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Overheating problem! Help!

joew94th

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About 3 weeks ago my OEM radiator sprung a leak. I have never had a cooling problem until then. Even on hot days, the 360ci in my '66 Belvedere rarely went above 190 degrees. I decided to replace the radiator with a brand new universal fit aluminum cross-flow radiator from Summit. I also replaced the flex fan with an electric one. I installed new hoses and a 160 degree thermostat, 50/50 mix of antifreeze & water. Everything is fine at idol, about 190 degrees after 10 minutes. The thermostat seems to open at the right time and I can see the coolant flow, so water pump is working. One trip around the neighborhood and the temp goes up to 250 degrees and radiator boils over. This radiator is about the same dimensions as the old OEM copper radiator. I've read that cross-flows are supposed to be more efficient. The one difference is that I no longer have a shroud. It's hard to imagine a shroud would have that much difference.
Any help is appreciated!

radiator.jpg
 
I would think a clutch fan/engine driven fan would be better, a shroud wouldn't hurt.......maybe.
 
You haven't looked at many overheating threads on here if you think a shroud doesn't help. You're barely able to cool 1/2 of that rad with that little fan. May also have not burped the system completely.
 
Sounds to me like you still have air in the system. If your cross flow radiator is mounted with the pressure cap higher than the engine, the radiator is self bleeding. However, if the radiator is placed lower than the engine, a surge tank or bleed line is required.
 
Let's "boil" ( pun intended) this down to basics: You replaced a system that worked, with a system that doesn't work.
 
The fan is pulling air towards the engine, correct?
 
Maybe should have re-cored OEM rad. worked fine before.....just my 2 cents
 
These guys are correct....that electric fan has to go. I recommend a factory (non-flex fan) stock style fan with fan clutch. Search around for "some type" of a factory fan shroud, modify the hell out of it if necessary so it fits & the fan blades are 1/2 way inside the shroud and your cooling problems will be gone. Also, Just in case you have a big air bubble in your cooling system, a small 3/16" hole drilled in the thermostat or a fail safe type thermostat will let air bubbles out.
 
Agree with some of the other posts.. Go back to what you had that worked fine.
 
stock fan setup cools hemis and 6 packs so I dont think dodge messed up with their factory setup . Go back to original .
 
Just a thought but I have had thermostats that worked just fine until they decided to stop flowing. After an hour of driving, I had one close and filled my puke tank to overflowing. You may have a bad thermostat. Why a 160 degree anyway? I agree with others though. That small fan probably is not doing you any favors. I too prefer a good thermo fan and shroud.
 
We built this one with the Summit cross flow.451 big block using the factory clutch fan, no shroud. Worked fine.
I have had both big and small block engines that took some time to "Burp" the system even with the drilling of the thermostat. Just saying it's possible. Are the hoses new ? Lower hose have a spring to keep it from collapsing ?

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You haven't looked at many overheating threads on here if you think a shroud doesn't help. You're barely able to cool 1/2 of that rad with that little fan. May also have not burped the system completely.
There's no question that a shroud is beneficial for stop and go traffic. They actually serve to hinder airflow at speed. As I stated in my original post, I have the opposite problem. I have no issue when just idling. My issue is when I am at speed. There's plenty of air flowing, but the car is still overheating.
 
Sounds to me like you still have air in the system. If your cross flow radiator is mounted with the pressure cap higher than the engine, the radiator is self bleeding. However, if the radiator is placed lower than the engine, a surge tank or bleed line is required.
Fill cap is above engine and I have a surge tank. I'll check on the air. Maybe I'll park on an hill facing uphill.
 
We built this one with the Summit cross flow.451 big block using the factory clutch fan, no shroud. Worked fine.
I have had both big and small block engines that took some time to "Burp" the system even with the drilling of the thermostat. Just saying it's possible. Are the hoses new ? Lower hose have a spring to keep it from collapsing ?

View attachment 1544162
I was wondering about the lower hose. It's not collapsed when I check it, but it might be possible that it collapses at higher RPM. I'll check that! If that doesn't pan out, I might try going back to the factory fan.
Thanks!
 
Just a thought but I have had thermostats that worked just fine until they decided to stop flowing. After an hour of driving, I had one close and filled my puke tank to overflowing. You may have a bad thermostat. Why a 160 degree anyway? I agree with others though. That small fan probably is not doing you any favors. I too prefer a good thermo fan and shroud.
Yes, I'm starting to question that fan myself. Once I'm absolutely sure I have all the air out of the system, I'll go back to the factory fan to see if it makes a difference. Summit makes a shroud for this radiator, but it's too small for the factory fan. I guess I could make my own, but I'd rather not. As for the 160 degree thermostat, I just thought that opening it up sooner might help with flow.
 
Let's "boil" ( pun intended) this down to basics: You replaced a system that worked, with a system that doesn't work.
Well, no! Not quite. I replaced a system that wasn't working for one that I was told should work. I might put the factory blade back on though.
 
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