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Overheating Question

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Old Sep 26, 2007 | 06:13 PM
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Default Overheating Question

Whie driving my 69 427/435 the temp stays normal in the middle of the gauge for maybe 15-20 minutes. Then all of the sudden it just goes very close to the red. It then starts spewing coolant out of the expansion tank. The motor is fresh and the fan seems to be working fine. Any ideas???
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Old Sep 26, 2007 | 06:33 PM
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Sounds like air trapped in the engine coolant system.
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Old Sep 26, 2007 | 09:07 PM
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Originally Posted by Steve 427
Whie driving my 69 427/435 the temp stays normal in the middle of the gauge for maybe 15-20 minutes. Then all of the sudden it just goes very close to the red. It then starts spewing coolant out of the expansion tank. The motor is fresh and the fan seems to be working fine. Any ideas???
Thanks

I installed a Morroso higher filler point in place of the goose neck thermistat housing. I run my over flow cap up on top and have a non blowby on the radiator.

Last edited by gkull; Sep 27, 2007 at 10:27 AM.
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Old Sep 26, 2007 | 10:50 PM
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Originally Posted by dannyman
Sounds like air trapped in the engine coolant system.
Just let it cool, top it off, and go for another drive. It might take 3 to 4 times before you get all the air out.
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Old Sep 27, 2007 | 07:31 PM
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What size rad-cap do you have??? Mine used to boil over. Then I changed the cap to a 18 lbs. cap with a pressure release. It stopped the boiling over when I stopped and turned it off.
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Old Sep 27, 2007 | 08:15 PM
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I drilled a small hole (1/16) in the thermistat unit. This allows the air to escape from the block and does not affected engine temp.
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Old Sep 27, 2007 | 09:26 PM
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Is it air or a bad thermostat ???
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