Heating issue.
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Cross-Country
Joined: Jun 2020
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Heating issue.
Gentlemen & Ladies
The heat in my '78 F150 is seriously lacking. This summer I had the heater box assembly out, I cleaned it up, replaced the core, & reinstalled successfully. The BTUs were cranking out. Now, come the time I need heat, it is abysmal. To skip some trouble shooting on your end; the fan works, both cables are connected & functioning, both the supply & return lines get hot, & I flushed it out last month trying to get some darn heat. This is not an AC vehicle just the standard box with a core & fan. The flush I did last month seemed to restore some heat temporarily but it's back to blowing colder air. The fact that both the supply & return get hot tell me that fluid is at least circulating. Would a partially clogged core make that much of a difference in heat production? I don't really know what else it could be but I turn to the collective wisdom & experience to see your thoughts. Thank you all!
The heat in my '78 F150 is seriously lacking. This summer I had the heater box assembly out, I cleaned it up, replaced the core, & reinstalled successfully. The BTUs were cranking out. Now, come the time I need heat, it is abysmal. To skip some trouble shooting on your end; the fan works, both cables are connected & functioning, both the supply & return lines get hot, & I flushed it out last month trying to get some darn heat. This is not an AC vehicle just the standard box with a core & fan. The flush I did last month seemed to restore some heat temporarily but it's back to blowing colder air. The fact that both the supply & return get hot tell me that fluid is at least circulating. Would a partially clogged core make that much of a difference in heat production? I don't really know what else it could be but I turn to the collective wisdom & experience to see your thoughts. Thank you all!
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Cross-Country
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This truck does not have a/c. It's just a cable to switch from outside air to the heated air & the cable to change from defrost to heat. Both cables are connected & functional. I checked them today because it occurred as an afterthought. No luck. I think I'm going to have to flush the core more thoroughly & install a filter on the supply line. 😕
Logistics Pro
Joined: Oct 2006
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From: East Central Ia
Set your function lever to off and turn blower on high. If you get air movement from floor vent your blend door seal is leaking. A plugged core only needs 1 fin in the core open to make the hoses both hot but you said great BTU when it's warm out, so I would lean towards leaking blend door. As DB said about Tstat, what's your temp gauge reading?
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Cross-Country
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5851a the blend door seal is good but thank you for that check. I'd not heard of or thought of testing it like that! TStat was changed to a 180° a few months back. Wish I had stuck with the 195° but I only have the dummy gauge to check temp. With the 180° tstat it still reads into the normal operating range. Not as far as the 195° but still far enough into it I'm comfortable running it. I will be changing back to the 195 when I'm able but I usually have to do the work outdoors.
tbruz the level should be good but I will check it again to be sure it isn't that. If someone could confirm something I read about the level in the radiator being approx 1" below the top is where you want it that would be great.
Thank you all the responses.
tbruz the level should be good but I will check it again to be sure it isn't that. If someone could confirm something I read about the level in the radiator being approx 1" below the top is where you want it that would be great.
Thank you all the responses.
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More Turbo
Joined: Jun 2015
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From: New Hampshire
Good news is IF you need to go the replacement route, a heater core replacement on a Non-AC vehicle is a pretty easy job.
Sounds like you've already done the heater box R&R one time as well, so your learning curve is high and the cost of a new core is low.
tbruz
Sounds like you've already done the heater box R&R one time as well, so your learning curve is high and the cost of a new core is low.
tbruz
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I have a 190º in my heater-only truck, but the heat is barely adequate. It started doing that after I put in a new radiator, so I replaced the thermostat expecting to find a 180º, but the old one was a 190º too. I'll have to look more into that blend door. I know I took the cable tether loose, and made sure that the control could move the door to both ends of its travel, just to be sure that wasn't it.
What about heater core restrictors? I know Ford used them in Fox bodies, but I thought it was on the supply side, to buffer any surges due to rapidly increasing water pump speed.
Perhaps a restrictor on the output side might prevent the coolant from coursing through the core too quickly, thereby giving it a chance to dissipate more heat to the cabin?
The restrictors are simply a little 'plug' with a hole in it, or bushing, which gets pushed into the heater hose, where it connects to the core. It steps down the diameter of the hose.
What about heater core restrictors? I know Ford used them in Fox bodies, but I thought it was on the supply side, to buffer any surges due to rapidly increasing water pump speed.
Perhaps a restrictor on the output side might prevent the coolant from coursing through the core too quickly, thereby giving it a chance to dissipate more heat to the cabin?
The restrictors are simply a little 'plug' with a hole in it, or bushing, which gets pushed into the heater hose, where it connects to the core. It steps down the diameter of the hose.
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@meangreen92 I know there is nothing currently in the supply or return hoses acting as a restrictor. Would putting one on the return side cause the heat in the core to get too hot? It is just a radiator in a plastic box. I wonder. This weekend I am going to flush the bejeesus out of the heater core again & install a home made filter on the supply side. Hopefully this will do the trick. I hate re doing work I've already done!
Logistics Pro
Joined: Oct 2006
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From: East Central Ia
Just swap hoses at the core. I used to have to do that on an old Montego, previous owner used plenty of stop leak on the radiator leak. I was afraid to do much vigorous flushing of the old core. It did work.
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Cross-Country
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So this past weekend I flushed the heck out of my heater core. I also got the brilliant idea to put a home made filter on the supply line for the core & I put a screen over the supply from the radiator. This went about as you would expect it to go & after a short drive I removed both. However, after I topped off my fluid levels & continued the trip my heat is cranking once again. Thank you all for the suggestions & trouble shooting ideas.
Laughing Gas
Joined: Nov 2013
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From: S.E. Louisiana;so far USA
The Ford Owner's Manual for my 1976 says to fill coolant to 1 to 1-1/2 inches below the bottom of the filler neck. (page 84)
Hotshot
Joined: Feb 2004
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From: The Shenandoah Valley
But one can put a coolant recovery cap on it, run a hose from the overflow to a recovery tank, and it'll stay fuller. The recovery cap will let the cooling radiator pull from the recovery tank.