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  #1  
Old 12-13-2013, 12:35 PM
69 Polara 69 Polara is offline
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Default Heater Issue

Got a new project car (71 Dart). Sweet car. The fan works (all speeds) and as near as I can tell the heater box is hooked up (both hoses attached and going into the firewall, right?), but she blows ice cold all the time. There is no AC, by the way.

What should I look for?

Thanks
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  #2  
Old 12-13-2013, 02:48 PM
John Kunkel John Kunkel is offline
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The Dart has no water control valve so coolant circulates through the heater constantly.

With the engine warmed up, feel both of the heater hoses in the engine compartment....they should be hot. If not, the heater core is plugged or there is an air lock in the heater core.

If the hoses are hot the problem is probably a misadjusted (or unhooked) temp control cable, this cable controls the position of a blend door that routes air through the heater core.

In the defrost position is there warm air at the windshield?
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  #3  
Old 12-13-2013, 07:08 PM
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Madman Stephan Madman Stephan is offline
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My guess is also with the coolant flow. It might be very limited or non-existant. If you don't feel heat or vibrations from the flow of coolant on the hose, you'll have to disconnect everything piece by piece and work your way back until you find the restriction.
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Old 12-15-2013, 03:47 PM
69 Polara 69 Polara is offline
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Quote:
Originally Posted by John Kunkel View Post
The Dart has no water control valve so coolant circulates through the heater constantly.

With the engine warmed up, feel both of the heater hoses in the engine compartment....they should be hot. If not, the heater core is plugged or there is an air lock in the heater core.

If the hoses are hot the problem is probably a misadjusted (or unhooked) temp control cable, this cable controls the position of a blend door that routes air through the heater core.

In the defrost position is there warm air at the windshield?
Thanks. I'll be checking very soon and report back.
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  #5  
Old 12-16-2013, 07:41 PM
69 Polara 69 Polara is offline
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Here's the latest...

Defrost blows cold air just like everything else.
The hose from the water pump is quite warm.
The other hose isn't even close to the same temp.

Any ideas?
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  #6  
Old 12-16-2013, 08:19 PM
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Sounds like the core is clogged. You might try reversing the heater hoses to back flush it. Or, you could disconnect both hoses and rig up a garden hose to blow through one nipple and then the other. However, sometimes a core can be ruptured if you are too aggressive with the pressure. Remember that little radiator is 44 years old! Still, with the chance that you could break up the clogs without causing a leak and restore heat, it sure beats changing the core. I don't know if that vintage car would require pulling the dash or not.
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Old 12-17-2013, 02:05 PM
440roadrunner 440roadrunner is offline
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X2 above Also this can be indicative of an air lock. I always pull the heater hose next to the stat, fill the system until I "get water" then hook the core up and top off the system.

Last, it's possible you have something like a pump impeller rusted loose from the shaft. If you are having mild weather there, the engine might be running at fairly expected temps.
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Old 01-04-2014, 03:58 PM
69 Polara 69 Polara is offline
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Does knowing which hose is hot vs. cold help in the diagnosis?
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Old 01-04-2014, 05:35 PM
John Kunkel John Kunkel is offline
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The hose that connects to the intake manifold near the thermostat housing is hot water out to the heater, the hose that connects to the water pump housing is return water from the heater.
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Old 01-06-2014, 04:59 PM
69 Polara 69 Polara is offline
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Quote:
Originally Posted by John Kunkel View Post
The hose that connects to the intake manifold near the thermostat housing is hot water out to the heater, the hose that connects to the water pump housing is return water from the heater.
As soon as it warms up a bit, I'll begin a deeper analysis, but let us presume for a second the problem is the core... We have water flowing in, but there's a blockage. Where does the water go? If it's not getting through the core, wouldn't something spring a leak? Wouldn't something bad happen?

Thanks
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Old 01-07-2014, 03:20 AM
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Probably not. The engine would behave like the thermostat wasn't opening up to allow coolant to circulate through the core. I believe there is a small bypass hose and that vintage car may have a water valve on the firewall that controls coolant that goes through the core. If you can't back-flush it and want heat, then it's time to change the core.
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Old 01-07-2014, 02:54 PM
440roadrunner 440roadrunner is offline
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Here's what I'd do. DETERMINE for certain that there is no water control valve. I think some of the AC cars used them, "non" AC did not.

Follow the hoses from the engine to the firewall. One hose connects to the water pump that is INTO the engine.

The hose as John says above, near the T stat housing is the OUTLET FROM the engine.

Remove the heater hoses at the engine, or cut them if necessary. Take a garden hose and run water through the core OPPOSITE from the engine hook up, IE "backflush"

Once you do that, you'll have to blow some air through the core and get some antifreeze back in, or it will freeze of course.

If you cannot get good flow, there's only two solutions..........

take the core out and take it to get it cleaned if it's in decent condition

or replace the core.


There is one more possibility...............the water pump impeller could be damaged, and the engine could be operating on "convection." In colder weather, it might not overheat, but it sure won't pump through the heater!!!! Only way I know to check that is to slowly warm the engine with the cap off, and look for vigorous flow increase as throttle is opened. Of course you can pull the pump and inspect it.
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  #13  
Old 01-07-2014, 03:48 PM
69 Polara 69 Polara is offline
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Thanks for the tips. As soon as we get above 15 degrees Farenheit, I will get cracking on this. It all seems fairly simple.
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