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Discussion Starter · #1 ·
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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Discussion Starter · #8 ·
Get a new Radiator....

I had the same problem back in 1989 with my 1978 Magnum GT...It was doing like your car..I changed the thermostat and no difference(I didnt change as many parts as you but)...I had the radiator checked out /cleaned at a well known shop, they said it was fine..Car still overheated !!! Wasnt impressed,as I spent money I didnt have (hey I was young)..

The next day,I went to local performance shop where there were always Mopars parked around and a few guys came out and they checked my car out (being a rare model and them Mopar guys) They said get a radiator,I guess the look on my face they knew I was broke lol..Lucky me I was young enough they helped me out big time !!! They actually gave me a old radiator for free,I just pulled it out of a parts car they had and put it in my car and I never had a problem with it ,car ran cool for years ! I even used their tools and coolant !!!! I returned about 2 weeks later and offered them some money,they kindly said NO ! But,I got a job with them and was there for many years ! Maybe they hired me because I bought them a case of Beer when I went back ,and I was under age lol..Hey those days guys drank at the shop !!

I even had a radiator recored on another car after it was leaking and it still was overheating. Get a new one thats the problem,easily done and they are not that expensive ! These cars stay cool even on hot 100 degree days in traffic !

Good Luck..
I always enjoy the stories I find on these forums. :) I do have a 76 Gran Fury Sport Suburban sitting out back, I didn't really want to rob parts off it but I may grab that radiator and put it in the car to test. Sounds like you've already learned from what I am going through right now, thanks for the knowledge!
 

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Discussion Starter · #9 ·
What engine do you have?

Before replacing the radiator, you might check the fan clutch. If it's lost viscosity, it might not be spinning the fan fast enough.
It's a 360 with small "RV" Edelbrock cam/intake/carb, nothing crazy. I forgot to mention that, I checked the clutch as well, it spins up nicely as rpms increase. Good thing to remember checking, I've had a fan clutch issue on a 90's Dodge truck that had me stumped, thanks for the tip.
 

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Discussion Starter · #10 ·
What engine do you have?

Before replacing the radiator, you might check the fan clutch. If it's lost viscosity, it might not be spinning the fan fast enough.
Could also be scale built up in the block, especially if it has drain plugs for coolant that have never been used.
Had a slant-6 that had never had the block drain open, had to hammer a nail through the scale under the plug to get it to flow. Then the coolant came out like chocolate.
That is entirely possible I guess, since I have had it (6 yrs) I have been careful to have a proper antifreeze mix in it, but the last owners might not have been so careful. I looked at the drain but labeled it a last resort, kinda tricky to get to. I did a Prestone coolant system flush last fall and did get a ton of nasty crap out of both the block and radiator, but it ran very clean after that, even after a second dose of cooling system flush designed to eat that stuff away. Could it be so scaled up that the flush kit couldn't even eat away all the way?
 

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Discussion Starter · #11 ·
My Dad has a '75 Fury with the 360. Compared to the 318 in his '72 Charger, it ran hotter. I'm guessing the radiator even when new barely could keep the engine at proper operating temperature. Just my observation.

I'd suspect a scaled up radiator if it overheats or gets hot at low speeds and stay relatively cool at highway speeds. Had those symptoms with a '92 Acclaim 2.5L I had - the gauge would show normal at idle and climb to 3/4 at highway speeds. A new radiator cured it.
The thing is, it pegs out even going down the road with heat on blast. My car has the "heavy duty" factory radiator, but I guess it's just past its expiration date, the insides of it do look pretty skanky, even after a coolant flush additive. Thanks!
 

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Discussion Starter · #13 ·
That's a sign the radiator simply cannot displace the heat adequately. I meant to say my Dad "had" a 75 Fury back in the day. He sold it long ago and has since passed away. As Bob Lincoln posted, it is also possible the block has scaling that cannot be removed with a flush.
This is a photo of the inside of the radiator... Look screwed?
 

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Discussion Starter · #17 ·
You're getting VERY little flow through those tubes. Time for a new radiator.
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?
 

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Discussion Starter · #20 ·
Make sure that it's the same radiator, or at least that it lines up with the hoses and fittings.

I second Bob's recommendation to remove your block plugs to drain the coolant more completely. When I did this on my Dakota, it wasn't as congealed as what Bob described, but it came out brown for several flushes. Even if you can only reach one side, that's far preferable to leaving all of the gunk inside to potentially clog your system after you drain it. It's easier to get to mine from under the vehicle, so you might want to try that.



The latest radiator for my Dakota was $120 plus tax at Advance, and they had it in stock. If you determine that the radiator needs replacing, research for the best price.

If you remove the thermostat, replace it. Make sure it's the temperature that your owner's manual calls for.
Checked the 76 Plymouth radiator, it won't work, it's a 440 so top inlet is on the wrong side. I'll look into the drain plugs on the block a bit more, but as of right now it looks like it's time for a new radiator. I'm going to check with a few mopar guys around here to see if they have a radiator laying around I could slap in to test. I boiled my thermostat, and at 194 water temp it opened, it's I believe a 190 thermostat so that'll work. Trying to throw around the idea of getting a larger aluminum rad that will support engine mods down the line, but hard to justify the extra 100 bucks. Thanks again for the continued assistance!
 

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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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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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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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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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