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Old 10-30-2008, 08:42 AM   #1
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Default car heat issues

symptoms

1. car starts, gets up to temperature, heat comes on slowly, until car fully heats up, then heat goes away, and i get no heat inside at all. (seeing as this morning it was in the teens.... i need it)
car runs pretty cold when this happens

2.car then sometimes decides to run hot, like almost near H symbol on dash, but never overheats. and i still get no heat.....


so any ideas boys? i dont wanan go throwing moneys at it unless i know what the problem is.

my guess, thermo, but i dont know enough about the miata heating system to make a valid assumption,

and btw, i really hope the heater core isnt clogged or somthing, i dont want to tear apart the dash (thats where it is right?)


thanx for any help
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Old 10-30-2008, 10:32 AM   #2
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Have you made any upgrades to your cooling system? Such as radiator or a reroute?
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Old 10-30-2008, 10:39 AM   #3
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Quote:
2.car then sometimes decides to run hot, like almost near H symbol on dash, but never overheats. and i still get no heat.....
would you not consider that overheating?


what's your coolant level look like?
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Old 10-30-2008, 11:24 AM   #4
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I say coolant level. Thing is probably empty.
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Old 10-30-2008, 11:45 AM   #5
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I say coolant level. Thing is probably empty.
I agree, once the thermostat opens there is'nt enough water to fill the heater core. And to ad to the problem if there is'nt enough water to steadly pass over the sender it is'nt giving you a true reading. when it was almost on h it was probably reading steam.
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Old 10-30-2008, 12:16 PM   #6
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If you have not modified ANYTHING on the heating system. First flush out the heater core by running water into one hose and draining the other to the ground. Then fill the system with the front of the car elevated and run it until the thermostat opens and you see circulation at the top of the radiator. Squeeze the top hose violently to remove air. Fill to the top of the radiator and put on the cap with the reservour filled to the top line.
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Old 10-30-2008, 02:18 PM   #7
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1. Coolant system is unmodified

2. First thing I checked was coolant level, its fine, when car gets hot, coolant resivour fills up to top



I will flush the system asap, should I change the thermo?

Keep the great ideas comming guys
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Old 10-30-2008, 03:55 PM   #8
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I would change the thermostat. The OEM 2-stage would be best. Sounds like there is a restriction in the heater core/hoses(read blockage or pinch) that is allowing almost all the water to bypass the heater when the t/stat opens; starving the back of your engine of cooling.
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Old 10-30-2008, 05:29 PM   #9
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Originally Posted by olderguy View Post
I would change the thermostat. The OEM 2-stage would be best. Sounds like there is a restriction in the heater core/hoses(read blockage or pinch) that is allowing almost all the water to bypass the heater when the t/stat opens; starving the back of your engine of cooling.
thats the one that sits up front?
or is there one on the back of the head
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Old 10-30-2008, 06:36 PM   #10
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If everything is stock, you have only one thermostat; at the front of the head. When it opens, if there is resistance to flow at the heater core, most of the flow will go from the pump through the thermostat, through the radiator, and back to the pump; effectively limiting cooling to the back of the engine and not heating the passenger compartment.
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Old 10-31-2008, 09:52 AM   #11
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interesting, so how to do i fix this?

i hope ur not going to tell me to take out my heater core and check it for clogs.....
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Old 10-31-2008, 10:34 AM   #12
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Originally Posted by urgaynknowit View Post
interesting, so how to do i fix this?

i hope ur not going to tell me to take out my heater core and check it for clogs.....
Disconnect both hoses and run a water hose to one and flush it out. If flow is still low, get a small submersible pump, set up a loop to a basin and run some flush radiator stuff to clean it for a couple hours.
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Old 10-31-2008, 01:26 PM   #13
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thats a great idea, thanx alot, gives me somthing to do over winter, this things comming off the road in 2 weeks anyway, ill just not drive it, i have a jeep sitting in the driveway for winter time, this miata has yet to see any snow in its 19 years of life.
i doubt it will see any though
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