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I once owned many years ago a 72 Demon with a 340. It was doing exactly what yours is doing. New radiators at the time were mostly only available at the dealer and very expensive. I had mine recored which was cheaper in 1980. It fixed the overheating. I believe a new radiator will solve your problem.
 

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Do you think to get me by until the new one comes I could pull the thermostat to help it flow more through, or would that just make the problem worse from moving coolant too quickly through the engine, not so much the radiator?
All removing the thermostat does is change when the overheating problem occurs. In my opinion, it's never a useful option.

Rather than remove the thermostat, I'd spend money on faster shipping.
 

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Discussion Starter · #23 ·
Decided to pull the block plugs just to see if the block was full of gunk too, got about 1tsp of scaly white stuff out of the motor, but nothing horrendously colored - flushed for 30 minutes. They came out suspiciously easy, turns out the guy who had it before me had taken them out and cross-threaded them in, threads are trashed. Just got back home with new plugs, going to put them in soon. Probably not going to fix the problem, but won't hurt to remove what debris from the system I did. Probably going to hook it all up, fill with water, and go for a drive - my town festival is this weekend and I would like to at least be able to drive it into town, it can make it that far. Thanks again to everyone who has commented, I will update again more when I get a radiator for it or if something else transpires.
 

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Might cross-threading the block plugs have caused a leak that eventually caused your cooling system to run hot?

Removing even such a small amount of scale is an improvement. You don't want any of it lodging in your new radiator and causing a similar problem. I'd also recommend a procedure that was described a few years ago on another thread here: disconnect the hoses to your heater core, attach two cut yard hoses to each end, and pour water through one of the hoses, aiming the other to a drain pan. You can attach another hose from the outdoor tap to the cut ones, but don't run the water pressure too high. You want to remove as much crud as possible before installing your new radiator, and the heater core is one of the places it can accumulate.
 

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Discussion Starter · #25 ·
Might cross-threading the block plugs have caused a leak that eventually caused your cooling system to run hot?

Removing even such a small amount of scale is an improvement. You don't want any of it lodging in your new radiator and causing a similar problem. I'd also recommend a procedure that was described a few years ago on another thread here: disconnect the hoses to your heater core, attach two cut yard hoses to each end, and pour water through one of the hoses, aiming the other to a drain pan. You can attach another hose from the outdoor tap to the cut ones, but don't run the water pressure too high. You want to remove as much crud as possible before installing your new radiator, and the heater core is one of the places it can accumulate.
I don't suspect they were leaking before, there was just an obscene amount of loctite on them to hold. I did use a flush kit on the heater lines to blast out the block and got some nasty stuff out. The heater core just got back from being repaired and cleaned, I just gave it a gentle flush with the hose to get anything out that might have accumulated in the 20ish miles I've driven with it back in. I'm gonna have to either do what he did (I'd rather not risk the sketchy repair) or find a tap to clean the threads up in the block to install my new plug. Regardless, everything should be cleaned out now and ready for the radiator when it comes. Sounds like it will be late next week before it comes, so I am stuck until then. I really do appreciate all the tips from the forum, it's awesome!
 

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If it is indeed the radiator, about the only temporary thing you can do is to put the heat on full hot with the blower on high. The heater core actually functions as a small radiator.
 

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'm gonna have to either do what he did (I'd rather not risk the sketchy repair) or find a tap to clean the threads up in the block to install my new plug.
I vote for tap. Someone else will have to provide the correct size.
 

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Discussion Starter · #28 ·
Well, great - got my radiator today and as I was filling the radiator, I discovered it was leaking between the fins and the plastic bottom tank... Out it comes, the next one will be here on the 11th, a full week from tomorrow. Was hoping to enjoy the car for the 4th, but that's out the window now. Nothing's ever easy! I'll update when I get the new one...
 

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Might cross-threading the block plugs have caused a leak that eventually caused your cooling system to run hot?

Removing even such a small amount of scale is an improvement. You don't want any of it lodging in your new radiator and causing a similar problem. I'd also recommend a procedure that was described a few years ago on another thread here: disconnect the hoses to your heater core, attach two cut yard hoses to each end, and pour water through one of the hoses, aiming the other to a drain pan. You can attach another hose from the outdoor tap to the cut ones, but don't run the water pressure too high. You want to remove as much crud as possible before installing your new radiator, and the heater core is one of the places it can accumulate.
A friend had the heater core clog up in his 59 Savoy. Flushed the heater core by removing both hoses filling it with water and alternating between blowing in each hose which will agitate any debris.
 

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Discussion Starter · #30 ·
Got my replacement radiator yesterday and got it put in. I idled it for about 155 minutes and took it about 4 miles, seemed to hold its temperature alright - before, I would be nearly pegged out. That seemed to do the trick! However, since the tranny cooler lines did not line up with the original, I had to bend them to fit. Tried to be gentle, but I must have kinked one and put a hole in it - by the time I got back from my test run, the whole engine bay was covered in ATF... The fun never ends. I think I will try to flare the end of the line before the break and run rubber line close to the radiator. The question is, what type of ATF do I go with? From what I have read, ATF+4 is what Mopar recommends for TorqeFlites to replace the old Mercon stuff, thinking I will go with that unless you guys know otherwise. Hoping my overheating is resolved and I can now cruise the car once I get the tranny issue solved. Thanks again.
 

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And if you splice the trans cooling lines with rubber hose, be sure to buy special oil-resistant hose for the purpose, with fuel injection band clamps. Otherwise, in about 3-5 years, that hose will disintegrate, and your transmission will run dry.
 

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Hey all, I've had a 75 Cordoba for a while now and have battled overheating issues the last several years. I've replaced the water pump, radiator hoses, thermostat (and boiled to check, it's working), had heater core redone and cleaned, had radiator repaired and cleaned (told it's in very good shape by reputable radiator shop), did the paper test to check fan (it pulled very tightly on radiator), replaced intake manifold gaskets, two different new radiator caps, timing is dialed in to proper spec (both mechanical and vac advance), air/fuel seems to be good, done full block and radiator flush kit (did get a lot of crap out of it), have OE shroud and good OE fan on it, and have ensured all air is out of the system, extensively burping any and all air out of it... I'm basically at a loss of what to do. I can drive the car 5-10 miles before the temp gauge gets to over half, and if I turn around and go home that far, I am pegged out on a warm day. Thermometer to intake/radiator shows upwards of 250-260 coolant temp when pegged so I know the gauge is correct, though I rarely let it get that high. Even blasting full heat (hotter than the surface of the sun) the car will still overheat. The car runs great aside from the overheating, I'd love to take it on longer trips but am unable to due to the issue. I've covered all the things I can think of that would cause the overheating, but the issue persists. Any ideas would be greatly appreciated. Thanks, Tyler.
Hey all, I've had a 75 Cordoba for a while now and have battled overheating issues the last several years. I've replaced the water pump, radiator hoses, thermostat (and boiled to check, it's working), had heater core redone and cleaned, had radiator repaired and cleaned (told it's in very good shape by reputable radiator shop), did the paper test to check fan (it pulled very tightly on radiator), replaced intake manifold gaskets, two different new radiator caps, timing is dialed in to proper spec (both mechanical and vac advance), air/fuel seems to be good, done full block and radiator flush kit (did get a lot of crap out of it), have OE shroud and good OE fan on it, and have ensured all air is out of the system, extensively burping any and all air out of it... I'm basically at a loss of what to do. I can drive the car 5-10 miles before the temp gauge gets to over half, and if I turn around and go home that far, I am pegged out on a warm day. Thermometer to intake/radiator shows upwards of 250-260 coolant temp when pegged so I know the gauge is correct, though I rarely let it get that high. Even blasting full heat (hotter than the surface of the sun) the car will still overheat. The car runs great aside from the overheating, I'd love to take it on longer trips but am unable to due to the issue. I've covered all the things I can think of that would cause the overheating, but the issue persists. Any ideas would be greatly appreciated. Thanks, Tyler.
 

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Hi, I own a 76 Cordoba with a 400, the rad was pretty half way block with poopies, flush it many times, still, so much crap in it, got it rebuilt, with bigger pores in it, replace the water pump, 180 Thermostat, new Clutch fan, the temp. gauge when up to half or more, now it's up only pass a 1/4, even in traffic, stay's cool even on hot and humid days, I cruise about 75 MPH on highways, still it's cool, I use Preston Premix, since then it's been running Great. Hope this helps.
 

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I have a 76 Cordoba with a 400, ac, My engine got very hot too, needle when't over half way mark, got the rad rebuilt with bigger pours in it, now it goes to a 1/4 or little over, heaven in hot days and in traffic. Good luck.
 

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Didnt the OP say a rad shop cleaned the rad and said it was in good shape?
Yes, though there was a picture looking through the cap opening and it was still scaled up.
The OP did replace the radiator which solved the problem. The 400 in the Cordoba had a single core radiator that didn't have much margin for error.
 

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I think I would find a different radiator shop.
Heck a 318 needs a 2 row unit.
You know, the 400 may have been a 2 core? It's been years since I had one. But as soon as it started to scale up, the car wanted to run hot. I wondered if the HP 400 got a better radiator than the regular 400.
 
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