over heat at shutdown - Pontiac GTO Forum
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post #1 of 7 (permalink) Old 02-22-2016, 04:07 PM Thread Starter
 
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over heat at shutdown

my 69 gto 400 is a fresh rebuild less than 500 miles on the complete rebuild. the car runs a little hot but does not discharge any coolant until i shut the car off and then it blows off a lot of coolant. new pump, new radiator, shroud covers the fan, the hoses are new and not collasped. i would appreciate any thoughts or other help. timing seems to be right on
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post #2 of 7 (permalink) Old 02-22-2016, 04:32 PM
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Originally Posted by kensoldgoat View Post
my 69 gto 400 is a fresh rebuild less than 500 miles on the complete rebuild. the car runs a little hot but does not discharge any coolant until i shut the car off and then it blows off a lot of coolant. new pump, new radiator, shroud covers the fan, the hoses are new and not collasped. i would appreciate any thoughts or other help. timing seems to be right on
What is a little hot temp wise?
Rebuilt engines will run a little hot for the first 5-8 hundred miles.
Make sure you have a good cap and don't overfill the radiator, leave a couple of inches or it will spit some out.
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post #3 of 7 (permalink) Old 02-22-2016, 06:20 PM
 
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Start by checking the radiator cap. what psi is it? The cap is often overlooked.
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post #4 of 7 (permalink) Old 02-22-2016, 06:36 PM
 
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I agree with the guys, pressure cap keeps the boiling temp down, bad cap will make the car run hotter, but even if right overfilling the radiator will cause a car to overflow even if all is correct, correct fan couch operation also overlooked and causes it to run hot at idle, then it gets hot and hard to cool off...also correc 50 x50 antifreeze mix is the best...
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post #5 of 7 (permalink) Old 02-24-2016, 09:36 AM
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What these gents said. New engines run a tad hotter, an over-filled radiator will puke when heat soaked due to no room for expanding coolant, and a weak cap will let it puke that much easier. It's amazing how many 15 pound radiator caps open up at about 7-8 psi!
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post #6 of 7 (permalink) Old 02-24-2016, 10:25 AM
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If there is no overflow tank the level should be about 2 inches below plum full when cold.
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post #7 of 7 (permalink) Old 02-25-2016, 05:52 PM
 
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Originally Posted by 70kgold View Post
Start by checking the radiator cap. what psi is it? The cap is often overlooked.
Second that. Had the same issue with my 68. Replaced the cap and all is well.
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