Heater box question

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We just took the box apart in my 74, and there was nothing attached to it, hence the reason I'm confused. Also found a crack in the top of the box. I was getting lukewarm air with the box on. Do you know if the assembly of the box would be in the service manual anywhere?
 
buffoni88 said:
We just took the box apart in my 74, and there was nothing attached to it, hence the reason I'm confused. Also found a crack in the top of the box. I was getting lukewarm air with the box on. Do you know if the assembly of the box would be in the service manual anywhere?
Click to expand...

It should be. Lukewarm air I would suspect the thermostat in the engine first
 
Nope, I just threw in a new one. And with the front half of the box off, car running at thermostat temperature, blower on, I'm getting a lot of heat...
 
buffoni88 said:
Nope, I just threw in a new one. And with the front half of the box off, car running at thermostat temperature, blower on, I'm getting a lot of heat...
Click to expand...

Maybe the door in the box that lets in fresh air is not shouting all the way or the foam seal on the door is bad just throwing stuff out there
 
that rod helps hold the heater assembly tight & keeps it from sagging, the hooked end goes over the lip of the vent & you tighten it up inside.

if you do not hook this up the weight of the unit causes it to lean towards the passenger.
Lawrence
 
Yes the “J” hook hangs over the fresh air flange. There should be a foam seal where box contacts this hole. If the existing seal is hard or unserviceable, clean off the old one, and use peal & stick foam strip from door/window insulation section at a hardware or big box home improvement store.

Now would be the perfect time to crack the new box open, clean it out including heater core, and rebuild box’s internal flappers with a kit from Detroit Muscle to like new condition eliminating any internal leaks, and 40 years of built-up crap impeding air circulation.
http://detroitmuscletechnologies.com/
 
VDART said:
that rod helps hold the heater assembly tight & keeps it from sagging, the hooked end goes over the lip of the vent & you tighten it up inside.

if you do not hook this up the weight of the unit causes it to lean towards the passenger.
Lawrence
Click to expand...

Exactly what I was looking for, thank you! Ok, so now on to my next question. With the front of the heater box off, engine at optimal temperature with thermostat open, the heater core is getting warm on the inlet and outlet side, but the middle of the core isn't getting hot. Now, if both heater hoses in the engine bay are hot, that automatically means that I'm getting flow through the core, correct? I turn the blower on, and the air still isn't that warm. I'm debating if I should just replace the core, and get the rebuild kit that wjajr mentioned (thanks for the link, by the way!).
 
My next question: Assuming the heater core is functioning properly, and assuming there are no air pockets in my cooling system...how damaging would a crack in the heater box be? Also assuming the blend air control was working properly. With the front of the heater box removed, heater core exposed, engine running, it's getting hot, but when I turn on the blower it still just doesn't feel hot. If the front of the box were on, would it be containing the heat more and making it hotter? I'm just trying to narrow it down to either a crack in the box, or the heater core not heating up as much as it should. I apologize, I know I'm all over the place, I'm just...my mind is blown. I can troubleshoot highly complicated military jet, but can't even figure out why I'm not getting warm air in my car :(
 
the heater box crack --will only cause air flow problems -- not heat temp problems---

for the heat -- if your heater core is the same temp as the engine side coolant then that is the amount of heat available.

check temp at radiator if your heater core is not that hot --then you have restrictions in the lines.

if you have your box apart --repair the crack, jb weld should suffice.

your box controls air flow.heater core is the same --your box just re-directs air to change temp. Lawrence
 
I suspect that the foam gaskets on the internal flappers are dried out and dead forming little to no sealing. The other cause for low heat output is the heater core being blocked by crud such as leaves, animal nests, and dirt. I was surprised at the pile of crap found in the box when I opened it to replace a leaking heater core, and all the flapper foam gaskets were completely disintegrated preventing any control of hot & cold air flow.

You will cure all your heat & defrost problems with a rebuild kit, and cold weather driving will become pleasurable.
 
buffoni88 said:
With the front of the heater box off, engine at optimal temperature with thermostat open, the heater core is getting warm on the inlet and outlet side, but the middle of the core isn't getting hot. .
Click to expand...

Replace the core. The internal passages in the core are plugged up. The heater core is like a small radiator. There are many small tubes in it, Some of these are plugged.

PS: the reseal kit mentioned, is also a good idea, while the case is out.
 
If you have trouble getting the J bolt to hook over the vent just loosen
the nut on the bottom and back it off some to make the J bolt longer.

When you get it hung, just tighten the nut back up and it will draw the unit
up tight.

Hope this helps.
 
Thank you all for your quick input. I ended up pulling the car into the hangar at work (shhhh...there was no aircraft work that night!), and pulling apart the heater box. Went ahead and put a new heater core in, then assembled the box assembly. The little hole where the blend air hinge fits into was cracked, so I threw some epoxy at it (aircraft grade), and put it back together, now it gets TOO hot! Again, thanks for all of the help!
 
Too hot is good. I like to keep car hot in winter, I call it a poor man’s trip to Florida; it’s a long cold winter in Maine.
 
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