1998 Taurus, 3.0L, Vulcan, no automatic climate control. I've spent many hours searching and reading and trying things, but still have no heat.
Symptoms - No trace of heat inside car. Blower works fine. Heater core hoses at firewall are same temperature, but not hot like the bypass hose. The rubber hoses up to the metal hoses (firewall side of bypass tee) are hot, but the metal hoses and hoses connecting right to the heater core are just a bit warm, but not a temperature differential between the two. Car running at normal operating range. Car does not overheat on long trips. Degas tank full. Coolant looks all brown and corroded. Disclaimer: Wife's car and she did say that the heater worked a few times, but I haven't experienced that, and she hasn't now lately. Problem has been going on about a month, but that's about when we started using the heater too. We did have a problem over the summer where the coolant leaked out and got real low, which turned out to be a cracked degas (overlow) resevoir.
My possible problems: Blocked heater core, bad thermostat, low fluid level, water pump impeller rot, air pocket in cooling system, bad blend door actuator, bad blend door, or stratification (secondary) temperature blend door problem (Ford TS
What I've done: 1) Made sure coolant level was full to within a few inches in resevoir. 2) Disconnected hoses and directly flushed and backflushed heater core 3 times with garden hose. Water ran freely either way each time and there was not a lot of crud coming out although the overall coolant is brown and ugly. 3) Tried pinching off bypass hose, still no heat. 4) replaced thermostat, no change in engine temperature, so even though it looked very rusty it was still working. 5) tried bleeding the air out by disconnecting the hose that leads into the degas overflow tank (originates from top of thermostat). There was not a constant stream of water flow but came in spurts, running for a bit and then not. I presumed this was due to the thermostat opening and closing. 6) Disconnected heater hose coming from the water pump but after the bypass tee, and started the engine. Pretty sure I had the bypass hose clamped off too. Water would flow out of the hose at a good rate, but again it would flow for awhile and then not. While the water was coming out (and very hot I might add) I connected it up to the metal tube that goes to the heater core and checked the air inside the compartment, but still ice cold. 7) Took off the blend door actuator and confirmed that it moved the full range, about 90 degrees, while I turned the manual heat control knob. 8) Inspected the fitting that the actuator goes into and made sure that piece wasn't broken. 9) moved the metal lever up and down that controls the blend door and listened to different sounds of air, seeming to say that it was working. 10) went ahead and did a quick flush of whole system and added new antifreeze since it is now snowing outside, ugh!
What next? My thoughts right now are either 1) the water pump isn't quite pumping right, although the car does not overheat and water was flowing well through the heater hose today, or 2) the stratification (secondary) temperature blend door (whatever that is, there was a TSB
on it anyway), or 3) the heater core is shot, even though it is not leaking inside and water is flowing through it.
My guess right now is #2, the secondary blend door thing. Can someone tell me how to get at that? I have the instrument panel off, glove box out, blend door actuator out, and can get at the cover of the heater core, but I have no idea how or where to get at this secondary blend door. Here is the TSB
for it, but I still can't figure it out. http://ford.justanswer.com/uploads/fordguy...TSB-02-23-6.pdf
What is the plenum? I've tried searching for pictures but have had no luck. I'm still not 100% convinced that water is really flowing through the heater core, but everything I've done says it should be and yet not even a little warm air coming out.
OR, if there is something I'm missing or overlooking or making the wrong assumptions about, then by all means let me know! I'm open to ideas. The car isn't worth what the dealer would charge me to fix this.