Intermittent heat issues 225 slant

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74Dart_Girl

74Dart_Girl

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New to cars ish, and just wanted to verify a hunch, I get interior heat rarely, and when I do there really isn't a constant that follows.

Its a 74 dart swinger with 225 slant 6 in it,

Im assuming it would be the thermostat causing this?
 
Is this an AC car? Does it have a vacuum controlled heater valve? What is the temp gauge doing all this time, IE does the engine "generally" seem to run "up to temp?"
 
67Dart273 said:
Is this an AC car? Does it have a vacuum controlled heater valve? What is the temp gauge doing all this time, IE does the engine "generally" seem to run "up to temp?"
Click to expand...

no AC heat only, vacuum controlled valve unsure but I don't think so. The engine temp stays consistent regular temp, on long highway drive trips (3 hours or more) it can get quite high on hills and can get consistently warm and has to be monitored.
 
You might have something plugging or even a bad water pump

You have a service manual? I'm guessing no. The latest we have for (free) download is the 73 which should be the same, here at the end of this thread

http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617

More info available from MyMopar

http://www.mymopar.com/index.php?pid=31

If this was originally a NON A/C car, there is no vacuum heater valve. You might have something like a mechanical door sticking. You might be able to open the vent door and look in there and into the discharge chute with a mirror and flashlight and see what the doors are doing with cable movement

Are you getting good airflow with the blower on high? Does the blower "sound" OK? IE run quiet?

Check your heater hoses. They should both be staying HOT with the engine warmed up
 
67Dart273 said:
You might have something plugging or even a bad water pump

You have a service manual? I'm guessing no. The latest we have for (free) download is the 73 which should be the same, here at the end of this thread

http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617

More info available from MyMopar

http://www.mymopar.com/index.php?pid=31

If this was originally a NON A/C car, there is no vacuum heater valve. You might have something like a mechanical door sticking. You might be able to open the vent door and look in there and into the discharge chute with a mirror and flashlight and see what the doors are doing with cable movement

Are you getting good airflow with the blower on high? Does the blower "sound" OK? IE run quiet?

Check your heater hoses. They should both be staying HOT with the engine warmed up
Click to expand...

Yup I have the factory manual for the 74, the hanes, and the body service manual.

I have been through all the ducting nothing is blocked, the airflow is great very strong and consistent, it runs quiet and well. I will check the heater hoses tomorrow when I take it for a run. I was on the coast and it worked for the most part, since I moved to higher elevations I have no more heat :/.
 
Low coolant level would cause similar symptoms,, if not,, I would check/change thermostat,, and back flush the heater core..

hope it helps
 
My 63 dart has the same engine in it and my water pump has 4 hoses coming off of it. One is a pre-thermostat by pass, one for the lower radiator hose, and 2 for the heater core. With this setup the thermostat is irrelevent. I would first test the heater core by disconnecting the hoses from wherever they are connected and run water through it from a garden hose. If the water doesn't flow freely you have a clog in the heater core. I have run into this situation in many different cars and it is usually caused by either significant rust debris or more often someone by someone dumping half a dozen tubes of aluma-seal into the radiator which then gets clogged in the heater core. there should be virtually no resistance in a unclogged radiator or heater core.

I've gotten pretty good success by holding the garden hose and the heater hose together and building up tons of pressure and eventually blowing the clog out. If you really can't get it out then your next bet is to replace the heater core.

lmk if that doesn't work and I'll keep trouble shooting with you, pics would make it real easy. Mine also heats up in stop and go and on hills so i'm going to be installing a additional electric pusher fan on it this weekend which i hope will help.
 
These cars are famous for having a bunch of leaves and crap blocking the air to the heater core also.
 
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