'nother bitch of mine....http://www.taurusclub.com/forum/98-...29385-writeup-clinton-gen-3-heater-flush.html
Assuming you have airflow, a dead giveaway is this: turn the heat off after engine has warmed up and continue driving a few miles. Then turn on heat. If you get a brief burst of heat, followed by more cold air, then you need to do the backflush described in the above article.
I have had to do this every winter for the past 3 years. If I had any brains, I'd re-plumb it without the bypass hose, because I believe that bypass hose is the root cause of this. My theory is, regardless of whether the heater core is actually clogged (mine never is), air builds up in the heater core because of cavitation caused by the greater flow through the bypass channel.
Funny how we tend to overlook the simple solutions...This may seem to be a dumb thing to check for when you don't have heat....but I knew someone who didn't have heat, and it ended up being the temperature control knob. The metal tab inside the knob had stripped and turning it was doing nothing. The problem was solved by swapping an adjacent knob off the dash temporarily. Sounds simple to most of us, but this was the problem and the owner was unaware of what was going on.
Check out my thread - http://www.taurusclub.com/forum/82-maintenance-repair/161473-2001-ford-taurus-no-heat-help-3.htmlMy 2000 Taurus 3.0 flex fuel heat has suddenly stopped working. I have replaced the thermostat, check heater hoses which both top and bottom are hot, also checked the blend door and it is working. Any one with ideas please help!!!