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Hi everyone, I just joined and am really needing a good logical answer to why my 71 GTO 400/400 is spewing a little overflow after running 5 minutes or so. It is not a violent overflow like overheating but an annoying 2 or 3 ounces. I have replaced the radiator cap and also put in a new Delco thermostat and neither has solved the problem. I was thinking that maybe I could just add and aftermarket overflow jar and correct it but that would not be original.
I have an original car with only 54,600 miles and am trying to keep it that way.
Any help or thoughts would be greatly appreciated
Thanks.
 

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Not that familiar with the '71s, but if there is no overflow jar there will need to be an air gap in the top of the radiator. The overflow is for expansion of fluid as it gets hot. Am I missing something?
 

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Welcome to the forum.

You are overfilling the radiator, it will stop once it pukes down to the proper level.
Also you have posted on the test page, I will move your post to the proper page.
 

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Welcome to the forum.

You are overfilling the radiator, it will stop once it pukes down to the proper level.
Also you have posted on the test page, I will move your post to the proper page.
Totally agree with that. The radiator will seek the coolant level that it is comfortable with. I had a similar issue as you in my '71 GTO 400. I'd fill it up, some would puke out. Fill it again with the same result. Finally some one told me that the radiator needs room for expansion when it gets hot. So, I ran it to operating temp. and then shut it off. Let it cool. Took off the cap and the fluid was slightly below the tubes. Filled it to just above the tubes which left about a 2-3 inch space for expansion. Never had a problem since. Sometimes we worry that we don't have enough in it and it won't cool properly, but it does. I also have a '62 SS 409 and had the same problem. Cured it the same way. Best wishes.
 
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