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I've had my mustang for about 5 years now and I have been through at least 5 radiators in that time, but I recently did a engine swap from a 289 to a 302. While the new motor was put in I also upgraded to a Aluminum radiator with a Electric fan. (I believe the Radiator is two row.) The new radiator thus far doesn't seem to hold up to the new motor's demands though. When the radiator was first installed the motor ran for about an hour in the garage, and everything appeared to be good. After driving at speeds of around 70 for about 30 minuets its obvious the fan and radiator are not keeping the motor cool, even driving at low speeds yields the same result. The car does have AC but I don't bother running it so as not to put stress on the motor. Just the other day while driving down the four lane I saw what I thought was smoke, but turned out to be steam shooting out of the radiator overflow tube.

Any advice would be appreciated.
 

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How many CFM fan? Does it have a shroud? I run a two row ECP aluminum radiator and a 3300 CFM flex-a-lite fan with no issues. Also have a separate trans cooler with a small Spal pusher fan and a coolant overflow reservoir.
 

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What temperatures are you running at extended idle and cruising speed? The radiator may have puked due to it being over filled. There needs to be head space to allow for expansion. A fan is not necessary at hwy speeds, refer back to temp questions.
 

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I run a 302 in my '66 with no cooling issues. I've owned the car for 23 years and have never overheated. After reading so many of these overheating threads, I have generally found that the further owners deviate from stock cooling systems, the more issues they have. My engine was rebuilt about 4000 miles back, so I know it's clean and flowing well. I have a 3 row conventional radiator with a 6 blade fixed fan and shroud. Everything else in the cooling system is stock. I did installed a 185* thermostat and a coolant recovery tank. I also run an all aluminum top end: Heads, intake manifold and carburetor (Aluminum 670 Street Avenger).
This summer was no different than any other where I live. The temperatures routinely reach 100- 105*. I can operate in those temperatures all day with the A/C running and have no worries about overheating.
 
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What temperatures are you running at extended idle and cruising speed? The radiator may have puked due to it being over filled. There needs to be head space to allow for expansion. A fan is not necessary at hwy speeds, refer back to temp questions.
Good points. Just because it's dumping a little coolant, doesn't imply overheating.
 

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The most common reason for overheating is probably fan shrouding/airflow, followed by incorrect timing, followed by bad thermostat, followed by "I put the head gaskets in backwards".

However, given that it idles okay, I'm guessing you got the head gaskets right. Ditto the thermostat, because if that was stuck closed, it would overheat at idle too. So that leaves either insufficient radiator for your engine, or maybe a weak cooling fan (which would show up more in stoplight traffic than at highway speeds). Or, maybe your timing is off. That'll definitely do it!
 

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Assuming there isn't something wrong with your 302 there is so little difference between a 289 and a 302 I would say your new radiator and fan were not an 'upgrade' at all but exactly the opposite. I drive our '66, 289, automatic, (always) using its A/C anywhere within 1,800 miles of here and it never overheats with a stock, 2-row, brass radiator and factory clutch fan. Its entirely factory stock which means a nearly useless shroud, etc.

As was already mentioned: I have generally found that the further owners deviate from stock cooling systems, the more issues they have.
 

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Did you give the new motor a power flush before fitting?
Who knows how much crudd is in the block choking up the radiator restricting flow.
Why so many radiators? Where they all blocked?

Like Ivy both my cars have a stock setup (one with 3 row alloy rad) no shroud and not even a clutch fan, both run beautifully.
 

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The question no one has asked to far comes to mind. How did you determine your engine has been overheating?. Your engine should run in the 200* range on a normal basis. You need to check the engine temp with an infrared temp tester. A stuck thermostat could give you a high engine temp with a lower radiator temp. If you're getting fluid being pushed out the top of the radiator, rent/get a radiator tester and see if you're pressurizing your coolant system (indicating a leaking gasket or cracked head).
 

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Discussion Starter #10
Thanks for your guys Input I made checked over things again and I noticed a crack in one of the hoses to the engine, I replaced it and got a larger fan and she runs great thanks for the help.
 
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