'92 Mazda 323 Heating coil Air logged?....


Old 12-26-04, 05:51 PM
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Cool '92 Mazda 323, no heat

I have a '92 mazda 323 with 180 K's, automatic transmission 1.6L engine and I have no heat, but the fan IS working.
When the car is idling or i slow down there is cold air coming out of the vents and if the car is reving up (high RPM's) I have SOME heat coming out. I have flushed the cooling system as rad fluid was orange (rust colour).
While troubleshooting i have isolated the problem to the lack of flow through the heating coil. I have disconnected one of the hoses from the firewall and found that fluid was trickling out of the coil, once i opened the radiator cap, much more fluid poured out. I'm guessing this means that that path is not blocked. I then re-connected this hose and disconnected the second, blew air into the coil and cooling liquid came out of the engine. By doing this I checked to make sure the entire system is free of blockage (or so i thought ) After running the car for a while the 2 hoses going to the heating coil are still cold, one somewhat warm and the other cold;(the engine is normal temperature according to the temp. gauge) I am begining to wonder if the cause of my problems is an air pocket somewhere in the system, thermostat or some "mysterious" valve that i am overlooking.

I thank you for your help in advance and hope everyone is enjoying their holidays.
ps. the minus 20 degrees celcius something weather in Ontario isn't helping my pains very much.

Last edited by Euge; 12-26-04 at 06:33 PM.
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Old 12-27-04, 05:03 AM
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Back flush the heater core several times. Check or replace the thermostat and gasket. That rust is in the whole system so all the hoses,engine block,radiator need to be flushed also.

1) Drain coolant
2) Remove the thermostat and re-install the thermostat neck.(with out thermostat)
3) Add a GOOD coolant flush to the radiator with water. Let vehicle run for awhile.(The longer the better)
4) Drain and flush system out with water.
5) Install new thermostat and gasket.
6) Now back flush HEATER CORE several times
7) Add coolant and re-test Heater Core operation.
Old 01-04-05, 06:19 AM
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I have a similar situation to Euge's. I appreciate your input. Would like to carry the discussion a little further. I have a 1993 Nissan Quest (AT, 130K) (Mercury Villager twin) with same symptoms as Euge's. A reliable shop performed the steps you recomended - last winter - twice. Afterwards the car would get cool at stop lights. The shop reported next step would be to replace heater core. We have had a mild winter so far and have been ignoring the cool down - until lately it has gotten much worse (winter and cool car). My questions: How does a heat core go bad? Slowly get gummed up? Is back flushing only a temporary fix for a heater core that is going bad? My Quest has the rear heat and AC. Is there a second heater core hiding back there? I don't get any heat in the back either. Are the two heater cores tied - if one's bad the second won't work? Could lines between the two be clogged? I imagine that getting to the rear heater core would require taking the whole car apart. (?) Also guess that large part of heater core replacement cost is getting behind the dash - true?

Thanks for your help!
Old 01-04-05, 08:16 PM
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The two reasons the heater core go bad that I have seen is either and hole in core or stopped up. Most of the time you will see rust or mud like substance in the cooling system. Most of the time here is two heater cores front and rear but ussually the hose split from front to rear. Flushing is a fix most of the time if the system is not contaminated to bad. One heater core should work with out the other. Check the hoses or lines before both of them. Trim panel ussually on the rear heater core and dash on the front have to be removed. Costly Repair! Hope I answer all questions.
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