Possible No flow to heater core?

-
Kannon Herbert

Kannon Herbert

Member
Joined
Jan 31, 2019
Messages
23
Reaction score
11
Location
Oregon
Hi, I hope everyone is doing well. I’ve been taking some time to work on my 225 74’ dart this last weekend, and I’ve encountered something that’s baffled me. My heater currently does not work, and I decided I likely needed a new heater core, but I also decided I would continue with a coolant flush and fill. I wanted to flush the heater core aswell to see if it was getting flow or not, and I also checked the vacuum control valve on the inlet hose. Both seemed to flow well and the valve functioned well. I then proceeded to flush all my coolant, clean with a system cleaner and refill and bleed air. Out of curiosity I checked to see if my heater would now work with a cleaned system, and of course it still did not blow anything but temperate air. I then got out to feel the heater core inlet hose after the car had been running for about 20 minutes, and sure enough it wasn’t warm at all. I’ve looked around but I can’t find any help or answers on why my inlet hose isn’t even receiving coolant at all. I’ve also done a thermostat and gasket replacement so I know it’s not that. Anyone have any ideas? Is vapor lock in the heater core a possibility? Thanks.
 
Last edited:
There are only so many reasons

plugged heater core or even plugged hoses or valve

Non functioning valve, or maybe someone replaced valve with one working in opposite direction

Non functioning vacuum controls

BAD WATER PUMP. Sometimes the pump impeller rusts/ falls off the water pump, and the engine cools somewhat by convection, but circulates no heater coolant
 
67Dart273 said:
There are only so many reasons

plugged heater core or even plugged hoses or valve

Non functioning valve, or maybe someone replaced valve with one working in opposite direction

Non functioning vacuum controls

BAD WATER PUMP. Sometimes the pump impeller rusts/ falls off the water pump, and the engine cools somewhat by convection, but circulates no heater coolant
Click to expand...

alright. I’ll look into the water pump next. Thanks for the help :)
 
If the core is plugged, the inlet hose will be moderately hot while the outlet hose will be cold. Maybe your hoses are crossed?
 
Murray said:
If the core is plugged, the inlet hose will be moderately hot while the outlet hose will be cold. Maybe your hoses are crossed?
Click to expand...

I did flush the core before re-installing all components and refilling coolant, so I’m pretty positive the core isn’t clogged and my hoses are not crossed at all.
 
So if you can get coolant to flow thru the heater core. There must be a blockage elseware.

You could connect the heater hoses together, bypassing the core and see if both hoses get hot.

You could also see if you can blow low-pressure (16lbs) air in both hoses and see which one presureized.
 
Murray said:
If the core is plugged, the inlet hose will be moderately hot while the outlet hose will be cold. Maybe your hoses are crossed?
Click to expand...
This is not always true. Many times both hoses are much colder than engine, and sometimes there is "some" flow. So it varies. Only sure thing is a properly operating heater, both hoses are HOT
 
Since you have a vacuum water valve, is it an ac car? If so are the doors in the heater box all moving when you change from heat to ac to defrost?
 
Mike69cuda said:
Since you have a vacuum water valve, is it an ac car? If so are the doors in the heater box all moving when you change from heat to ac to defrost?
Click to expand...

yes I can hear them moving. I’m gonna take apart the box and see if I can verify that though.
 
If core is flowing properly,and all components are working correctly with engine at operating temperature both hoses should be hot.

fill rad ,pull hoses off core and set them in a bucket. One should flow out, other should suck coolant. Im betting the fittings at block end have corroded shut.

I check for coolant flow by running engine with cap off and coolant a tad low. When t-stat opens you will see coolant moving through rad.
 
our 1st 67 without a/c had no water control valve and very poor heat. It was easy enough to take the hoses off the slant 6 and drape over the right fender. I flushed with garden hose until water ran clear. When I changed flow direction the water ran nasty again. Repeated this several times before water ran clear both ways. My result was toasty.
Thermostat stuck open is a possibility also.
 
I have done the same thing as redfish on a couple of cars, one Mopar and one ford. Both showed an improvement in heating, but the results were not really a dramatic change.
 
When I took my 69 heat / ac box apart it was full of dirt and leaves. That could be your issue also.
 
pull return hose and see if its flowing......air has to go past the core to get heated, perhaps the air you feel is not getting the flow path its supposed to get.

Does it have functioning "A/C bypass valve"? looks like the controller that routes coolant through the core or bypasses it.
 
Last edited:
Mike69cuda said:
When I took my 69 heat / ac box apart it was full of dirt and leaves. That could be your issue also.
Click to expand...

that’s the next step. I bet there’s something in there, it had been garaged for most of its life and it almost smells like something died in the box, as every time I turn on the fan it smells
 
You must log in or register to reply here.
-

Back
Top