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Okay - I figured out something most of these posters may have missed.
Like many of you, I had no meaningful heat in a 1999 Ford Taurus with 90Kmi; V6 3.0 Vulcan engine.
1) After 20 minutes of idle, with the heater set to max-on, one hose to the heater core (on the engine side of the fire wall) would be wicked hot -- i.e. you could grab it for about 2 seconds max.
2) The down side hose had a fairly hot hose -- i.e. you could hold it for about 5 seconds max. So I thought that the air blowing thru the heater core was cooling it off -- naturally the down side hose should be cooler, yet no hot air was coming out (yes blowers ran full speed -- but the air was always coming out cold! {Foot note, like some of prior posters, if you turn the blower off for 2-3 minutes and then turn the blower back on, you will get a burst of nice hot air for about 5 seconds, and then it goes cold!}
3) I flushed the coolant in the engine.
4) I flushed the coolant from the heater core -- both directions, with hot tap water / garden hose, until it would run nice and clear out the other side.
5) I clamped shut that (stoooopid) heater core bypass hose.
6) I changed out the water pump even though the blades on the pump looked just like the newly rebuilt blades.
7) I verified that my heater damper door was not broken (ala www.heatertreater.com ) I verified the door opened and closed easily, and made a nice thump going into each position. 8) I let the engine run with the coolant expansion cap off for 10+ minutes to flush air bubbles out after all reassembly.
9) I topped the coolant off to the "right" level -- for both hot and cold engines.
10) I used those ball float tools to ensure I had the right mix of coolant to water in the system.
11) I let the engine run for an hour, sit overnight in 20 degree F cold and confirmed there were no leaks for sure.
12) I confirmed there was no blockage in the hoses to / from the heater core,
or in the tees where the hoses fork to either the heater core or the bypass hose.
I was beginning to think both the original and the replacement water pumps were the wrong ones -- perhaps too small of a blade/impeller? I was going crazy.
11) So I thought perhaps I should change out the heater core, even though the garden hose water ran through it fine. They cost $55 at Autozone; worth a try. So I ripped out my heater core (see footnote below}. On the outside, it looked like new. Yet despite all the flushing with hot water (for 10-15 minutes!) per step #4 above, I noticed some rusty chunks/flakes poured out after I got it all the way out. So I added more water to this completely removed heater core and vigorously shook the unit and then poured the water out -- LOTS of rust/flakes came out with the water! There was no exterior sign of defect or leaking, but everytime I filled up the heater core with hot water, shook it hard for 10 seconds, and poured the water out, more rust silt would spill out with the water. APPARENTLY FLUSHING WITH THE HEATER CORE IN THE ENGINE IS MARGINAL AT BEST...unless perhaps you have a high=pressure water source...
After installing the new heater core, it all works GREAT -- almost but not quite like new.
I conclude that RUST SCALE on the inner surface of all the heater core tubes was acting like a thermal "insulator".
It did not constrict the flow of water through the core, but it was apparently constricting the flow of temperature from the hot coolant to the metal heater core to the air blowing through it!
FOOTNOTE: TO remove the heater core on this vehicle, most everybody says to pull the entire dash out -- even the steering wheel. I saw a couple posters say to remove the glove box and radio, and radio bracket and ashtray, and then just cut the brace under the glovebox (saber saw with metal blade). Then I made a cut in this triagular brace that allowed me to bend/fold the brace away from the heater core exit path. Finally, with most of the middle screws removed, the plastic dash could be pulled/pryed towards the backseat about 3 inches, which was enough to swap out the core. You do have to remove lots of plastic screws that attach the dash to the metal braces (the screws often point towards the rear of the car.) After the new heater core was in place and working great, I "repaired" the saw -cut brace via a 3" piece of steel, about 1/2" wide and 1/4" thick. I drilled 0.25" clearance holes on each side of where the cut was, and matching tapped 1/4-20 holes in the metal brace. A little bit of countersinking and then flathead screws made the brace under the glovebox almost like new. |
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