Heater Core Leak

XR7-4.6 said:
The gasket is sandwiched between the firewall and the heater box and larger in size than the hole the core passes through.
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That is correct and makes it a b*tch to insert new core. Even when lathered w/ dawn detergent. I wound up cutting mine on side near fender to give more room as the core goes straight in according to the slot in box. Thankfully I've only had to do this once in 381k miles.
 
Generalee0527 said:
That is correct and makes it a b*tch to insert new core. Even when lathered w/ dawn detergent. I wound up cutting mine on side near fender to give more room as the core goes straight in according to the slot in box. Thankfully I've only had to do this once in 381k miles.
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Yeah that’s the worst part of the job to me, I’ve had to do the same thing. It’s actually not as bad as the 3.8 cores that do have the splayed out outlets, I really felt like I butchered the gasket in my friends SC getting that one in!😬
 
I drilled a tiny hole into the bottom of the heater core housing. About another half cub of coolant came out.

For those of you who have done this, is there usually coolant pooling up in the evaporator housing? That seems to be the lowest point, but I'm not comfortable drilling into it. I'm worried that the evaporator is swimming in coolant.
 
1997ThunderbirdLXV6 said:
I drilled a tiny hole into the bottom of the heater core housing. About another half cub of coolant came out.

For those of you who have done this, is there usually coolant pooling up in the evaporator housing? That seems to be the lowest point, but I'm not comfortable drilling into it. I'm worried that the evaporator is swimming in coolant.
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If there was any fluid discharged into the evaporator housing it should have drained out the drain port through the firewall the same way excess condensation from using the A/C would.
 
Wait, now I'm thinking: doesn't the evaporator housing have a drain hole for condensation that comes out forward of the firewall?

Maybe my last post should be moved into the stupid questions thread...
 
1997ThunderbirdLXV6 said:
I have to say that my A/C has never been this cold before. I'm guessing that, even with the blend door set at full cold, a 200°F heater core in the immediate vicinity of the airflow always caused some minor heating.
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Yep, you can feel the heat from it through the vents with AC off and the temperature set to max cool too, it’s always warmer than the outside air being pulled in through the cowl. The HVAC in these cars leaves a lot to be desired
 
I managed to download the original instructions from the old site as a pdf. Not sure if I can do this but I'm going to try to add an attachment.

I still have the photos I took when I did mine (they won't shown on the old site as I've deleted the Google album). I can post them here if that would help?
 

Attachments

XR7-4.6 said:
Yep, you can feel the heat from it through the vents with AC off and the temperature set to max cool too, it’s always warmer than the outside air being pulled in through the cowl. The HVAC in these cars leaves a lot to be desired
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Which prompts me further to give this a try: spend the next mild Virginia winter without a functional heater core. There may be a couple of uncomfortable days, but I'm optimistic overall.


Question loosely related to this: when set to DEFROST or FLR & DEF, the A/C is on. Does it  not turn on in these settings below a certain ambient temperature?
From what I could find in the workshop manual, there doesn't seem to be any logic related to ambient temperature. However, apparently there's a pressure switch which turns off the A/C, and low ambient temperature does affect that pressure switch. It's somewhat confusing, plus I'm just typing from memory here; I can screen shot that reference if needed.
 
There is no cutout below a certain ambient temperature, however like you said, ambient temp will affect AC pressures, and when the pressure drops too low, it cuts out the compressor. The result is the AC will be cycling when the temperature drops.
 
Yep that’s basically the purpose of the switch, no need for an ambient sensor/controller when a simple pressure switch and science will do 🙂
 
KevinVarnes said:
Just fix the heater core. The part isn't that expensive and the job isn't that hard.
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I don't disagree. However, I'm considering my personal use case which is A. living in a area where heat is rarely needed and B. actually getting improved A/C performance without functional heater core.
 
1997ThunderbirdLXV6 said:
getting improved A/C performance without functional heater core.
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Where do you get this idea?

HVAC air always passes through the evaporator. Depending on the blend door setting, it may or may not pass through the heater core at all. Having it plugged off won't "improve" A/C performance.
 
theterminator93 said:
Where do you get this idea?

HVAC air always passes through the evaporator. Depending on the blend door setting, it may or may not pass through the heater core at all. Having it plugged off won't "improve" A/C performance.
Click to expand...

IMO even with the blend door shut there’s heat from the core radiating past the blend door into the ducting what you get out of the vents isn’t as cold as it would be with a bypassed heater core. I would not at all surprised if there was a 5° to 10° difference out the vents at full blast.
 
XR7-4.6 said:
IMO even with the blend door shut there’s heat from the core radiating past the blend door into the ducting what you get out of the vents isn’t as cold as it would be with a bypassed heater core. I would not at all surprised if there was a 5° to 10° difference out the vents at full blast.
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This has been my observation exactly these past few days. Outside temperature today reached 88°F, and the interior is the coolest it has ever been.
 
I haven't had any more coolant dripping in several days now. I think the prolonged dripping, even after the heater core had been disconnected, stemmed from the foam layer behind the heater core flap; that layer was soaked in coolant and released it very slowly.

See here on an equivalent Mark unit from TBSCshop:
Screenshot_20250929_173852_Samsung Internet.jpg

Meanwhile, I'm enjoying  really cold A/C and also simply fresh, unheated air in PANEL mode. All in all, I'm happy for now...
 
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