99 Taurus Heater Problem Daughters'

[ftt77]

When touching the heater core inlet and outlet, one is hot and one is cold.
I disconnect the hoses and flushed the heater core and did get goodflow thru it in both directons. I then ran the car and again, hot on one side and cold on the other. Its my daughters car and she says that since I flushed it, it will get hot and stay hot for a while and then after 30 min. it will get cold again. I have changed the thermostats twice. It does have a wierd hose system that has a couple of T's in it that feed the heater core and return from the heater core. One of the on the t's on the cold side has little marks like > < etc on the plastic t. I am guessing that those are non-electrical check or flow controllers in the hose system. The hoses do not remove from them and you have to buy the whole $81 hose system so I cannot tell if they are good or bad. I am at a loss as to what would cause the heat to be good and then change and be cold. Any ideas would be greatly appreciated.
Thank You

[shorod]

Bad water pump impellers have been a common issue on the Taurus. That could possibly explain why your daughter is experiencing this. The cooling system flow is poor, so with the blower running across the heater core, after some amount of time, the coolant in the core cools from the blower motor and stops blowing hot. The pump is not circulating fresh, hot coolant through the core.

You should also verify that there are no air bubbles trapped in the cooling system, and you may want to make sure the thermostat is operating properly.

Has she been keeping an eye on her temperature guage while driving?

-Rod

[ftt77]

Thanks Rod for that information. You have touched on an area concerning the water pump that I would have never have thought of. I have another Taurus that I can switch the heater hoses out with to see if its in that plastic check valve thing. If that makes no difference, and since I can easily flush thru the heater core and I am sure the thermostat is working, I am thinking your water pump intermitten problem makes the most sense. I cannot think of anything else except the thermostat that would cause the heater core temp to be fine for 30 minutes and then stop being fine and going cold. I believe your water pump impeller might be the best explanation.
Unfortunately there is not temp gauge in this car, just idiot lights.
Thanks again. I would much rather tackel a water pump than a heater core. Heater core replacements on these according to the book is a full dashboard removal or $600 minimum from the auto shop.
I appreciate your time
Forrest

[medicmandan]

I had the exact same problem with my 99 Taurus. The hose from thermostat to heater core was hot, the one from heater core to water pump was cold. Flushed the heater core, got a bunch of garbage out but it still didn't help.

I changed the water pump two weekends ago and I have great heat now. The old pump had almost nothing left of the impeller blades.

It's not too hard or expensive to replace. I think a new lifetime warranty pump was $40. Took me about 3 hours for the whole project. If you do it yourself, make sure to scrape all of the old gasket off the engine or you may get leaks.

My mechanic wanted $200 plus parts to replace the pump. Glad I did it myself.